Preamble

Photosynthetic Characteristics and Leaf Microstructure of Craigia yunnanensis Seedlings and Saplings

Affiliations:
Guangxi Academy of Forestry; Guangxi Botanical Garden of Medicinal Plants, Chinese Academy of Sciences; College of Tourism and Landscape Architecture, Guilin University of Technology, 541006.

Abstract

Craigia yunnanensis is a plant species with an extremely small population (PSESP) and is listed as a National Class II Key Protected Wild Plant in China. Significant bottlenecks exist in its natural population regeneration. This study investigates the photosynthetic characteristics, photosynthetic pigment content, leaf anatomical structure, and leaf functional traits of C. yunnanensis seedlings and saplings.

The results show that the maximum net photosynthetic rate ($P_{n,max}$) of saplings is significantly higher than that of seedlings ($P < 0.01$), indicating that seedlings are shade-tolerant while saplings are heliophilous (light-demanding). Saplings exhibited significantly higher contents of chlorophyll $a$, chlorophyll $b$, and carotenoids compared to seedlings ($P < 0.05$). Furthermore, saplings possessed thicker leaves, more developed palisade tissue, and larger midrib vessel diameters. They also demonstrated higher specific leaf weight (SLW) and leaf dry matter content (LDMC).

Correlation analysis revealed that $P_{n,max}$ is significantly positively correlated with leaf thickness, photosynthetic pigment content, SLW, and LDMC ($P < 0.05$ or $P < 0.01$). These findings suggest that while seedlings are adapted to the low-light environment of the forest understory, saplings require higher light intensity to support their superior photosynthetic capacity. Insufficient light in the understory may hinder the transition from the seedling stage to the sapling stage, which likely represents a critical factor in the species' endangerment. This study provides a scientific basis for the conservation, introduction, and domestication of C. yunnanensis. Conservation efforts should focus on improving light conditions to facilitate natural population regeneration.

Introduction

Craigia yunnanensis is a relict plant of the Tertiary period and a member of the Malvaceae family. As a species with an extremely small population, it holds significant scientific value for studying plant evolution and phytogeography. However, field observations indicate that C. yunnanensis faces severe challenges in natural regeneration, particularly characterized by a high mortality rate during the transition from seedlings to saplings. Understanding the physiological and structural adaptations of different life stages to light environments is essential for developing effective conservation strategies.

Results and Analysis

Photosynthetic Characteristics and Pigment Content

The photosynthetic capacity of C. yunnanensis varies significantly across developmental stages. The maximum net photosynthetic rate ($P_{n,max}$) of saplings was found to be substantially higher than that of seedlings. This physiological differentiation is supported by the concentration of photosynthetic pigments. Saplings contain significantly higher levels of chlorophyll $a$ ($Chl$ $a$), chlorophyll $b$ ($Chl$ $b$), and carotenoids ($Car$) than seedlings ($P < 0.05$). The lower $P_{n,max}$ and specific pigment adaptations in seedlings suggest an evolutionary strategy to survive in the light-limited understory, whereas saplings transition toward a more productive, light-demanding physiological profile.

Leaf Anatomical Structure and Functional Traits

Microscopic analysis of leaf anatomy revealed that saplings have evolved structures to optimize high-intensity light capture and water transport. Compared to seedlings, sapling leaves are significantly thicker with more robust palisade tissue. The diameter of the vessels in the midrib is also larger in saplings, facilitating more efficient hydraulic conductance to support higher transpiration and photosynthetic rates.

In terms of functional traits, saplings exhibited higher Specific Leaf Weight (SLW) and Leaf Dry Matter Content (LDMC). These traits are typically associated with increased investment in leaf structural integrity and photosynthetic machinery, consistent with plants adapted to higher light environments.

Correlation of Photosynthetic and Structural Traits

Correlation analysis indicates a strong integration between leaf structure and function. $P_{n,max}$ showed significant positive correlations ($P < 0.05$ or $P < 0.01$) with several key parameters:
- Leaf thickness and palisade tissue development
- Photosynthetic pigment concentrations ($Chl$ $a$, $Chl$ $b$, and $Car$)
- Specific Leaf Weight (SLW)
- Leaf Dry Matter Content (LDMC)

These correlations suggest

关键词

Leaf Anatomical Structure and Photosynthetic Characteristics of Craigia yunnanensis Seedlings and Trees

Abstract: Craigia yunnanensis is a rare and endangered plant species listed under National Class I protection in China. To clarify the underlying causes of regeneration failure, particularly the challenges of sapling recruitment within natural populations, this study compared the photosynthetic characteristics, photosynthetic pigment contents, leaf epidermal traits, anatomical structures, and functional traits between seedlings and mature trees.

[TABLE:1]

Introduction

Craigia yunnanensis (Malvaceae) is a relict plant of the Tertiary period, possessing significant scientific value for studying the evolution and phytogeography of the Malvaceae family. Currently, the species is characterized by extremely small populations and a narrow distribution range, primarily restricted to limestone seasonal rainforests. Field observations indicate that while natural populations produce viable seeds, the transition from seedlings to saplings is severely hindered, leading to a bottleneck in population regeneration.

Understanding the physiological and anatomical adaptations of different life stages is crucial for developing effective conservation strategies. Photosynthesis is the fundamental physiological process driving plant growth and biomass accumulation, while leaf anatomical structures reflect the long-term adaptation of plants to their specific environmental conditions. By comparing these traits between seedlings and mature trees, we can identify the physiological constraints that limit the survival and development of Craigia yunnanensis in its natural habitat.

Materials and Methods

1.1 Study Site and Plant Materials

The study was conducted at the Guangxi Institute of Botany and the experimental forests of the Guangxi Zhuang Autonomous Region Academy of Forestry. Seedlings (2-3 years old) and mature trees (over 15 years old) were selected for comparative analysis. All samples were grown under similar edaphic conditions to minimize environmental variance.

1.2 Measurement of Photosynthetic Parameters

Gas exchange parameters, including the net photosynthetic rate ($P_n$), stomatal conductance ($G_s$), intercellular $CO_2$ concentration ($C_i$), and transpiration rate ($T_r$), were measured using a portable photosynthesis system (LI-6400XT). Measurements were taken on clear days between 09:00 and 11:00 AM on fully expanded, healthy leaves.

1.3 Determination of Photosynthetic Pigments

Chlorophyll a ($Chl_a$), chlorophyll b ($Chl_b$), and total chlorophyll ($Car$) were extracted using

seedlings (6-month-old) young trees (8-year-old) cultivated experimental plantation.

results

follows: maximum photosynthetic (12.00 light saturation point (LSP) young trees extremely significantly higher <0.01) those seedlings (5.69 respectively), whereas light compensation point (LCP) seedlings lower (11.37 indicating shade-tolerant strategy seedlings light-demanding strategy young trees.

Chlorophyll (Chl) carotenoid (Car) contents significantly higher young trees <0.05), their leaves thicker, developed palisade tissues, larger midrib vessel diameters, higher area, specific weight (SLW), matter content (LDMC).

Correlation

analysis

revealed significant highly significant positive correlations <0.05 <0.01) between thickness, chlorophyll content, LDMC. conclusion, seedlings adapt low-light understory environments, whereas young trees require higher light availability sustain their elevated photosynthetic capacity.

Insufficient understory light natural habitats likely hinders transition seedlings young trees, contributing species endangered status.

These findings provide essential scientific support for conservation and cultivation practices. It is recommended that thinning and canopy-opening measures be implemented to improve understory light conditions and promote population regeneration. Key words: Craigia yunnanensis; species with extremely small populations; photosynthetic characteristics; anatomy; chlorophyll.

Species with extremely small populations (PSESP) are a top priority for biodiversity conservation, as their survival status is directly linked to the integrity of ecosystems. Conducting conservation research on such species is of great strategic significance for preventing extinction and protecting China's unique biological genetic resources \cite{臧润国等，2016; 许玥等，2018}. Craigia yunnanensis, a typical PSESP, is not only listed as a national second-class key protected wild plant in China but is also assessed as an endangered species by the International Union for Conservation of Nature (IUCN) \cite{国家林业和草原局 农业农村部，2021}. This species is primarily distributed in the South Subtropical evergreen broad-leaved forest regions of Yunnan and Guizhou, commonly found in the lower parts of slopes, foot of mountains, and valley areas at altitudes of $800-1600$ m. C. yunnanensis is characterized by a straight and tall trunk with excellent processing performance, making it a precious timber species with significant economic value. Furthermore, the species exhibits a special adaptation to limestone karst habitats, making it an excellent candidate for ecological restoration in rocky desertification areas. As the type species of the genus Craigia, it occupies a critical position in plant phylogenetic research and possesses high scientific value.

Due to factors such as narrow distribution ranges, severe habitat fragmentation, and anthropogenic interference, the number of wild populations has continued to decrease, showing a clear declining trend. Field surveys indicate that existing populations are mostly scattered and discontinuous, with a widespread phenomenon of "regeneration gaps," suggesting serious obstacles in the natural regeneration process. This regeneration barrier not only directly threatens the sustainable survival of the population but also reflects potential key limiting factors within its life history. In-depth research into the physiological and ecological characteristics of C. yunnanensis seedlings and saplings, as well as the key factors influencing regeneration failure, is essential for formulating effective conservation strategies. Photosynthesis is the foundation of plant growth and development and serves as a vital physiological process; it is also a sensitive indicator of whether a plant is in its optimal growth environment and ecological condition \cite{Adamec, 1997}. Light conditions are also a critical environmental factor determining a plant's status within a community \cite{Zhang et al., 2017}. Photosynthetic capacity changes with tree age throughout the plant's life cycle \cite{Xiong et al., 2021}. Studying the differences in photosynthetic characteristics across different ages of endangered plants is of great significance for assessing and selecting suitable habitats. Many endangered tree species, such as Paranephelium hainanense and Vatica guangxiensis, exhibit significant differences between seedlings and adult trees in terms of photosynthetic capacity, light adaptation characteristics, and leaf structure. These differences often lead to varying demands for light environments at different developmental stages, thereby influencing their survival and growth within natural communities—particularly across the different light environments of the canopy and understory layers.

A comparative study of the photosynthetic physiological characteristics at different developmental stages not only helps to elucidate the mechanisms of endangerment but also provides an important foundation for implementing appropriate conservation measures.

Previous research on C. yunnanensis has primarily focused on potential suitable habitats, seed and fruit characteristics, seed germination, breeding systems and pollination, conservation genetics, and the complete chloroplast genome \cite{Wariss et al., 2017}. However, research in the field of photosynthetic physiological ecology remains a blank. Addressing the prominent issues in the population regeneration of C. yunnanensis, this study focuses on individuals introduced to the Guangxi Institute of Botany, Chinese Academy of Sciences. We explore the differences and relationships between the leaf photosynthetic characteristics and microscopic structures of seedlings and saplings. Specifically, this study aims to resolve the following questions: (1) What are the differences in the photosynthetic capacity of C. yunnanensis leaves between the seedling and sapling stages? (2) If differences in photosynthetic capacity exist, are they associated with leaf structure, chlorophyll content, or leaf phenotypic traits? The results of this study will provide a scientific basis for the conservation, introduction, and domestication of this endangered species.

1.1 研究地自然概况

The provenance of the species is located in Wenshan City, Yunnan Province, which is characterized by a south subtropical monsoon climate with an average annual temperature of 16–18°C. The soil in this region is primarily calcareous soil developed from limestone. The introduction site, located at the Guangxi Institute of Botany, falls within a central subtropical monsoon climate zone. In this area, the average temperature of the hottest month (July) is 28.3°C, while the average temperature of the coldest month (January) is 7.9°C. The annual relative humidity is 73%, with distinct wet and dry seasons and an annual sunshine duration of 1,550 hours. The soil at the introduction site consists of acidic soil developed from sandy shale and Quaternary red clay. Although there are certain differences in the natural environmental conditions between the two locations, Craigia yunnanensis continues to exhibit robust growth at the introduction site.

The C. yunnanensis seedlings used in this study were 6-month-old seedlings grown from seeds collected in 2021 from a wild population in Wenshan, Yunnan, and sown in Guilin. The saplings were 5-year-old plants introduced from Kunming, Yunnan, to the Guangxi Institute of Botany in 2017; their provenance also traces back to Wenshan, Yunnan. Basic information for both types of nursery stock is presented in [TABLE:1]. The seedlings were cultivated in an understory environment with a canopy light transmittance of 10%–15%, which simulates the understory light conditions where most natural seedling populations are found. The saplings were planted in a forest edge zone with a canopy light transmittance of 40%–60%, reflecting the light environment of the few natural populations that contain saplings. During the cultivation period, manual maintenance such as regular watering and weeding was performed. For this study, five healthy seedlings and five healthy saplings, all free of pests and diseases, were selected as experimental materials.

Growth period Average diameter Average height Average crown Seedling Young

1.3 方法

Measurement of various experimental indicators was conducted as follows. For seedlings, the $n$-th mature leaf growing downward from the top was selected. For young trees, the $n$-th mature leaf at the tip of sun-exposed branches in the middle of the canopy was selected for the measurement of photosynthetic parameters and subsequently tagged. Following these measurements, the corresponding leaves were collected for microscopic structural observation and determination of chlorophyll content. Each treatment was...

1.3.1 光合参数测定

Materials and Methods

Determination of Photosynthetic Light-Response Curves

The determination of light-response and photosynthetic response curves followed the methodologies described by Ye (2010) and Wang et al. (2014). Measurements were conducted using a Li-6400 portable photosynthesis system (Li-Cor, USA) on clear days between 09:00 and 12:00. Prior to measurement, the target leaves were subjected to light induction, with induction intensities set specifically for seedlings and saplings. An open gas circuit was maintained during the measurement process, with an air flow rate of $500\ \mu\text{mol}\cdot\text{s}^{-1}$ and a leaf chamber temperature of $25^\circ\text{C}$.

The light intensity gradients for the light-response curves were set sequentially at $2000, 1800, 1600, 1400, 1200, 1000, 800, 600, 400, 200, 150, 100, 50, 25, 0\ \mu\text{mol}\cdot\text{m}^{-2}\cdot\text{s}^{-1}$. The $CO_2$ concentration gradient was maintained at $400\ \mu\text{mol}\cdot\text{mol}^{-1}$. The net photosynthetic rate ($P_n$) was recorded after a balance time of 120–180 seconds at each gradient. Based on the measurement results, a modified rectangular hyperbolic model was used to fit the light-response curves and calculate relevant photosynthetic parameters. Simultaneously, stomatal conductance ($G_s$), transpiration rate ($T_r$), and water use efficiency ($WUE = P_n/T_r$) were recorded.

Determination of Photosynthetic Pigment Content

The contents of chlorophyll a, chlorophyll b, total chlorophyll, and carotenoids were determined according to the method described by Li (2000). Leaf samples used for photosynthetic measurements were collected, and $0.1\text{ g}$ samples were obtained using a puncher. Pigments were extracted using 95% ethanol in the dark. The absorbance at $665\text{ nm}$, $649\text{ nm}$, and $470\text{ nm}$ was measured using a Perkin Elmer UV-Vis spectrophotometer. These values were used to calculate the concentration of each pigment and the chlorophyll a/b ratio.

Observation of Leaf Microstructure

Leaf epidermal characteristics were observed following standard electron microscopy preparation methods. After sampling, specimens underwent fixation, dehydration, drying, and gold sputtering. Observations were performed using a ZEISS EVO18 scanning electron microscope. Stomatal morphological parameters were measured using the Vision image analysis system.

For leaf anatomical structure, the modified paraffin section method was employed. Following sectioning and staining, imaging was performed using an automated digital slide scanning system. Leaf thickness, upper and lower epidermal thickness ($T_{up}$ and $T_{low}$), and mesophyll tissue thickness were measured using CaseViewer software. Each sample was measured across 30 replicates to ensure statistical accuracy.

Measurement of Leaf Phenotypic Traits

Ten healthy, disease-free, fully expanded leaves with consistent light exposure were selected from each plant. Leaf length and width were measured using a digital caliper (Germany). Leaf area was determined using a Li-3000 area meter (Li-Cor, USA). After measuring the fresh weight, leaves were oven-dried to a constant weight to determine the dry weight. These measurements were used to calculate the specific leaf weight ($SLW$) and leaf dry matter content ($LDMC$).

Data Analysis

Data statistical analysis and graphing were performed using Microsoft Excel and Origin software. Photosynthetic parameters were fitted using the modified rectangular hyperbolic model in the Photosynthesis Calculation 4.0 software. Statistical processing was conducted using SPSS software, where $P < 0.05$ indicated significant differences, $P < 0.01$ indicated highly significant differences, and $P > 0.05$ indicated no significant difference. Correlation analyses were performed between leaf structural characteristics, chlorophyll content, leaf phenotypic traits, and photosynthetic parameters. All experimental data are presented as mean values.

2.1 滇桐幼苗和

The response of gas exchange parameters in Craigia yunnanensis seedlings and young trees to light intensity increased with rising photosynthetic photon flux density (PPFD). Within the range of 0–100 $\mu\text{mol}\cdot\text{m}^{-2}\cdot\text{s}^{-1}$, these parameters exhibited a linear increase, followed by a slower rise until reaching the light saturation point ($LSP$), after which they tended to stabilize. The overall trends for seedlings and young trees were largely identical. Specifically, the net photosynthetic rate ($P_n$), transpiration rate ($T_r$), and water-use efficiency ($WUE$) all increased with rising light intensity. However, the stomatal conductance ($G_s$) eventually decreased after reaching its peak at a specific light intensity (Figure [FIGURE:1]).

Within this range, the responses of leaf net photosynthetic rate ($P_n$), stomatal conductance ($G_s$), transpiration rate ($T_r$), and water-use efficiency ($WUE$) of C. yunnanensis seedlings and young trees to light intensity were observed.

2.1.2 滇桐幼苗和

Light-Response Parameters

The results for light-response parameters indicate that Craigia yunnanensis seedlings and young trees exhibit significant differences in their photosynthetic performance. Specifically, the maximum net photosynthetic rate ($P_{max}$) of young trees was significantly higher than that of seedlings, showing an increase of 110.9%. The light compensation point (LCP) and light saturation point (LSP) of young trees also increased significantly by 36.5% and 62.0%, respectively. Furthermore, the apparent quantum efficiency (AQE) of young trees was 24.7% higher than that of seedlings, while the dark respiration rate ($R_d$) also showed a significant increase of 12.1%.

[TABLE:1] Parameters of photosynthetic light-response curves in leaves of Craigia yunnanensis seedlings and young trees.

Significance Testing

Note: ** indicates an extremely significant difference ($P < 0.01$); * indicates a significant difference ($P < 0.05$); and "ns" indicates no significant difference ($P > 0.05$).

significant difference ( $P \ge 0.05$) . T he same below.

2.1.3 滇桐幼苗和幼树的光合

Response of Net Photosynthetic Rate to $CO_2$ Concentration in Leaves of Parashorea chinensis Seedlings and Young Trees

The net photosynthetic rate ($P_n$) of both seedlings and young trees increases with rising $CO_2$ concentrations before gradually reaching a stable state. Under identical environmental conditions, the $P_n$ of young trees is higher than that of seedlings. This difference is particularly pronounced during the $CO_2$ saturation stage ($C_a > 800 \mu mol \cdot mol^{-1}$), where the net photosynthetic rate of young trees is approximately 1.5 times that of seedlings.

2.1.4 滇桐幼苗和幼树的光合

Compared to seedlings, the potential maximum net photosynthetic rate ($P_{nmax}$) of saplings significantly increased by 49.6% and 10.1%, respectively. Simultaneously, the initial carboxylation efficiency ($CE$) and photorespiration rate ($R_p$) of saplings were significantly higher than those of seedlings, showing increases of 121.7% and 88.9%, respectively. In contrast, no significant difference was observed between seedlings and saplings regarding [missing parameter].

[TABLE:1] Photosynthetic response parameters of Craigia yunnanensis leaves in seedlings and saplings. ($P_{nmax}$: potential maximum net photosynthetic rate; $CE$: initial carboxylation efficiency; $R_p$: photorespiration rate; Growth period).

Seedling Young

Significance Testing

In the field of scientific research and statistical analysis, significance testing (also known as hypothesis testing) serves as a fundamental framework for determining whether an observed effect or relationship in a dataset is likely due to a specific cause or merely the result of random chance. By quantifying the probability of obtaining the observed results under a specific set of assumptions, researchers can make informed decisions about the validity of their experimental hypotheses.

The Core Logic of Hypothesis Testing

The process of significance testing typically begins with the formulation of two opposing hypotheses: the null hypothesis ($H_0$) and the alternative hypothesis ($H_1$ or $H_a$). The null hypothesis generally represents a state of "no effect" or "no difference," while the alternative hypothesis represents the effect the researcher hopes to demonstrate.

To evaluate these hypotheses, a test statistic is calculated from the sample data. This statistic follows a known probability distribution (such as the $t$-distribution, $Z$-distribution, or $F$-distribution) under the assumption that $H_0$ is true. The final decision is based on the $p$-value, which represents the probability of observing a test statistic as extreme as, or more extreme than, the one actually obtained, assuming the null hypothesis is correct.

Significance Levels and the $p$-value

The significance level, denoted by $\alpha$, is a threshold pre-defined by the researcher (commonly set at $0.05$, $0.01$, or $0.10$). It represents the maximum risk the researcher is willing to take of committing a Type I error—rejecting a true null hypothesis (a "false positive").

• If $p \le \alpha$: The result is considered "statistically significant." The researcher rejects $H_0$ in favor of $H_1$, concluding that the observed effect is unlikely to have occurred by chance alone.
• If $p > \alpha$: The researcher fails to reject $H_0$. This does not necessarily prove that the null hypothesis is true, but rather indicates that there is insufficient evidence to support the alternative hypothesis at the chosen significance level.

Common Statistical Tests

The choice of a significance test depends on the nature of the data (categorical vs. continuous), the sample size, and the underlying distribution. Some of the most widely used tests include:

1. t-tests: Used to compare the means of two groups (e.g., Independent Samples $t$-test

2.2 滇桐幼苗和幼树的光合色素含量

There were significant differences in the photosynthetic pigment content between seedlings and saplings. Specifically, total chlorophyll content increased by 48.7% to 56.5% during development; however, carotenoid content (45.2%) showed no significant difference across the different growth stages.

Photosynthetic pigment content relative proportions leaves Craigia yunnanensis seedlings young trees

2.3 滇桐幼苗和幼树的叶片显微结构

Leaf epidermal characteristics: Observations of the upper and lower epidermis of seedling and young tree leaves (Figure [FIGURE:1]) reveal that stomata are distributed exclusively on the lower epidermis. In contrast, epidermal hairs are present on both the upper and lower surfaces. While there were no significant differences in the longitudinal axis or the total area of the stomata between the two growth stages, the stomatal density of the young trees was significantly higher than that of the seedlings.

[FIGURE:1] Upper epidermis, lower epidermis, and stomata of seedlings; upper epidermis, lower epidermis, and stomata of young trees. Epidermal characteristics of Craigia yunnanensis seedlings and young trees. [TABLE:1] Characteristics of stomatal development in the leaves of Craigia yunnanensis seedlings and young trees. Vertical stomatal length, transverse stomatal width, and growth period (Seedling vs. Young tree).

Significance test

2.3.2 滇桐幼苗和幼树的叶片解剖结构特征

The leaf anatomical structures of both seedlings and young trees exhibit distinct structural stratification. These anatomical structures primarily consist of fundamental tissue layers, including the upper epidermis, palisade tissue, spongy tissue, and the lower epidermis. Compared to seedlings, the leaves of young trees showed a highly significant increase in total leaf thickness by 31.2%. Specifically, the thickness of the upper and lower epidermis increased significantly by 11.2% and 42.9%, respectively. Furthermore, the thickness of the palisade tissue and spongy tissue increased significantly by 46.2% and 34.7%, respectively, while the midrib vessel diameter increased significantly by 44.5%. However, the ratio of palisade tissue thickness to spongy tissue thickness (PTT/STT) did not reach a level of statistical significance between seedlings and young trees.

[FIGURE:1] Transverse sections of seedling leaves and midribs; Transverse sections of young tree leaves and midribs. PT: Palisade tissue; ST: Spongy tissue; VC: Vascular cambium. Transverse sections of leaves and midribs in seedlings and young trees. UE: Upper epidermal; PT: Palisade tissue; ST: Spongy tissue; LE: Lower epidermal; X: Xylem; P: Phloem; VC: Vascular cambium. Anatomical structure of Taiwania yunnanensis seedlings and young trees. LE: Lower epidermal cells; PT: Palisade tissue thickness; ST: Spongy tissue thickness; MD: Midrib vessel diameter. Growth period: Seedling, Young tree.

Significance test

2.4 滇桐幼苗和幼树的叶片表型性状

There are highly significant differences in the leaf phenotypic traits between seedlings and young trees of Craigia yunnanensis. The leaf length of young trees is significantly greater than that of seedlings, with an increase of 31.2%. The most pronounced difference was observed in [specific trait], which increased significantly by 58.0%, while [another trait] in young trees showed a highly significant increase of 431.7%. Regarding leaf structural traits, the specific leaf weight (SLW) of young trees increased significantly by 256.8%, and the leaf dry matter content (LDMC) also showed a highly significant increase.

Specific; Leaf dry matter content; Growth period; Length; Width; Seedling; Young tree

Significance test

2.5 滇桐叶片显微结构特征、叶绿素含量、叶片表型性状与光合特征参数的相关性

The leaf thickness and midrib vessel diameter of Craigia yunnanensis exhibited significant or highly significant positive correlations with the maximum net photosynthetic rate ($P_{n,max}$) and the light compensation point ($LCP$), while showing a highly significant negative correlation with the apparent quantum efficiency ($AQE$). Total chlorophyll content was highly significantly positively correlated with $P_{n,max}$ and highly significantly negatively correlated with $AQE$. Furthermore, leaf area ($LA$), specific leaf weight ($SLW$), and leaf dry matter content ($LDMC$) showed significant or highly significant positive correlations with $P_{n,max}$ and a significant negative correlation with $AQE$.

** denotes highly significant correlation ($P < 0.01$); * denotes significant correlation ($P < 0.05$). MVD: midrib vessel diameter; Chl: total chlorophyll content; LDMC: leaf dry matter content; $P_{n,max}$: maximum net photosynthetic rate; $LSP$: light saturation point; $LCP$: light compensation point; $AQE$: apparent quantum efficiency.

indicates extremely significant correlation 0.001); indicates significant correlation 0.01); indicated significant correlation 0.05). thickness; Median catheter diameter; Total chlorophyll; area; Specific area; Specific weight; matter content; Maximum photosynthetic rate; Light saturation point; Light compensation point; Apparent quantum efficiency.

Correlation Between Chlorophyll Content, Leaf Phenotypic Traits, and Photosynthetic Characteristic Parameters in Rauvolfia yunnanensis Seedlings and Young Trees

Abstract

This study investigates the physiological and morphological characteristics of Rauvolfia yunnanensis, a medicinal plant species. By analyzing the correlation between chlorophyll content, leaf phenotypic traits, and photosynthetic parameters, we aim to elucidate the growth mechanisms and environmental adaptation strategies of this species during its early developmental stages. Our findings provide a theoretical basis for the cultivation and resource management of R. yunnanensis.

1. Introduction

Rauvolfia yunnanensis Tsiang is a significant medicinal plant belonging to the Apocynaceae family, primarily distributed in the Yunnan province of China. It is rich in indole alkaloids, which are widely used in the treatment of hypertension and cardiac arrhythmias. Despite its medicinal importance, the physiological processes governing its growth—particularly the relationship between leaf morphology and photosynthetic efficiency—remain insufficiently understood.

Photosynthesis is the fundamental process driving plant biomass accumulation. It is influenced by both internal factors, such as chlorophyll content and leaf structure, and external environmental conditions. Understanding how leaf phenotypic traits (such as leaf area and specific leaf weight) correlate with photosynthetic parameters (such as net photosynthetic rate, stomatal conductance, and transpiration rate) is crucial for optimizing the cultivation of R. yunnanensis seedlings and young trees.

2. Materials and Methods

2.1 Experimental Materials

The study was conducted using healthy R. yunnanensis seedlings (1-year-old) and young trees (3-year-old) grown under controlled nursery conditions.

2.2 Measurement of Leaf Phenotypic Traits

Leaf length, width, and area were measured using a digital leaf area meter. Specific leaf weight (SLW) was calculated as the ratio of leaf dry mass to leaf area.

2.3 Determination of Chlorophyll Content

Chlorophyll a ($Chl_a$), chlorophyll b ($Chl_b$), and total chlorophyll ($Chl_{total}$) concentrations were determined using the ethanol extraction method. Absorbance was measured at 663 nm and 645 nm using a spectrophotometer, and concentrations were calculated using standard equations:
$$Chl_a = 12.7 \cdot A_{663} - 2.69 \cdot A_{645}$$
$$Chl_b = 22.9 \cdot A_{645} - 4.68 \cdot A_{663}$$

3.1 光合

This study comprehensively compares the photosynthetic differences between the seedling and sapling stages of Craigia yunnanensis, systematically revealing the photosynthetic adaptation strategies that shift across developmental stages. The transition of C. yunnanensis from seedling to sapling is accompanied by a profound transformation of the photosynthetic system, moving from a conservative shade-tolerant strategy to an active high-light investment strategy. Compared to the trends observed in species such as Vatica guangxiensis and Larix gmelinii, where photosynthetic capacity steadily increases with development \cite{LuoQihui, PanXinfengEtAl}, the saplings of C. yunnanensis exhibit particularly significant increases in key parameters such as $P_n$, $G_s$, and $T_r$. This may stem from unique mechanisms involving the reconstruction of photosynthetic apparatus and the optimization of carbon assimilation pathways. The internal driving force behind this leap in photosynthetic capacity lies in the co-evolution of leaf structural traits and photosynthetic functions. Correlation analysis indicates that $P_n$ is significantly positively correlated with $LT$ and $VD$. An increase in leaf thickness ($LT$) is typically accompanied by the development of palisade tissue, which accommodates more chloroplasts and enhances light energy capture capacity \cite{LengHanbing}. Meanwhile, the enlargement of midrib vessel diameter ($VD$) directly improves water transport efficiency, effectively alleviating stomatal limitations on photosynthesis and providing a structural foundation for high net photosynthetic rates. Compared to species like Ulmus szechuanica, the higher $P_n$ and $LSP$ exhibited by C. yunnanensis saplings suggest a specialized adaptation and carbon acquisition advantage in high-intensity light environments. This is not merely a quantitative increase but a physiological hallmark of its successful niche transition from the low-light understory to high-light environments such as forest gaps or the canopy. The low $P_n$ of C. yunnanensis seedlings is not an optimized strategy for adapting to shaded environments; rather, it is likely a manifestation of incomplete development of the photosynthetic apparatus and restricted $RuBP$ carboxylase activity under the integrated environmental stresses of the understory. Combined with a lower dark respiration rate ($R_d$), this low-activity photosynthetic state leads directly to the slow accumulation of carbon assimilation products. Consequently, seedlings lack sufficient material and energy support during the transition from low-light understory conditions to high-light environments. Insufficient carbon acquisition capacity at the seedling stage likely constitutes a critical physiological bottleneck in the transition from seedlings to saplings during natural population regeneration.

Based on the aforementioned differences in stage-specific strategies, light environment management in conservation and cultivation must be precise. It is recommended to implement stage-specific light management strategies. During the seedling stage (1–3 years), a relative light intensity of 10%–20% should be maintained; moderate shade can be created through understory planting or shade nets to ensure survival and initial establishment. Upon entering the sapling transition phase, light levels should be gradually increased through artificial thinning. It is suggested to thin surrounding competing trees in stages before the spring growing season, gradually increasing the light transmittance to approximately 50% to promote the development of photosynthetic apparatus and carbon accumulation. The intensity of thinning should follow a gradient to avoid photosynthetic system stress caused by abrupt environmental changes. Future research could further integrate photosynthetic enzyme activity, mesophyll conductance, and molecular regulatory mechanisms to deeply analyze the physiological and genetic basis of photosynthetic development in C. yunnanensis. Photosynthesis in plants is an extremely complex process. The differences in photosynthetic characteristics of woody plants are part of the interaction between various physiological and ecological processes and adaptation mechanisms, which are influenced by numerous factors including physiology and biochemistry. To fully understand these differences, it is necessary to conduct correlation analyses on physiological and biochemical indicators.

3.2 光合色素

The content and ratio of photosynthetic pigments directly reflect the investment trade-offs plants make between light energy capture and consumption. The chlorophyll and carotenoid contents of saplings were significantly higher than those of seedlings.

There was a highly significant positive correlation, a finding that contradicts the common strategy observed in many plants of increasing pigment content to enhance light-harvesting capacity under low-light conditions \cite{郑元超}. This phenomenon suggests that Craigia yunnanensis seedlings adopt a risk-aversion-centered conservative strategy within the fluctuating understory light environment. Their lower pigment content results from a trade-off against the risk of photodamage; the core of this strategy lies in improving the utilization efficiency of existing pigments rather than engaging in blind resource expansion. This aligns with the discussion by Sun Xiaoling et al. \cite{孙小玲等}, which notes that plants under shaded conditions adjust their photosystem ratios and antenna pigment complex structures to achieve efficient light energy conversion and dissipation. In contrast, saplings in stable high-light environments tend to increase the scale of their pigment investment. This not only provides a foundation for high carbon assimilation but also gives the increase in carotenoid content a dual significance: on one hand, they act as accessory photosynthetic pigments to broaden the light absorption spectrum; on the other hand, they serve the critical function of enhancing photoprotective mechanisms \cite{王博轶和冯玉龙}. This shift in pigment allocation strategy represents a precise, differentiated adaptation by C. yunnanensis to the heterogeneous light environments encountered at different developmental stages. This adaptive process likely involves multi-level physiological remodeling—ranging from photosynthetic pigment synthesis and photosystem structural adjustments to the regulation of energy metabolism—and is the result of long-term interaction and co-evolution between its growth and development strategies and the light resource conditions of its habitat.

3.3 叶片显微结构与功能性状

The leaves of Craigia yunnanensis exhibit strong structural support for its ecological strategies at the anatomical level. Its leaves are typically bifacial, with stomata distributed exclusively on the lower epidermis. This structural adaptation effectively reduces unnecessary transpiration caused by direct sunlight on the upper epidermis, aligning with the typical adaptive characteristics of many heliophilous (light-demanding) tree species to high-light environments. More importantly, compared to seedlings, the stomata of saplings exhibit typical "high density and small size" characteristics. The advantage of this structural combination lies in granting the stomatal population more sensitive regulatory capabilities: high stomatal density ensures efficient gas exchange, while the small aperture allows each stomatal unit to achieve faster opening and closing responses. Research indicates that this stomatal configuration enables plants to achieve a finer dynamic balance between water-use efficiency and carbon assimilation, making it particularly suitable for habitats with fluctuating light intensities, such as forest gaps \cite{REF_1}. Regarding leaf anatomical structure, the development of palisade tissue is especially significant during the transition from seedling to sapling. The palisade tissue not only increases in thickness, but its cells also become more elongated and are arranged more densely and orderly. This structural change not only increases the chloroplast capacity per unit leaf area but, more importantly, optimizes the distribution path of light energy within the mesophyll tissue, thereby enhancing light-use efficiency. Furthermore, the arrangement pattern of spongy tissue cells also changes, with more developed intercellular spaces that may facilitate $CO_2$ diffusion among mesophyll cells, indirectly supporting higher photosynthetic rates.

From the seedling to the sapling stage, key functional traits—including leaf area ($LA$), leaf thickness ($LT$), specific leaf weight ($SLW$), and leaf dry matter content ($LDMC$)—exhibit a significant and synergistic increase. The coordinated enhancement of these traits is not an isolated phenomenon but collectively points toward a more robust resource-acquisition strategy. A larger leaf area directly expands the light-receptive surface for photosynthesis. Thicker leaves and higher specific leaf weight typically signify more developed palisade tissue, with more cell layers and denser arrangements; this directly leads to an increased density of photosynthetic apparatus per unit leaf area, laying a solid foundation for high photosynthetic rates \cite{REF_2}. Meanwhile, a higher dry matter content ($LDMC$) further reflects a greater proportion of investment in structural materials within the leaf. This investment not only strengthens the mechanical support of the leaf to withstand physical stresses such as stronger winds but also extends the functional lifespan of the leaf, which is a prerequisite for long-term efficient carbon accumulation \cite{Wang_et_al_2021}. The synergistic transformation of these microstructures and functional traits constitutes the structural basis for the transition of Craigia yunnanensis from a "survival-oriented" to a "growth-oriented" strategy. Compared to species such as Vatica guangxiensis and Larix gmelinii, the transformation in the leaf structure of Craigia yunnanensis is more pronounced. This may be related to its specific ecological niche and evolutionary history. These profound structural changes not only support the enhancement of its photosynthetic capacity but also reflect the precise regulation of environmental adaptation strategies during the plant's ontogeny.

4 结论

This research systematically reveals the photosynthetic characteristics and structural adaptations of Craigia yunnanensis during its seedling and sapling stages, which together constitute a light adaptation strategy that shifts across developmental phases. Saplings exhibit typical characteristics of heliophilous (light-demanding) species, showing significant increases in maximum net photosynthetic rate ($P_{nmax}$), light saturation point ($LSP$), and water-use efficiency ($WUE$). These physiological improvements are accompanied by optimized leaf anatomical structures—such as enlarged midrib vessels—and adjusted dry matter allocation strategies, including increased specific leaf weight ($SLW$) and leaf dry matter content ($LDMC$). These traits demonstrate a strong adaptability and carbon assimilation advantage in high-intensity light environments.

In contrast, while seedlings possess a degree of shade tolerance (indicated by a lower light compensation point), their photosynthetic pigment content remains low and their photosynthetic apparatus is incompletely developed, leading to limited light-energy utilization efficiency. Rather than following common low-light adaptation strategies, such as increasing pigment investment, seedlings appear to maintain low pigment levels and conservative resource allocation to avoid the risk of photoinhibition caused by sudden intense light in forest gap environments.

The limitation of carbon accumulation caused by insufficient light in natural understory environments represents a critical physiological bottleneck hindering the transition of Craigia yunnanensis from the seedling to the sapling stage. This may be a fundamental internal factor contributing to obstructed population regeneration and the species' endangered status. In conservation and cultivation practices, management should align with the ecological requirements of each developmental stage: maintaining moderate shade (approximately 25%–50% light transmittance) during the seedling stage to ensure survival and establishment, while implementing progressive thinning during the sapling transition to gradually increase light intensity. Such measures will promote the development of the photosynthetic apparatus and carbon accumulation, providing a physiological and ecological basis for the restoration of this endangered population.

参考文献

ADAMEC Photosynthetic characteristics aquatic carnivorous plant Aldrovanda vesiculosa Aquatic Botany ZHENG Photosynthetic induction seedlings tropical rainforest species Phytoecologica Sinica, 27(5):

Study on photosynthetic induction of woody plant seedlings in a tropical rainforest. Chinese Journal of Plant Ecology, 27(5): 623.] Effects of light intensities on morphological structure, stoichiometry, and non-structural carbohydrates of Magnolia sinostellata seedlings. Chinese Journal of Ecology, 42(6):

Effects of light intensity on leaf morphological structure, stoichiometric characteristics, and non-structural carbohydrates of Magnolia sinostellata seedlings. Chinese Journal of Ecology, 42(6): 1315.]

Analysis

Characteristics Germination Difference Endangered Plant Craigia yunnanensis Guizhou Forestry Science Technology, 49(1):

Analysis of Seed and Fruit Characteristics and Differences in Seed Germination of the Endangered Plant Craigia yunnanensis. Guizhou Forestry Science and Technology, 49(1). CHENG et al. Stomatal morphological characteristics and their effects on transpiration for two species in the Maolan Karst of Guizhou Province. Journal of Nanjing Forestry University (Natural Sciences Edition), 45(5).

Leaf stomatal morphological characteristics and their influence on transpiration of two tree species in the Maolan Karst forest, Guizhou. Journal of Nanjing Forestry University (Natural Sciences Edition), 45(5): 132. Advances in the Study of Photoprotection in Plant Photosynthesis. Biotechnology Bulletin, 41(10).

Research progress on the photoprotection mechanisms of plant photosynthesis. Biotechnology Bulletin, 41(10). Photosynthetic eco-physiological adaptability of the endangered plant Tetracentron sinense across different habitats and altitudes [J].

Biologia plantarum, CHENG Photosynthetic Characteristics Antioxidant

Enzyme Activity Sophora japonica Different Journal Northwest Forestry University, 33(3):

Comparative Study on Photosynthetic Characteristics and Antioxidant Enzyme Activities of Sophora japonica at Different Ages. Journal of Northwest Forestry University, 33(3). Research Progress on the Impact of Photosynthetic Product Allocation on Plant Growth [J/OL].

Journal of Temperate Forestry Research. Research Progress on the Impact of Plant Photosynthetic Product Allocation on Growth [J/OL].

ZHANG Regulation Carotenoids Biosynthesis Horticultural Crops Horticulturae Sinica, 42(9):

Research progress on carotenoid synthesis and regulation in horticultural plants. Chinese Journal of Applied Ecology, 42(9): 1648.] ZHANG, L. Pollination biology and breeding system of Craigia yunnanensis in fragmented habitats. Chinese Journal of Ecology, 31(9):

Pollination biology and breeding system of Craigia yunnanensis in fragmented habitats. 31(9): 2217-2224.] Hydraulic architecture characteristics and drought adaptation strategies of three Caragana species. Acta Ecologica Sinica, 38(14):

Hydraulic architecture characteristics and drought adaptation of three Caragana species. 38(14): 4993.] ZHANG, Y. Endangered plants of Yunnan, China. Kunming:

Yunnan Science and Technology Press: Rare and Endangered Plants of Yunnan, China. Kunming: Yunnan Science and Technology Press, 146.] Effects of simulated forest gaps on Phoebe bournei saplings. Changsha:

Central South University of Forestry and Technology. Study on the effects of simulated forest gaps on Phoebe bournei saplings and soil. [Master's thesis, Central South University of Forestry and Technology]. Changes in photosynthesis characteristics and chlorophyll fluorescence of Paranephelium hainanensis, a species with an extremely small population. Chinese Journal of Ecology, 39(1):

Dynamic changes in photosynthetic characteristics and chlorophyll fluorescence parameters of leaves in the extremely small population species Paranephelium hainanensis. 39(1): 102-110. Effects of shading on photosynthetic characteristics and leaf anatomical structure of Ulmus szechuanica seedlings. Acta Botanica Boreali-Occidentalia Sinica, 43(6): 1006-1016. [Effects of shading on photosynthesis and leaf anatomical structure of Ulmus szechuanica seedlings. Acta Botanica Boreali-Occidentalia Sinica, 43(6): 1006-1016.] Effects of light environments within the Cinnamomum camphora canopy on functional traits and photosynthetic characteristics.

Chinese Journal of Applied Ecology, 34(8): Effects of light environment on leaf functional traits and photosynthetic characteristics. Journal of Applied Ecology, 34(8): 2122.] Principles and techniques of plant physiological and biochemical experiments. Beijing:

Higher Education Press. Principles and techniques of plant physiological and biochemical experiments. Beijing: Higher Education Press. Study on the acclimation of seedling and sapling foliage of Taxus cuspidata to different light intensities. Harbin: Northeast Forestry University.

Study on the photosynthetic physiological adaptability of Taxus cuspidata saplings and seedlings. Harbin: Northeast Forestry University.

Influence of drought stress on growth, gas exchange, and chlorophyll fluorescence of two varieties of Vernicia fordii seedlings. Acta Ecologica Sinica, 37(5): 1515-1524. [Effects of drought stress on growth, gas exchange, and chlorophyll fluorescence parameters of two Vernicia fordii seedlings. 37(5): 1524.] Leaf angle change and anatomical structure of Populus deltoides, Populus cathayana, and their hybrids. Journal of Beijing Forestry University, 40(2):

Leaf angle changes and anatomical structures of Populus deltoides, Populus cathayana, and their hybrid offspring. Journal of Beijing Forestry University, 40(2): Changes in photosynthesis of Torreya grandis 'Merrillii' leaves in different months and at different tree ages. Journal of Zhejiang A&F University, 39(1):

Photosynthetic characteristics of Torreya grandis leaves in different months and at different tree ages. Journal of Zhejiang A&F University, 39(1): Effects of light intensity on photosynthetic characteristics of the endangered species Ulmus elongata. Chinese Journal of Ecology, 40(4):

Effects of light intensity on the photosynthetic characteristics of the endangered plant Ulmus elongata. Chinese Journal of Ecology, 40(4): 980-988.] Effects of shading on photosynthetic characteristics of Larix gmelinii seedlings and saplings. Hohhot:

Inner Mongolia Agricultural University. Effects of shading on the photosynthetic characteristics of Larix gmelinii seedlings and saplings. Hohhot: Inner Mongolia Agricultural University. National Forestry and Grassland Administration & Ministry of Agriculture and Rural Affairs (2021).

List of National Key Protected Wild Plants [EB/OL]. (2021-09-08). National Forestry and Grassland Administration and Ministry of Agriculture and Rural Affairs. JIANG, Y. Comparison of photosynthesis and leaf structure between seedlings and adult plants of Manglietia aromatica [J/OL].

Molecular Plant Breeding. Comparison of leaf photosynthesis and structure between seedlings and adult plants of the endangered species Manglietia aromatica [J/OL].

Molecular Plant Breeding, 1-11.] How stomatal configuration and photosynthetic traits jointly affect water-use efficiency in forests along climate gradients. New Phytologist, 244(4):

Comparative study photosynthetic characteristics microstructure Vatica guangxiensis seedling adult Guihaia, 45(1):

Comparative Study on Photosynthetic Characteristics and Leaf Microstructure of Vatica mangachapoi Seedlings and Adult Trees. Journal of Tropical and Subtropical Botany, 45(1): 133-146.] Response of Anatomical Structure and Photosynthetic Characteristics of Capsicum Seedling Leaves to Low Light. Acta Horticulturae Sinica, 36(2):

Response of anatomical features and photosynthetic characteristics of pepper (Capsicum annuum L.) seedling leaves to low light intensity. Acta Horticulturae Sinica, 36(2): 208.] A review of the acclimation of photosynthetic pigment composition in plant leaves to shaded environments. Chinese Journal of Plant Ecology, 34(8):

Acclimation of photosynthetic pigment composition in plant leaves to shading. Chinese Journal of Plant Ecology, 34(8): 999.] MICHAEL, LAURENCE. Tiliaceae [M].

Flora China. Beijing: Science

Press: Effects growth light intensities photosynthesis seedlings tropical forest species Ecologica Sinica, 25(1):

Research Progress on Light Response Models of Plant Electron Transport Rates

Introduction

The light response of photosynthesis is a fundamental process in plant physiology, reflecting how plants capture and utilize light energy under varying environmental conditions. While traditional research has focused extensively on the response of the net photosynthetic rate ($P_n$) to light intensity, the underlying electron transport rate (ETR) provides a more direct representation of the photochemical efficiency of Photosystem II (PSII). Understanding the relationship between light intensity and the electron transport rate is crucial for evaluating plant stress responses, photosynthetic capacity, and overall productivity.

1. The Significance of Electron Transport Rate (ETR)

The electron transport rate serves as a vital bridge between the absorption of light energy and the chemical fixation of carbon. Unlike gas exchange measurements, which can be influenced by stomatal conductance and respiration, ETR measurements—often derived from chlorophyll fluorescence—offer a non-destructive insight into the actual efficiency of the photosynthetic apparatus. By modeling the light response of ETR, researchers can quantify key parameters such as the maximum electron transport rate ($J_{max}$), the initial quantum yield of electron transport ($\alpha$), and the light saturation point ($I_{sat}$).

2. Evolution of Light Response Models

Historically, models used to describe the light response of $P_n$ have been adapted for ETR. These include the rectangular hyperbola model, the non-rectangular hyperbola model, and the exponential model. However, these classical models often fail to account for the phenomenon of "photoinhibition," where the electron transport rate declines at supra-optimal light intensities.

Recent advancements have led to the development of modified models, such as the modified rectangular hyperbola model. This model introduces a photoinhibition term, allowing for a more accurate fit of ETR data across a wider range of light intensities, including those that induce photosynthetic stress. These mathematical refinements enable a more precise estimation of the light compensation point ($I_c$) and the dynamic changes in photochemical efficiency.

[FIGURE:1]

3. Factors Influencing ETR Light Response

The light response of ETR is not static; it is highly plastic and influenced by the growth environment. Research on tropical rainforest tree species has demonstrated that seedlings grown under different light regimes (e.g., gap light vs. understory shade) exhibit distinct ETR strategies.

• Light Intensity: Seedlings adapted to high-light environments typically exhibit higher $J_{max}$ and $I$

Spatial variations adaptive mechanisms plant stomatal traits Inner Mongolian Plateau Ecologica Sinica, 43(9):

Spatial Variation of Plant Stomatal Traits and Their Adaptation Mechanisms on the Inner Mongolian Plateau. Chinese Journal of Ecology, 43(9): 3777. Photosynthetic characteristics of Sinojackia huangmeiensis, a species with an extremely small population. Chinese Journal of Ecology, 43(3).

Ecophysiological characteristics of photosynthesis in Sinojackia huangmeiensis, a wild plant with an extremely small population. Chinese Journal of Ecology, 43(3). WARISS: The complete chloroplast genome of Craigia yunnanensis, an endangered plant species with extremely small populations (PSESP) in South China.

Mitochon 4(2): Potential Suitable Relic Plant Craigia yunnanensis Yunnan Province Journal China Forestry Science, 53(2):

Research on the potential suitable distribution areas of the relict plant Craigia yunnanensis in Yunnan Province. Theoretical and practical research on the conservation of Plant Species with Extremely Small Populations in China. Biodiversity Science, 30(10).

Research progress on the theory and practice of protecting wild plants with extremely small populations in China. Biodiversity Science, 30(10). Classification and species composition characteristics of the living communities of Craigia yunnanensis (Tiliaceae), a second-class national protected plant. Guizhou Science, 40(3).

Classification and species composition characteristics of the survival communities of the protected plant Craigia yunnanensis. Guizhou Science, 40(3): 11-17. A review of modeling responses of photosynthesis to light. Chinese Journal of Plant Ecology, 34(6).

Investigation of the light-response model of photosynthesis. Chinese Journal of Plant Ecology. Construction of a response model for plant stomatal conductance. Chinese Journal of Plant Ecology, 45(4).

ZHANG Endemic genera plants China Beijing: Science Press:

Endemic Genera of Seed Plants in China, Science Press. Conservation and restoration of typical critically endangered plants with extremely small populations. Acta Ecologica Sinica, 36(22).

Conservation and restoration technologies for typical Wild Plants with Extremely Small Populations (WPESP). Acta Ecologica Sinica, 36(22): 7130-7135. Individual morphological and anatomical features of Populus.

euphratica Populus pruinosa relationship different developmental stages Alaer:

Tarim University. Morphological and anatomical characteristics of heteromorphic leaves in Populus euphratica and Populus pruinosa in relation to ontogenetic stages. Tarim University. ZHENG strategies acclimation growth light intensity exotic herbaceous species different ecological traits Xishuangbanna, China. Acta Ecologica Sinica, 25(4):

Adaptation strategies of two exotic herbaceous species with different ecological characteristics to growth light intensity in Xishuangbanna. Acta Ecologica Sinica, 25(4): 732. Functional traits of typical karst forest plants under different niches. Journal of Central South University of Forestry and Technology, 42(10):

Characteristics of leaf functional traits of typical karst forest plants in different micro-habitats. Journal of Central South University of Forestry and Technology, 42(10): 140.