Yu Zheng-Chao, Lin Wei, He Wei, Yan Guan-Zhao, Zheng Xiao-Ting, Luo Yan-Na, Zhu Hui, Peng Chang-Lian
Guangdong Provincial Key Laboratory of Biotechnology for Plant Development, Guangzhou Key Laboratory of Subtropical Biodiversity and Biomonitoring, School of Life Sciences, South China Normal University, Guangzhou 510631, China.
School of Life Sciences and Food Engineering, Hanshan Normal University, Chaozhou 521041, China.
Tree Physiol. 2023 Jun 7;43(6):965-978. doi: 10.1093/treephys/tpad026.
Many studies have investigated the photoprotective and photosynthetic capacity of plant leaves, but few have simultaneously evaluated the dynamic changes of photoprotective capacity and photosynthetic maturation of leaves at different developmental stages. As a result, the process between the decline of photoprotective substances and the onset of photosynthetic maturation during plant leaf development are still poorly understood, and the relationship between them has not been quantitatively described. In this study, the contents of photoprotective substances, photosynthetic pigment content and photosynthetic capacity of leaves at different developmental stages from young leaves to mature leaves were determined by spatio-temporal replacement in eight dominant tree species in subtropical evergreen broadleaved forests. The correlation analysis found that the data sets of anthocyanins, flavonoids, total phenolics and total antioxidant capacity were mainly distributed on one side of the symmetry axis (y = x), while the data sets of flavonoids, total phenolics and total antioxidant capacity were mainly distributed on both sides of the symmetry axis (y = x). In addition, the content of photoprotective substances in plant leaves was significantly negatively correlated with photosynthetic pigment content and photosynthetic capacity but was significantly positively correlated with dark respiration rate (Rd). When chlorophyll accumulated to ~50% of the final value, the photoprotective substance content and Rd of plant leaves reached the lowest level, and anthocyanins disappeared completely; in contrast, the photosynthetic capacity reached the highest level. Our results suggest that anthocyanins mainly play a light-shielding role in the young leaves of most plants in subtropical forests. In addition, 50% chlorophyll accumulation in most plant leaves was the basis for judging leaf photosynthetic maturity. We also believe that 50% chlorophyll accumulation is a critical period in the transition of plant leaves from high photoprotective capacity (high metabolic capacity, low photosynthetic capacity) to low photoprotective capacity (low metabolic capacity, high photosynthetic capacity).
许多研究调查了植物叶片的光保护和光合能力，但很少有研究同时评估不同发育阶段叶片光保护能力和光合成熟度的动态变化。因此，在植物叶片发育过程中，光保护物质含量下降与光合成熟开始之间的过程仍知之甚少，它们之间的关系也尚未得到定量描述。在本研究中，通过时空替代法测定了亚热带常绿阔叶林8种优势树种从幼叶到成熟叶不同发育阶段叶片的光保护物质含量、光合色素含量和光合能力。相关性分析发现，花青素、黄酮类化合物、总酚和总抗氧化能力的数据集主要分布在对称轴（y = x）的一侧，而黄酮类化合物、总酚和总抗氧化能力的数据集主要分布在对称轴（y = x）的两侧。此外，植物叶片中光保护物质的含量与光合色素含量和光合能力呈显著负相关，但与暗呼吸速率（Rd）呈显著正相关。当叶绿素积累到最终值的~50%时，植物叶片的光保护物质含量和Rd达到最低水平，花青素完全消失；相反，光合能力达到最高水平。我们的研究结果表明，花青素在亚热带森林中大多数植物的幼叶中主要起遮光作用。此外，大多数植物叶片中叶绿素积累50%是判断叶片光合成熟的依据。我们还认为，叶绿素积累50%是植物叶片从高光保护能力（高代谢能力，低光合能力）向低光保护能力（低代谢能力，高光合能力）转变的关键时期。
