Ma Xiaohua, Song Lili, Yu Weiwu, Hu Yuanyuan, Liu Yang, Wu Jiasheng, Ying Yeqing
Nurturing Station for the State Key Laboratory of Subtropical Silviculture, Zhejiang A & F University Hangzhou, China ; School of Forestry and Biotechnology, Zhejiang A & F University Hangzhou, China.
Front Plant Sci. 2015 May 8;6:321. doi: 10.3389/fpls.2015.00321. eCollection 2015.
Light intensity critically affects plant growth. Camptotheca acuminata is a light-demanding species, but its optimum light intensity is not known. To investigate the response of C. acuminata seedlings to different light intensities, specifically 100% irradiance (PAR, 1500 ± 30 μmol m(-2) s(-1)), 75% irradiance, 50% irradiance, and 25% irradiance, a pot experiment was conducted to analyze growth parameters, photosynthetic pigments, gas exchange, chlorophyll fluorescence, stomatal structure and density, chloroplast ultrastructure, ROS concentrations, and antioxidant activities. Plants grown under 75% irradiance had significantly higher total biomass, seedling height, ground diameter, photosynthetic capacity, photochemical efficiency, and photochemical quenching than those grown under 100%, 25%, and 50% irradiance. Malondialdehyde (MDA) content, relative electrolyte conductivity (REC), superoxide anion (O(.-) 2) production, and peroxide (H2O2) content were lower under 75% irradiance. The less pronounced plant growth under 100% and 25% irradiance was associated with a decline in photosynthetic capacity and photochemical efficiency, with increases in the activity of specific antioxidants (i.e., superoxidase dismutase, peroxidase, and catalase), and with increases in MDA content and REC. Lower levels of irradiance were associated with significantly higher concentrations of chlorophyll (Chl) a and b and lower Chla/b ratios. Stomatal development was most pronounced under 75% irradiance. Modification of chloroplast development was found to be an important mechanism of responding to different light intensities in C. acuminata. The results indicated that 75% irradiance is optimal for the growth of C. acuminata seedlings. The improvement in C. acuminata growth under 75% irradiance was attributable to increased photosynthesis, less accumulation of ROS, and the maintenance of the stomatal and chloroplast structure.
光照强度对植物生长有着至关重要的影响。喜树是一种喜光物种，但其最适光照强度尚不清楚。为了研究喜树幼苗对不同光照强度（具体为100%光照强度（光合有效辐射，PAR，1500±30 μmol m(-2) s(-1)）、75%光照强度、50%光照强度和25%光照强度）的响应，进行了盆栽试验，以分析生长参数、光合色素、气体交换、叶绿素荧光、气孔结构和密度、叶绿体超微结构、活性氧浓度和抗氧化活性。与在100%、25%和50%光照强度下生长的植株相比，在75%光照强度下生长的植株具有显著更高的总生物量、苗高、地径、光合能力、光化学效率和光化学猝灭。在75%光照强度下，丙二醛（MDA）含量、相对电导率（REC）、超氧阴离子（O(.-) 2）产生量和过氧化氢（H2O2）含量较低。在100%和25%光照强度下植株生长不明显与光合能力和光化学效率下降、特定抗氧化剂（即超氧化物歧化酶、过氧化物酶和过氧化氢酶）活性增加以及MDA含量和REC增加有关。较低的光照强度与叶绿素（Chl）a和b浓度显著升高以及Chla/b比值降低有关。气孔发育在75%光照强度下最为明显。发现叶绿体发育的改变是喜树对不同光照强度响应的重要机制。结果表明，75%光照强度是喜树幼苗生长的最佳条件。喜树在75%光照强度下生长的改善归因于光合作用增强、活性氧积累减少以及气孔和叶绿体结构的维持。
