Xu Xiang Zeng, Zhang Jin Yan, Zhang Guang Hui, Long Guang Qiang, Yang Sheng Chao, Chen Zhong Jian, Wei Fu Gang, Chen Jun Wen
National & Local Joint Engineering Research Center on Gemplasm Utilization & Innovation of Chinese Medicinal Materials in Southwest China, Yunnan Agricultural University, Kunming 650201, China.
College of Agronomy and Biotechnology, Yunnan Agricultural University, Kunming 650201, China.
Ying Yong Sheng Tai Xue Bao. 2018 Jan;29(1):193-204. doi: 10.13287/j.1001-9332.201801.008.
To explore the effects of light intensity on photosynthetic characteristics and light adaptation of the shade-demanding species Panax notoginseng, the responses of photosynthesis to photosynthetic photon flux density, CO and sunflecks in the two-year-old Panax notoginseng were investigated under different levels of light intensity (29.8%, 9.6%, 5.0%, 1.4% and 0.2% of full sunlight). Meanwhile, chlorophyll a fluorescence parameter and light energy partitioning were also recorded and calculated in the responsive process. P. notoginseng grown under 29.8% full sunlight (FL) had a lower apparent quantum yield (AQY), potential photochemical quantum yield (F/F) and potential photochemical activity (F/F), however, it had a higher maximum net photosynthetic rate (P), maximum electron transport rate (J), F/F', electron transport rate (ETR), photochemical quenching (q) and the proportion of light energy allocated to photochemistry dissipation (ΦPS), but the non-photochemical quenching (NPQ) was not the highest. There were no significant differences in P, light compensation point (LCP), light saturation point (LSP), dark respiration rate (R) among 9.6%FL and 5.0% FL treatments, but these treatments had relatively higher values of NPQ, AQY, carboxylation efficiency (CE), maximum carboxylation rate (V), F/F and F/F. In addition, the P, CE, V, J, ETR,F/F', q, NPQ and Φ decreased with the decrease in light intensity from 5.0%FL to 0.2%FL, and the proportion of light energy allocated to fluorescent dissipation (Φ) were increased. Under 500 μmol·m·s light-flecks inducting, the Φof P. notoginseng increased slowly with the extension of time except for the treatment of less than 5.0%FL, and under the circumstance of 1.4%FL and 0.2%FL, Φreached significantly a perfect result, moreover, Φincreased rapidly. These results suggested that the enhancement in photosynthetic electron transport to use the light energy and the moderate photoinhibition of PS2 might avoid the irreversible oxidative damage of photosynthetic organization in P. notoginseng under high levels of light intensity. Moderate shading was beneficial to maintain its higher non-photochemical quenching ability. However, its photosynthetic capacity depressed and the proportion of light energy allocated to non-photochemical pathway increased obviously in excessive shading, and it easily caused a light oxidative damage.
为探讨光强对喜阴植物三七光合特性及光适应的影响，研究了两年生三七在不同光强水平（全日照的29.8%、9.6%、5.0%、1.4%和0.2%）下光合作用对光合光子通量密度、CO₂和光斑的响应。同时，在响应过程中还记录并计算了叶绿素a荧光参数和光能分配情况。在全日照29.8%（FL）条件下生长的三七表观量子产率（AQY）、潜在光化学量子产率（Fv/Fm）和潜在光化学活性（Fv/Fo）较低，但其最大净光合速率（Pn）、最大电子传递速率（J）、Fv'/Fm'、电子传递速率（ETR）、光化学猝灭（qP）和分配到光化学耗散的光能比例（ΦPSⅡ）较高，而非光化学猝灭（NPQ）并非最高。9.6%FL和5.0%FL处理之间的Pn、光补偿点（LCP）、光饱和点（LSP）、暗呼吸速率（Rd）无显著差异，但这些处理的NPQ、AQY、羧化效率（CE）、最大羧化速率（Vcmax）、Fv/Fm和Fv/Fo值相对较高。此外，从5.0%FL降至0.2%FL，随着光强降低，Pn、CE、Vcmax、J、ETR、Fv'/Fm'、qP、NPQ和ΦPSⅡ降低，分配到荧光耗散的光能比例（ΦF）增加。在500 μmol·m⁻²·s⁻¹光斑诱导下，除光强低于5.0%FL的处理外，三七的ΦF随时间延长缓慢增加，在1.4%FL和0.2%FL条件下，ΦF显著达到较好结果，且增加迅速。这些结果表明，在高光强下，三七光合电子传递增强以利用光能以及PSⅡ适度光抑制可能避免光合机构的不可逆氧化损伤。适度遮荫有利于维持其较高的非光化学猝灭能力。然而，过度遮荫会使其光合能力下降，分配到非光化学途径的光能比例明显增加，且易造成光氧化损伤。
