遮荫对七子花幼苗光合特性和非结构性碳水化合物含量的影响

Effects of Shading on Photosynthetic Characteristics and Non-structural Carbohydrate Content of Heptacodium miconioides Seedlings

为探讨不同光环境下濒危植物七子花(Heptacodium miconioides)的生长及适应规律,以2年生七子花幼苗为研究对象,设置全光照、60%遮荫和90%遮荫3种光照强度,研究不同光环境对七子花幼苗的光合特性和非结构性碳水化合物(NSC)含量的影响。结果表明:(1)3种光照处理下,七子花幼苗的净光合速率(P_(n))日变化均呈“单峰型”曲线,P_(n)日均值为全光照>60%遮荫>90%遮荫,90%遮荫下水分利用效率(W_(UE))日均值显著低于全光照和60%遮荫。(2)与全光照相比,60%遮荫下七子花幼苗的光补偿点(L_(CP))和暗呼吸速率(R_(d))显著下降,而光饱和点(L_(SP))、最大净光合速率(P_(n_(max)))、最大羧化速率(V_(cmax))、最大电子传递速率(J_(max))和磷酸丙糖利用率(T_(PU))无显著差异;重度遮荫(90%遮荫)导致植株的P_(n_(max))、L_(SP)、L_(CP)、R_(d)、V_(cmax)、J_(max)和T_(PU)显著降低。(3)七子花幼苗叶片的淀粉、可溶性糖和NSC含量在60%遮荫处理中最高,90%遮荫处理下则显著下降。植株的NSC含量与P_(n)、V_(cmax)、J_(max)和T_(PU)呈显著正相关关系。综上所述,七子花在幼苗期具有一定的喜光性和耐荫能力,适度遮荫下植株可通过降低L_(CP)、R_(d)来调整叶片的光合生理,维持较高的NSC含量,从而来提高对弱光的利用率和碳同化能力,但在生产育苗过程中过度遮荫不利于七子花幼苗的生长。

To investigate the growth and adaptation of Heptacodium miconioides under different light conditions,two-year-old H.miconioides seedlings were used as materials under three light intensities(full light,60%shade and 90%shade),and the photosynthetic characteristics and non-structural carbohydrate(NSC)content of H.miconioides were measured.The results showed that:(1)The diurnal changes of net photosynthetic rate(P_(n))of H.miconioides seedlings under three light intensities showed“single-peak”curves.The daily mean values of P_(n) under three light intensities ranked as full light>60%shade>90%shade.The daily mean values of water use efficiency(W_(UE))under 90%shade treatment was significantly lower than those under full light and 60%shade treatments;(2)Compared with full light,the light compensation point(L_(CP))and dark respiration rate(R_(d))of H.miconioides seedlings under 60%shade decreased significantly,while the light saturation point(L_(SP)),maximum net photosynthetic rate(P_(nmax))),maximum carboxylation rate(V_(cmax)),maximum electron transport rate(J_(max)),and triose phosphate utilization rate(T_(PU))had no significant difference respectively.As shading degree increased,the L_(SP),P_(nmax)),L_(CP),R_(d),V_(cmax),J_(max) and T_(PU) of H.miconioides seedlings under 90%shade were significantly lower than those under full light and 60%shade treatments.(3)The contents of starch,soluble sugar and NSC in leaves of H.miconioides seedlings were highest under 60%shade treatment,and decreased significantly under 90%shade treatment.The NSC content of H.miconioides seedlings was significantly positively correlated with P_(n),V_(cmax),J_(max) and T_(PU) respectively.Therefore,H.miconioides had ability of photopholic and shade-tolerant at the seedling stage,and plants could adjust the photosynthetic characteristics of leaves by reducing L_(CP) and R_(d),and maintained a high NSC content under moderate shading conditions,thereby to improve the utilization rate of weak light and carbon assimilation ability,however,excessive shading was not conducive to the growth of H.miconioides seedlings.