遮荫处理对秋枫幼苗生理生态特性的影响

为了解遮荫对秋枫(Bischofia javanica)幼苗生长的影响,对夏季1年生秋枫幼苗在4种遮荫(透光率分别为自然光的100%、41.3%、14.6%和3.6%)处理150 d后的生理指标变化进行了研究。结果表明,1年生秋枫幼苗的光补偿点(LCP)、光饱和点(LSP)和暗呼吸速率(Rd)随着遮荫程度加重而减小,表观量子效率(AQY)则增大,净光合速率(Pn)、气孔导度(Gs)、蒸腾速率(Tr)和胞间CO_2浓度(Ci)的日变化表明秋枫有明显的"午休"现象,遮荫引起光合速率降低的主要原因是非气孔限制,而全光照条件下则是气孔限制。叶绿素、可溶性糖含量随遮荫程度的增大呈先升后降的变化趋势;相对电导率、丙二醛(MDA)含量、过氧化氢酶(CAT)活性则呈先降后升的趋势,以41.3%透光率的最小;可溶性蛋白质含量、超氧化物歧化酶(SOD)活性随遮荫程度的增大而降低。因此,秋枫幼苗主要通过提高Pn、抗氧化酶活性(SOD和CAT)、叶绿素含量,降低LSP、LCP和Rd,增大AQY来提高弱光利用能力;适度遮荫(41.3%NS)更有利于1年生秋枫幼苗在夏季的生长。

Effects of Shading on Physio-ecology Characteristics of Bischofia javanica Seedlings

In order to understand the effect of shading on growth of Bischofia javanica seedlings,the changes in physio-ecology characteristics of one-year-old Bischofia javanica seedlings were studied under different shading in summer,including 100% NS (nature sunshine),41.3% NS,14.6% NS and 3.6% NS for 150 days.The results showed that the light compensation point (LCP),light saturation point (LSP),dark respiration rate (Rd) increased with the increment of shading degree,and apparent photosynthetic quantum yield (AQY) increased continuously.The noon break phenomenon was obvious from the daily changes in net photosynthetic rate (Pn),stomatal conductance (Gs),intercellular CO₂ concentration (Ci) and transpiration rate (Tr) of B.javanica seedlings under different light conditions.The decreasing of photosynthetic rate was due to non-stomatal factor under shading,while that was to stomatal factor under whole sunshine.Along the increment of shade degree,the contents of chlorophyll and soluble sugar in B.javanica seedlings increased at first and then decrease,on the contrary of the relative conductance rate,malondialdehyde (MDA) content and CAT activity with the minimum values under 41.3% NS.The SOD activity and soluble protein content decreased with increment of shading degree.Therefore,the B.javanica seedlings would adapt to strong light environment by improving the Pn,antioxidant enzyme activities (SOD and CAT) and chlorophyll content,reducing LSP,LCP and Rd,increasing the AQY.It could grow better under moderate shading (41.3% NS) in summer.