干旱胁迫对巨桉幼树生长及光合特性的影响

Effects of Drought Stress on Growth and Photosynthetic Characteristics of Eucalyptus Grandis Saplings

采用盆栽和持续干旱的方法,研究了干旱胁迫(以2 d为1个处理期,随干旱处理时间延长分别记为D2,D4,D6,D8,D10,D12,D14,正常浇水记为D0)对巨桉（Eucalyptus grandis）幼树生长及光合特性的影响。结果表明:（1）在干旱胁迫6 d以内,尽管巨桉幼树地径和株高增量降低,但与D0差异不明显;随着胁迫时间的增加（816 d）,地径和株高增量显著降低（P<0.05）;（2）随着胁迫时间的增加,叶绿素a含量显著降低（P<0.05）,叶绿素a/b比值总体呈先升高后降低的趋势,叶绿素b和类胡萝卜素含量除D2与D0差异不显著外,其余各干旱处理均显著小于D0（P<0.05）;（3）随着胁迫时间的增加,巨桉幼树叶片净光合速率（Pn）、蒸腾速率（Tr）、气孔导度（Gs）均呈明显降低趋势,胞间CO2浓度（Ci）呈先降低后升高的趋势;（4）随着胁迫时间的增加,表观量子效率（YAQ）、Ru BP羧化速率（EC）、光饱和点（Lsp）与CO2饱和点(Csp)均呈下降趋势,光补偿点(Lcp)、CO2补偿点(Ccp)呈上升趋势,最大净光合速率(Pn,max)呈下降趋势。综上所述,随着干旱程度的加重,巨桉幼树叶片光合色素含量减少,气孔部分关闭,光合器官在一定程度上遭到破坏,对光与CO2的利用能力降低,光合速率下降,最终使巨桉幼树的生长受到限制。

To study effects of drought stress on growth and photosynthetic characteristics of Eucalyptus grandis saplings, a pot experiment kept under continuous drought was performed. Growth and photosynthetic parameters of the saplings were monitored once every two days after irrigation, that is, on D2, D4, D6, D8, D10, D12, D14 and D16, while the sam-pling with normal irrigation as DO. Results show that ( 1) during the first 6 days, although growth of the saplings in ground diameter and plant height declined, it did not differ much from that on D0 ( P>0. 05);however, with the stress going on ( D8-D16) , the growth of the saplings in ground diameter and plant height dropped significantly. ( 2) with the stress going on, the content of chlorophyll a ( Chl a) in the saplings decreased significantly ( P<0. 05) , whereas chlorophyll a/ chloro-phyll b ratio( Chl a/b) followed a rising-and-then-falling trend, and the content of Chlorophyll b and carotenoids on D2 did not change much from their respective ones on D0( P>0. 05) , but were getting much lower from D4 than those on D0( P<0. 05);(3) with the stress going on, net photosynthetic rate (Pn), transpiration rate (Tr), stomatal conductance (Gs) of the saplings decreased significantly ( P<0. 05) while intercellular CO2 concentration ( Ci ) decreased first and then in-creased;(4) with the stress going on, apparent quantum yield(YAQ), RuBP apparent carboxylation rate (Ec), light sat-uration point(Lsp) and CO2saturation point(Csp) of the saplings were all on declining trends, while light compensation point(Lcp), CO2 compensation point(Ccp) on rising ones and maximum net photo-syntheticrate(Pmax)was on a declining one. In summary, with the drought stress aggravating, the content of photosynthetic pigments in the saplings decreased;stomata closed partly;photosynthetic organs were damaged to some extent, thus greatly reducing the saplings′ability to use light and CO2 and their photosynthetic rate, and consequently suppressing growth of the E. grandis saplings.