2年生希蒙得木幼苗对干旱胁迫的光合生理响应

采用盆栽控水的方法,研究了不同程度干旱胁迫(干旱0 d6、d1、2 d、18 d)对2年生希蒙得木叶片光合特性的影响。结果表明,希蒙得木叶片相对含水量(LRWC)随土壤含水量(SWC)的降低而显著降低,且SWC与LRWC呈极显著正相关;叶绿素含量、净光合速率(Pn)、气孔导度(Gs)、蒸腾速率(Tr)和最大净光合速率(Pnmax)均随干旱时间的增加而显著降低,暗呼吸速率(Rd)显著增加,胞间CO2浓度(Ci)呈先降低(D12)后升高(D18)的趋势,但水分利用效率(WUE)与Ci呈相反的变化趋势;干旱12 d处理下希蒙得木叶片光合能力下降的主要原因可能是气孔限制,而干旱18 d后植株光合能力下降的主要原因可能是非气孔限制;此外,表观量子产量(AQY)和光饱和点(LSP)均随干旱胁迫程度的增加而显著下降,并伴随着光补偿点(LCP)的急剧升高。由此表明,干旱条件下,希蒙得木叶片水分严重亏缺,光合碳同化能力及对光环境的适应能力降低,这也可能是植株应对干旱逆境的生存策略。

The Photosyn-physiological Responses of Two-year-old Simmondsia chinensis Saplings to Drought Stress

Effect of different drought stress continuous drought 0 d(D0),6 d(D6),12 d(D12),18 d(D18)] on photosynthetic characteristic of two-year-old S.chinensis seedlings by a pot experiment.The results showed that the leaf relative water content(LRWC) significantly decreased with the decrease of soil water content(SWC),and a highly significant positive correlation was observed between SWC and LRWC.The chlorophyll content,net photosynthetic rate(Pn),stomatal conductance(Gs),transpiration rate(Tr) and maximum net photosynthetic rate(Pnmax) decreased with the increase of drought stress time,while dark respiration rate(Rd) increased.Intercellular CO2 concentration(Ci) decreased under D12,but increased rapidly under D18.Water use efficiency(WUE) showed the opposite side to Ci.The decrease of photosynthetic capacity of S.chinensis seedlings under D12 was mainly due to stomatal limitation,while non-stomatal limitation might be the main reason under D18.In addition,apparent quantum yield(AQY) and light saturation point(LSP) decreased with the increase of drought stress,while light compensation point(LCP) increased.In conclusion,the leaf of S.chinensis seedlings under drought condition showed serious water deficit in leaf,and significantly decrease of photosynthetic carbon assimilation capacity and light environment adaptability.These responses might be the adaptation strategy of seedlings under drought stress.