干旱胁迫对不同施氮水平麻疯树幼苗光合特性及生长的影响

采用盆栽控水的方法，研究了干旱胁迫（连续干旱0 d，5 d，10 d，…，45 d）对不同施氮水平(对照 0 kg N·hm^-2、低氮 96 kg N·hm^-2、中氮 288 kg N·hm^-2、高氮 480 kg N·hm^-2)麻疯树幼苗光合特性及其生长的影响.结果表明: 随干旱胁迫强度的增加，各施氮水平麻疯树幼苗叶片相对含水量、苗高生长量、地径生长量、叶面积、净光合速率、蒸腾速率和气孔导度均降低，且各水分处理间差异极显著(P<0.01)；随干旱时间的延长，叶绿素含量和水分利用效率表现出先升高后降低的趋势，而胞间CO₂浓度呈先降低后升高的趋势.正常供水时，施氮处理均不同程度提高了麻疯树幼苗的光合能力，促进了麻疯树幼苗的生长，且施氮量越高效果越好；干旱条件下，氮素营养对植株光合能力和生长的影响与干旱程度和施氮水平有关.轻度干旱时，提高施氮水平对植株光合能力和生长具有明显的促进作用；中度干旱时，中氮的促进作用明显高于其他施氮水平；严重干旱时，低氮的促进效果最好，高氮的促进作用减弱并逐渐转向抑制.

Effect of drought stress on photosynthetic characteristics and growth of Jatropha curcas seedlings under different nitrogen levels

A pot experiment with controlled water supply was conducted to study the effects of drought stress(continuous drought for0 d,5 d,10 d,…,45 d)on the photosynthetic characteristics and growth of Jatropha curcas seedlings under different nitrogen fertilization levels(N0,0 kg N·hm~(-2); NL,96 kg N·hm~(-2); N_M,288 kg N·hm~(-2); NH,480 kg N·hm~(-2)).With the enhancement of drought stress,the leaf relative water content(RWC1),height growth(Z_h),basal diameter growth(Z_d),leaf area(L_a),net photosynthetic rate(P_n),transpiration rate(T_r),and stomatal conductance(G_s)decreased significantly(P <0.01),irrespective of nitrogen fertilization level.The chlorophyll(Chl)content and water use efficiency(WUE)increased first and decreased then,while the intercellular CO_2 concentration(C_i) had an increase after an initial decrease.Under adequate water condition,nitrogen fertilization promoted the photosynthesis and growth of J.curcas seedlings to different degrees,and the effect was increased with increasing nitrogen fertilization level.Under drought stress,the effects of nitrogen nutrition on the photosynthesis and growth were dependent on drought intensity and nitrogen fertilization level.Specifically,in creasing nitrogen fertilization level could promote the photosynthesis and growth of J.curcas seedlings under mild drought,the promotion effect of N_M was higher than that of N_L and N_H under mod erate drought,and N_L had the best promotion effect while N_H weakened the effect or made it nega tive under severe drought.