RESUMO
A pot experiment with controlled water supply was conducted to study the effects of drought stress (continuous drought for 0 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 x hm(-2); N(L), 96 kg N x hm(-2; N(M), 288 kg N x hm(-2); N(H), 480 kg N x 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 CO2, 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, increasing 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 moderate drought, and N(L) had the best promotion effect while N(H) weakened the effect or made it negative under severe drought.
