The water adaptability of Jatropha curcas is modulated by soil nitrogen availability

Seedlings of Jatropha curcas L. were exposed to three watering (80, 50 and 30% field capacity, FC) and two nitrogen (N) regimes (with and without N-fertilization) in a greenhouse experiment. The objective of this study is to understand the responses of J. curcas to different water and nitrogen levels. Results showed that under 80% and 50% FC without N-fertilization J. curcas had larger allocation to root, however, leaf N content, pigment content and maximal efficiency of PSII decreased, and large numbers of starch grain accumulated in the chloroplast, resulting in a reduction of net photosynthesis rate; accordingly, oxidative stress occurred with the increase of oxidative production content, and J. curcas enhanced ascorbic acid content and free proline content to confront the stress. Furthermore, due to the low leaf N content and the accumulation of starch grain in chloroplast, low soluble protein and high soluble sugar content were observed. N-fertilization could alleviate the damage to plants of 80% and 50% FC under the given soil N condition. In addition, N-fertilization increased the water use efficiency. However, under 30% FC for the given soil N condition, J. curcas had not suffered damage at physiological and biochemical levels, and N-fertilization had no significantly positive effects on it. Thus we concluded that water adaptability of J. curcas was modulated by soil nitrogen availability.