Mixed-nitrogen nutrition-mediated enhancement of drought tolerance of rice seedlings associated with photosynthesis, hormone balance and carbohydrate partitioning

Fig. 1 Leaf photosynthetic rate (Pn), stomatal conductance (gs), intercellular CO2 concentration (Ci), and transpiration rate (Tr) of rice plants subjected to different N forms and water regimens. N, NP, A, AP, NA and NAP represent the nitrate (NO3-), NO3-+PEG 6000, ammonium (NH4+), NH4++PEG 6000, mixture of NO3- and NH4+ (NO3-+NH4+) and NO3-+NH4++PEG 6000 treatments, respectively. The same occurs below. Fig. 2 Rice leaf Chl, total N, and Rubisco contents under the different N form and water conditions Fig. 3 Concentrations of ABA, IAA, and CTKs, and the IAA/CTK in the leaves and roots of rice seedlings subjected to different N forms and water regimens Fig. 4 Concentrations of soluble sugar and starch in the leaves and roots of rice seedlings subjected to different N forms and water regimens Fig. 5 Activities of sucrose-phosphate synthase (SPS) and sucrose synthase in the synthetic direction (SSs) in the leaves of rice seedlings subjected to different N forms and water regimens Fig. 6 Activities of acid invertase (InvA), neutral/alkaline invertase (InvN), and sucrose synthase in the cleavage direction (SSc) in the leaves of rice seedlings subjected to different N forms and water regimens Fig. 7 Activities of acid invertase (InvA), neutral/alkaline invertase (InvN), and sucrose synthase in the cleavage direction (SSc) in the roots of rice seedlings subjected to different N forms and water regimens.