Effect of phosphorus on leaf net photosynthesis, protective enzyme activity and nutrient uptake of maize at seedling stage in fluvo-aquic soils under water stress

Water stress is a major limiting factor of seedling maize in fluvo-aquic soils. A pot experiment was conducted under greenhouse conditions to study the effect of water stress and P application on net photosynthetic rate (P_n), leaf protective enzymes activities and nutrients contents of maize at seedling stage. The experiment consisted of two water and five P treatments. The water treatments included water stress (W₁, 70%-75% of field capacity) and sufficient water (W₂, 85%-90% of field capacity), the P treatments included 0 g(P)·kg^-1(soil) (P₁), 0.05 g(P)·kg^-1(soil) (P₂), 0.10 g(P)·kg^-1(soil) (P₃), 0.15 g(P)·kg^-1 (soil) (P₄) and 0.20 g(P)·kg^-1(soil) (P₅). The results showed that compared with W₂, W₁ treatment decreased P_n of maize leaf by 27.96%. Water stress significantly improved mean MDA content of maize leaf by 41.93%. But water stress decreased POD and CAT activities of maize leaf. Under W₁ treatment, P_n significantly increased by 27.56% at P₂ level over P₁ level, but further increased in P supply had no significantly promoting effect on P_n. The inhibition effect of P use on MDA under W₁ was significantly lower than that under W₂ treatment. The activities of POD and CAT were maximum at P₃ level under W₁, while those of POD and CAT were maximum at P₄ level under W₂ treatment. It was also noted that suitable P treatments (P₂, P₃ and P₄) beneficially increased N and P contents of maize plant, while it had little effect on K content under W₁ Treatment. Under W₂ treatment, increase in P supply beneficially increased N and P contents, but decreased K content of maize. In conclusion, suitable P application had a compensation effect on water stress in seedling maize in fluvo-aquic soils. Under the experimental conditions, P₃ treatment more favored the accumulation of photosynthetic processes and enhanced stress resistance of maize.