水分胁迫下施磷对潮土玉米苗期叶片光合速率、保护酶及植株养分含量的影响

水分胁迫是潮土区玉米苗期生长的主要限制性因素,本研究采用水磷二因素完全随机设计的盆栽试验,设水分胁迫(W_1,田间持水量的70%~75%)和充分供水(W_2,田间持水量的85%~90%)2个水分处理;磷素处理设对照不施磷(P1)、施磷0.05 g·kg~(-1)土(P2)、0.10 g·kg~(-1)土(P3)、0.15 g·kg~(-1)土(P_4)和0.20 g·kg~(-1)(P5)5个处理,研究水分胁迫下施磷对玉米苗期叶片光合特性、酶活性及养分吸收的影响,为潮土区农田水分和磷素合理施用提供科学依据。研究结果表明:水分胁迫(W1)降低了玉米苗期净光合速率(Pn),W_1较W_2叶片Pn平均降低了27.96%;显著提高了玉米苗期丙二醛(MDA)含量,平均提高41.93%,水分胁迫还降低了过氧化物酶(POD)和过氧化氢酶(CAT)活性。在W1条件下施磷达到P_2水平叶片Pn即显著提高27.56%,而在W_2条件下施磷量只有达到P_4、P_5高水平时Pn才显著提高,在W_1条件下施磷对MDA的抑制效果明显弱于W_2。W_1条件下施磷量在P3水平POD和CAT活性最高,而在W_2条件下POD和CAT活性在P4达到最大值。W_1条件下适宜的施磷量(P_2至P_4)可以增加苗期玉米植株氮磷含量,但对钾含量影响较小;在W_2条件下增施磷有利于植株氮磷含量的增加,但钾素含量出现降低。综上,适宜的施磷量对潮土玉米苗期水分胁迫有一定的补偿作用,在本试验条件下,P_3处理在水分胁迫下更利于光合产物积累和玉米苗期抗逆性提高。

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.