小黑杨和桑树叶片光合特性对不同氮素形态的响应

Responses of photosynthetic characteristics in leaves of Populus simonii×P. nigra and Morus alba to nitrogen forms

为明确小黑杨和桑树光合功能对不同形态氮素的响应,利用水培试验研究了小黑杨和桑树幼苗叶片光合气体交换参数和叶绿素荧光参数对硝态氮(NO_3^--N)和氨态氮(NH_4^+-N)的响应。结果表明:在硝态氮(NO_3^--N)和氨态氮(NH_4^+-N)处理下,小黑杨的光合特性大致形似;桑树在氨态氮(NH_4^+-N)处理下桑树叶片的桑树幼苗叶片的P_n、G_s和T_r显著低于硝态氮(NO_3^--N)处理,同时F_v/F_m、F_v/F_o、Ф_(PSⅡ)、ETR、q_P也显著低于硝态氮(NO_3^--N)处理,NPQ显著高于硝态氮(NO_3^--N)处理;在氨态氮(NH_4^+-N)处理下桑树叶片PSⅡ光化学活性明显降低,激发能更多以无效热能的形式耗散。

In order to clarity the response of photosynthetic function to different forms of nitrogen in Populus nigra and Morus nigra, The responses of photosynthetic gas exchange and chlorophyll fluorescence parameters in leaves of Populus simonii×P.nigra and mulberry（Moros alba） to nitrate nitrogen（（NO3--N） and ammonium nitrogen（NH4＋-N） were investigated by solution culture method.The results showed that the photosynthesis characteristics of Populus simonii×P.nigra leaves with fertilization of nitrate nitrogen（NO3--N） were similar to that with fertilization of ammonium nitrogen（NH4＋-N）. The net photosynthetic rate（Pn）, stomatal conductance（Gs） and transpiration rate（Tr） of mulberry leaves with fertilization of ammonium nitrogen（NH4＋-N） were significantly lower than that with fertilization of nitrate nitrogen（NO3--N）, the maximum quantum yield（Fv/Fm）, Fv/Fo, actual photochemical efficiency（ФPSⅡ）, electron transfer rate（ETR）, photochemical quenching coefficient（qP） of mulberry leaves with fertilization of ammonium nitrogen（NH4＋-N） were significantly lower than that with fertilization of nitrate nitrogen（NO3--N） too. The nonphotochemical quenching（NPQ） of mulberry leaves with fertilization of ammonium nitrogen（NH4＋-N） were significantly higher than that with fertilization of nitrate nitrogen（NO3--N）. The photochemical activity of mulberry in leaves significantly decreased, the higher proportion of excitation energy dissipated in the invalid form of thermal energy.