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采用水培方式研究了LaC l3对140 mmol.L-1NO3-硝酸盐胁迫下黄瓜幼苗光合特性的影响.结果表明:硝酸盐胁迫显著降低了黄瓜幼苗叶绿素及类胡萝卜素含量,叶片Mg2+-ATPase、Ca2+-ATPase活性也随之降低;硝酸盐胁迫7 d,黄瓜幼苗叶片光合速率的降低以气孔限制为主,叶片AQY与CE下降,胁迫12 d则以非气孔限制为主.硝酸盐胁迫下,外加LaC l3可以使黄瓜叶片保持较高的Mg2+-ATPase、Ca2+-ATPase活性及叶绿素和类胡萝卜素含量,尤其是外加低浓度(20μmol.L-1)LaC l3显著增加了叶片类胡萝卜素含量;LaC l3还具有降低气孔关闭、改善叶片气体交换功能,减缓叶片Fv/Fm、ФPSII、AQY、CE及qP的降低幅度等作用,使叶片在盐胁迫下保持较高的光能利用率及CO2同化能力.20μmol.L-1LaC l3可以有效缓解硝酸盐对黄瓜幼苗光合作用的影响,而200μmol.L-1LaC l3在胁迫初期对黄瓜幼苗有缓解效果,后期则效果不明显.该结果可为设施土壤的改良提供新的途径.
The effects of LaCl3 on the photosynthetic characteristics of cucumber seedlings under 140 mmol·L-1NO3-nitrate stress were studied by hydroponic culture.The results showed that the nitrate content significantly reduced the content of chlorophyll and carotenoid in cucumber seedlings, and the contents of Mg2 + -ATPase, Ca2 + -ATPase activity also decreased. Under the nitrate stress, the decrease of photosynthetic rate in leaves of cucumber seedlings was dominated by stomatal limitation and decreased with AQY and CE, but non-stomatal limitation was the dominant stress at 12 d of nitrate stress. Under nitrate stress, In addition, LaCl3 could maintain high Mg2 + -ATPase, Ca2 + -ATPase activity and chlorophyll and carotenoid content in cucumber leaves, especially the addition of low concentration (20μmol.L-1) LaCl3 significantly increased leaf carotenoid content; LaCl3 also had the effects of reducing the stomatal closure, improving the gas exchange function of leaves and slowing down the decrease of Fv / Fm, ФPSII, AQY, CE and qP, and keeping the light utilization efficiency and CO2 assimilation under salt stress 20μmol.L-1LaC l3 can effectively alleviate the effects of nitrate on the photosynthesis of cucumber seedlings, while 200μmol.L-1LaC l3 can alleviate the cucumber seedlings in the early stage of stress, but the effect is not obvious at the later stage. Soil improvement facilities provide a new way.