氯化镧对硝酸盐胁迫下黄瓜幼苗光合特性的缓解效应

采用水培方式研究了LaCl₃对140 mmol·L^-1 NO₃-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LaCl3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（20 μmol·L^-1）LaCl3显著增加了叶片类胡萝卜素含量；LaCl₃还具有降低气孔关闭、改善叶片气体交换功能，减缓叶片F_v/F_m、Ф_PSII、AQY、CE及q_P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.20 μmol·L^-1 LaCl₃可以有效缓解硝酸盐对黄瓜幼苗光合作用的影响，而200 μmol·L^-1LaCl₃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.

Alleviation effects of LaCl3 on photosynthetic characteristics of cucumber seedlings under nitrate stress

By the method of hydroponic culture,this paper studied the alleviation effects of LaCl_3 on the photosynthetic characteristics of cucumber seedlings under nitrate(140 mmol NO_3~-·L~(-1)) stress,with the related mechanisms discussed.Under nitrate stress,the seedlings leaf chlorophyll and carotenoids contents decreased significantly,and the leaf Mg~(2+)-ATPase,Ca~(2+)-ATPase activities also decreased.On the 7th day of nitrate stress,the decrease of seedlings photosynthetic rate was mainly clue to stomatal limitation; but on the 12th day of nitrate stress,the decrease was mainly clue to no-stomatal limitation.Supplement with LaCl_3 could make the cucumber seedlings keep relatively higher leaf Mg~(2+)-ATPase and Ca~(2+)-ATPase activities and chlorophyll and carotenoids contents,and applying 20 μmol·L~(-1) of LaCl_3 could increase the carotenoids content significantly.LaCl_3 could also improve the leaf gas exchange,and alleviate the decrease of leaf F_v/F_m,Ф_(PSII),AQY,CE,and qp under nitrate stress,which helped the leaves making good use of light energy and maintaining higher CO2 assimilation capacity.An additional 20 μmol·L~(-1) of LaCl_3 could alleviate the nitrate stress on the photosynthesis of cucumber seedlings efficiently,but an additional 200μmol·L~(-1) of LaCl_3 only had the alleviation effect at the initial period of nitrate stress.Our results could benefit to the improvement of greenhouse soil.