Gao Qing-Hai, Wu Yan, Wang Xiu-Feng, Lu Xiao-Min, Shi Qing-Hua
College of Life Sciences, Anhui Science and Technology University, Fengyang 233100, Anhui, China.
Ying Yong Sheng Tai Xue Bao. 2009 Nov;20(11):2685-90.
By the method of hydroponic culture, this paper studied the alleviation effects of LaCl3 on the photosynthetic characteristics of cucumber seedlings under nitrate (140 mmol NO3(-) x L(-1)) stress, with the related mechanisms discussed. Under nitrate stress, the seedlings leaf chlorophyll and carotenoids contents decreased significantly, and the leaf Mg2+-ATPase, Ca2+-ATPase activities also decreased. On the 7th day of nitrate stress, the decrease of seedlings photosynthetic rate was mainly due to stomatal limitation; but on the 12th day of nitrate stress, the decrease was mainly due to no-stomatal limitation. Supplement with LaCl3 could make the cucumber seedlings keep relatively higher leaf Mg2+-ATPase and Ca2+-ATPase activities and chlorophyll and carotenoids contents, and applying 20 micromol x L(-1) of LaCl3 could increase the carotenoids content significantly. LaCl3 could also improve the leaf gas exchange, and alleviate the decrease of leaf Fv/Fm, PhiPSII, 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 micromol x L(-1) of LaCl3 could alleviate the nitrate stress on the photosynthesis of cucumber seedlings efficiently, but an additional 200 micromol x L(-1) of LaCl3 only had the alleviation effect at the initial period of nitrate stress. Our results could benefit to the improvement of greenhouse soil.
采用水培法,研究了LaCl₃对硝酸盐(140 mmol NO₃⁻·L⁻¹)胁迫下黄瓜幼苗光合特性的缓解效应,并探讨了相关机制。在硝酸盐胁迫下,幼苗叶片叶绿素和类胡萝卜素含量显著降低,叶片Mg²⁺-ATP酶、Ca²⁺-ATP酶活性也降低。在硝酸盐胁迫第7天,幼苗光合速率下降主要是由于气孔限制;但在硝酸盐胁迫第12天,下降主要是由于非气孔限制。补充LaCl₃可使黄瓜幼苗保持相对较高的叶片Mg²⁺-ATP酶和Ca²⁺-ATP酶活性以及叶绿素和类胡萝卜素含量,施用20 μmol·L⁻¹的LaCl₃可显著提高类胡萝卜素含量。LaCl₃还可改善叶片气体交换,缓解硝酸盐胁迫下叶片Fv/Fm、PhiPSII、AQY、CE和qp的下降,有助于叶片更好地利用光能并维持较高的CO₂同化能力。额外施用20 μmol·L⁻¹的LaCl₃可有效缓解硝酸盐对黄瓜幼苗光合作用的胁迫,但额外施用200 μmol·L⁻¹的LaCl₃仅在硝酸盐胁迫初期有缓解作用。我们的结果有助于温室土壤的改良。