[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 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.
College of Life Sciences, Anhui Science and Technology University, Fengyang 233100, Anhui, China. gaoqh1977@163.com
Qing-Hai
QH
Gao
Yan
Y
Wu
Xiu-Feng
XF
Wang
Xiao-Min
XM
Lu
Qing-Hua
QH
Shi
D002734:Chlorophyll / Q000032:analysis; D018553:Cucumis sativus / Q000187:drug effects / Q000502:physiology*; D007811:Lanthanum / Q000494:pharmacology*; D009566:Nitrates / Q000633:toxicity*; D010788:Photosynthesis / Q000502:physiology*; D036226:Seedlings / Q000502:physiology*; D013312:Stress, Physiological
D009566:Nitrates; C028521:lanthanum chloride; D002734:Chlorophyll; D007811:Lanthanum