[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.
Gao
Qing-Hai
QH
College of Life Sciences, Anhui Science and Technology University, Fengyang 233100, Anhui, China. gaoqh1977@163.com
Wu
Yan
Y
Wang
Xiu-Feng
XF
Lu
Xiao-Min
XM
Shi
Qing-Hua
QH
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