Effects of Exogenous Sulfur on Photosynthetic Characteristics and Mineral Elements Absorption in Portulaca oleracea Under Cadmium Stress

doi:10.13560/j.cnki.biotech.bull.1985.2019-0672

Abstract

Abstract: Uncovering the physiological mechanism of exogenous sulfur inducing cadmium（Cd）tolerance in Portulaca oleracea from the aspect of photosynthetic reaction system may provide a theoretical foundation for application of S in alleviating the toxicity of heavy metals in plants. A hydroponic experiment was conducted to investigate the effects of exogenous（NH₄）₂SO₄,an S donor,on the photosynthetic pigments,photosynthetic characteristics,chlorophyll fluorescence parameters,and mineral element contents in P. oleracea treated with 100 mg/L CdCl₂. The results showed that Cd stress resulted in the significant decrease of chlorophyll a and b,also the net photosynthesis rate transpiration rate,and stomatal conductance,while the increase of intercellular concentrations of carbon dioxide（Ci）;these results indicated that nonstomatal factor was the dominant one that induced photosynthetic inhibition under Cd stress. Meanwhile,PSII actual photochemical efficiency（Ф_PSII）,electron transfer efficiency（J）,and chemical quenching coefficient（q_P）all significantly decreased,whereas nonchemical quenching coefficient（q_N）significantly increased;these results implied that Cd stress disturbed proper function of PSII in P. oleracea. However,the application of 400 mg/L（NH₄）₂SO₄ significantly increased the content of chlorophyll a and b,ratio of chlorophyll a/b,meanwhile enhanced both of the photosynthesis and quantum yield of PSII photochemistry. Furthermore,Cd treatment significantly increased content of calcium（Ca）and iron（Fe）,while inhibited absorption of magnesium（Mg）,manganese（Mn）,and copper（Cu）;these results implied that the cadmium-incited etiolation of the leaves was related to the deficiency of Mg and Mn in P. oleracea,but not to Fe. In sum,adding surplus S may significantly increase the content of Ca,Mg,Fe,Cu and Mn and therefore enhance PSII system in the leaves of P. oleracea under Cd stress.

Key words: sulfur, cadmium stress, Portulaca oleracea, photosynthetic characteristics, mineral element

WANG Zhu-cheng, LIU Hui, LI Rong-hua. Effects of Exogenous Sulfur on Photosynthetic Characteristics and Mineral Elements Absorption in Portulaca oleracea Under Cadmium Stress[J]. Biotechnology Bulletin, 2020, 36(3): 133-140.

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