Hormone-induced protection of sunflower photosynthetic apparatus against copper toxicity
Ouzounidou, G.(National Agricultural Research Foundation, Lycovrissi (Greece). Inst. of Food Technology)E-mail:[email protected] | Ilias, I.(Technological Educational Inst. of Thessaloniki, Sindos (Greece). Dept. of Plant Production)
The effects of excess Cu as affected by the application of exogenous hormones (gibberellic acid - GA3 and indole-3-acetic acid - IAA) with respect to sunflower growth, physiology, and metabolism were studied. Application of 100 M IAA lessened the toxic effects of 80 M Cu in roots. The content of photosynthetic pigments significantly declined under Cu stress, whereas application of hormones led to their preservation. Under Cu stress, the rate constant of energy trapping by photosystem 2 (PS2) reaction centres (RCs) was reduced as a result of physical dissociation of the light-harvesting complex (LHC) from PS2 core, whereas application of IAA and especially GA3 resulted in stability of the LHC of PS2 RCs. Application of 100 M IAA and 100 M GA3 lessened Cu effects on net photosynthetic rate. Water use efficiency was also improved under hormone exposure.
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