Hormone-induced protection of sunflower photosynthetic apparatus against copper toxicity

Abstract

The effects of excess Cu as affected by the application of exogenous hormones (gibberellic acid -GA 3 and indole-3-acetic acid -IAA) with respect to sunflower (Helianthus annuus L.) growth, physiology, and metabolism were studied. Application of 100 µM IAA lessened the toxic effects of 80 µM Cu in roots indicating greater root length and root hair formation, while addition of 100 µM GA 3 ameliorated the toxic effect mainly to the shoot. The content of photosynthetic pigments significantly declined under Cu stress, whereas application of hormones led to a substantial preservation of chlorophylls and carotenoids. 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, while application of IAA and especially GA 3 resulted in stability of the LHC of PS2 RCs. The drop in net photosynthetic (P N ) and transpiration (E) rates with preserved or slightly reduced variable to maximum fluorescence ratio (F v /F m ) in the presence of 80 µM Cu could be explained by a possible inhibition of the enzymatic processes in the Calvin cycle. Application of 100 µM IAA and 100 µM GA 3 lessened Cu effects mainly on P N . Water use efficiency was also improved under hormone exposure.

Effect of button mushroom compost on mobilization of heavy metals by sunflower

“…The effectiveness of the strain for phytoextraction was assessed with Helianthus annuus (sunflower), was known to have an ability to accmulate biomass rapidly and take up substantial amounts of metals (Turgut et al, 2004;Prapagdee et al, 2013). As reported by Ouzounidou and Ilias (2005) and El-Tayeb et al (2006), accumulation of plant biomass could be affected by excessive concentrations of heavy metals, which exert adverse impacts on growth and function of root system resulting in poor uptake of water and nutrients. As reported by Jiang et al (2008), inoculation with Burkholderia sp.…”

Phytoextraction of Heavy Metals Induced by Bioaugmentation of a Phosphate Solubilizing Bacterium

“…The effectiveness of the strain as a plant growth-promoter was assessed with Helianthus annuus, a species known to have an ability to accumulate biomass rapidly and take up substantial amounts of metals (Turgut et al, 2004;Prapagdee et al, 2013). As reported by Ouzounidou et al (2005) and El-Tayeb et al (2006), accumulation of plant biomass could be affected by excessive concentrations of heavy metals, which exert adverse impacts on growth and function of root system resulting in poor uptake of water and nutrients. As reported by Jiang et al (2008), inoculation with Burkholderia sp.…”

Repercussion of photosynthetic variables and related enzymes under influence of sodium dihydrogen orthophosphate and sodium sulphate with two modes of gibberellic acid application

“…It is, therefore, logical to include a very small quantity of P and S in scheme of GA treatments so that growth-cumdilution effect (if any due to GA application) may be compensated. Application of GA improves, among other processes, absorption and use efficiency of nutrients (Sandhya et al, 2012), activity of enzymes (Sandhya et al, 2012), cell division and cell enlargement (Buchanan et al, 2000;Taiz and Zeiger, 2010), chlorophyll content, elongation of internode (Tiwari et al, 2011;Mazid et al, 2012), membrane permeability (Taiz and Zeiger, 2010), nucleic acid and protein synthesis (Mazid et al, 2010;Tiwari et al, 2011), and transport of photosynthates (Ouzounidou and Ilias, 2005). The growth improving effect of pre-sowing seed treatment for 8h and foliar treatment at 60 and 70 DAS with 10 -6 M GA over their respective water treated control on plant height, leaf number and LA (data not published) of DCP 92-3 cultivar of chickpea grown with the recommended basal dose of N and P could be explained on the basis of its roles mentioned earlier and the fact that the supply of GA by presowing seed treatment or by foliar application would more than compensate the 'hidden hunger' of growing crops for GA.…”