Smoke-water, karrikinolide and gibberellic acid stimulate growth in bean and maize seedlings by efficient starch mobilization and suppression of oxidative stress
2016
Sunmonu, T.O. | Kulkarni, M.G. | Van Staden, J.
Exposure of seeds to optimum concentrations of smoke-water, karrikinolide and gibberellic acid promotes germination in many plants. The present study investigated the possible mechanism by which this is achieved. The activities of some hydrolytic enzymes (amylase, invertase and protease) as well as antioxidant enzymes (peroxidase, superoxide dismutase and catalase) were assayed in relation to nutrient accumulation in bean (Phaseolus vulgaris L.) and maize (Zea mays L.) seedlings using these three plant growth promoting substances (PGPS). The PGPS caused lipid peroxidation in the bean cotyledons and maize endosperm as evidenced by an increased malondialdehyde (MDA) concentration and antioxidant enzyme activity. This was accompanied by a reduction in starch content and amylase activity. However, a reverse trend was observed in bean shoots and roots and maize coleoptiles and roots, probably accounting for the observed increase in growth recorded in these seedling parts. In contrast, the PGPS had no effect on protein content, suggesting that this reserve was not mobilized during the period under study. These results suggest that the probable mechanism by which smoke-water, karrikinolide and gibberellic acid promote seedling growth may be through efficient mobilization of starch reserves and subsequent transport to other seedling parts and by suppression of oxidative stress.
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