Differential Responses of Onion and Garlic Against Plant Growth Regulators (original) (raw)
The effects of Gibberellic acid-GA 3 , Prohexadione-Calcium, and Ethephon pre-harvest application on yield, biomass production, photosynthetic function, lipid peroxidation and quality characteristics of onion (Allium cepa L.) and garlic (Allium sativum L.) plants were investigated. Shoot length and biomass of onion and garlic, expressed either in fresh or dry weight, increased significantly under GA 3 , while a progressive decrease under Prohex-Ca and Ethephon occurred. Higher MDA (lipid peroxidation) values were recorded after Prohex-Ca and Ethephon supply on onion and garlic plants; it seems that GA 3 treatment prevents lipid peroxidation as measured with the help of the TBARS method. Plants treated with Prohex-Ca and Ethephon revealed higher peroxidase activity compared to control and GA 3 treated plants. Considering the results of MDA content and peroxidase activities it can be assumed that GA 3 treated plants are slightly protected from the natural course of oxidative stress, which occurs during ageing as observed for control samples. The fluctuations of chlorophyll fluorescence parameters represent a general decline in chloroplasts function after plant growth regulators exposure, whereas in combination to the suppressed chlorophyll content, structural malformations of photosystems may also occur. The production of ascorbic acid, glucose and fructose content seems to be enhanced under GA 3 in both species, while their values were depressed under Prohex-Ca and Ethephon. Overall, only GA 3 supply leads to a vigorous onion and garlic growth and yield.
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