Salicylic Acid Ameliorates Germination, Seedling Growth, Phytohormone and Enzymes Activity in Bean (Phaseolus vulgaris L.) under Cold Stress

Abstract

An experiment was carried out under laboratory condition to tackle low temperature stress by using salicylic acid (SA). Seeds of six common bean varieties (Polista, Nebraska, Goro, Helda, Duel and Giza 6) were soaked in water or 10 −4 M aerated solution of salicylic acid (SA) for 6 h. Treated and untreated seeds were germinated at 25 ○ C (optimal temperature) and at 15 ○ C (suboptimal temperature or chilling stress) under dark controlled conditions for 9 and 30 days , respectively. Germination and seedling growth of the six tested varieties were significantly hindered under low temperature. Seed treatments with SA significantly improved germination percentage, germination rate and seedling criteria, compared with control seeds under optimal and low temperature stress conditions. The content of Indolacetic acid (IAA), Gibberellic acid (GA3) and Abscisic acid (ABA) increased in the different varieties under study, in response to seed soaking in 10 −4 M SA at 15°C. GA3/ABA ratio showed maximum increase in Duel and Helda, while the lowest ratio was observed in Giza 6 and Nebraska seedlings. At the same low temperature, catalase activity was decreased, whereas that of polyphenol oxidase increased on using 10 -4 M SA. Peroxidase isozymes indicated five to three isozymes in seedlings of the six bean varieties. Salicylic acid treatment resulted in detecting (in Duel) and disappearance (in Nebraska) of peroxidase isozymes at Rf: 0.37, which might be responsible for tolerance and sensitivity mechanism, respectively. The present results indicated that, salicylic acid stimulated various growth aspects of bean seedlings perhaps through interference with the enzymatic activities responsible for biosynthesis and/or catabolism of growth promoting and inhibiting substances. Thus, it might be concluded that, SA could eliminate the adverse effects of cold stress in common bean. (Journal of American Science 2010;6(10):675-683). (ISSN: 1545-1003).