Regulation of stomatal aperture in response to drought stress mediating with polyamines, nitric oxide synthase and hydrogen peroxide in L.

To assess the role of genes involved in polyamines synthesis, nitric oxide synthase (NOS), copper amine oxidase activity (CuAO) and hydrogen peroxide (HO) in regulation of stomatal aperture to drought stress in L., a study was performed at three irrigating levels (25%, 50%, and 100% field capacity) with three replications at 1, 3, 6 and 12 days. The results showed that putrescine (Put) accumulation occurred under both 50% and 25% FC at 1 d. Furthermore, the role of the Put direct biosynthesis pathway ornithine decarboxylase (ODC) was more effective under 50% FC whereas in the 25% FC the Put indirect production pathway (agmatine iminohydrolase (AIH), N-carbamoyl putrescine amidohydrolase (CPA) and arginine decarboxylase (ADC)) was more effective. HPLC results showed that the accumulation of spermidine (Spd) and spermine (Spm) is consistent with the expression of ( () and () genes. Spd accumulation under both 50% and 25% FC occurred on the 3 d and then decreased in the other days. Spm content showed an increasing trend from 6 d under 50% FC and from 3 d under 25% FC. Our results suggest that among the measured polyamines, Put oxidation through CuAO activity increased resulted in an increase in HO production. The HO accumulation also as a secondary messenger led to enhance in gene expression. Increase in gene expression can act as a signal resulting in stomatal closure.