Involvement of polyamines in the contrasting sensitivity of chickpea (Cicer arietinum L.) and soybean (Glycine max (L.) Merrill.) to water deficit stress

Chickpea (Cicer arietinum L. cv. GPF2) and soybean (Glycine max (L.) Merrill cv. Brag) genotypes were subjected to varying water stress levels of -0.2 to -0.8 MPa to assess their relative sensitivity towards water stress. Soybean seedlings experienced significantly more stress injury (as electrolyte leakage) than chickpea at all stress levels. LD 50 in terms of percent germination, root length, and root growth rate occurred at -0.4 MPa in soybean and at -0.6 MPa in chickpea. In chickpea, the root water content was higher than in soybean during stress. Endogenous levels of individual as well as total polyamines (PAs) in roots of 7-d-old seedlings subjected to -0.8 MPa stress increased to a significantly greater extent in chickpea than in soybean. The stress injury was accentuated as the PA levels declined in both the plant types. The reduced levels of PAs in soybean, especially putrescine (PUT) and spermidine (SPD) relative to chickpea, were related to higher stress injury and decreased water content. Exogenous PUT and SPD markedly mitigated the stress-induced effects, particularly in soybean. Inhibitor studies involving α-Difluromethylarginine (DFMA) and α-difluromethylornithine (DFMO), the biosynthetic inhibitors of PUT, as well as cyclohexylamine (CHA), biosynthetic inhibitor of SPD and SPM, corroborated the role of PAs in mediating the differential sensitivity of chickpea and soybean to water stress.