Alleviation of Thermoinhibition in Chickpea Seeds by Putrescine Involves the Ethylene Pathway

Abstract

Germination of chickpea (Cicer arietinum L.) was inhibited by supraoptimal temperatures of 30 or 35ºC, but the inhibition was alleviated by a relatively low concentration (1 mM) of putrescine (Put). This allevation may be due to (a) stimulation of the 1-aminocyclopropane-1-carboxylate (ACC) synthase and ACC oxidase activities; (b) increased levels of ACC and decreased levels of 1-(malonylamino)cyclopropane-1-carboxylic acid (MACC); or (c) strongly increased ethylene production. Put at 10 mM did not alleviate thermoinhibition, although, as with Put at 1 mM, it did inhibit adenosyl-methionine (AdoMet) decarboxylase. Alleviation conditions resulted in: (a) an induced accumulation of free Put (S) and Put conjugated to substances of low (HS) and high (HP) molecular weight; (b) a decrease in spermidine (Spd) and spermine (Spm) (S and HP); and (c) no alteration in the levels of Spd and Spm (HS) with respect to the absence of Put (1 mM) at 30ºC. In the presence of Put (10 mM), increased accumulation of Put (S, HS and HP) was detected, but with a sharp decrease of Spd and Spm (S and HS).