Alleviation of Thermoinhibition in Chickpea Seeds by Putrescine Involves the Ethylene Pathway
Germination of chickpea (Cicer arietinum L.) was inhibited by supraoptimal temperatures of 30 or 35�C, 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 30�C. 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).