Abstract:

The changes in contents and forms of polyamines (PAs) in seedling leaves of two maize (Zea mays L.) cultivars, Nongda 108 (drought-tolerant) and Yedan 13 (drought-sensitive), were investigated under osmotic stress. On the 8th day after polyethylene glycol (PEG) -6 000 treatment, free spermidine (fSpd) and free spermine (fSpm) content in leaves increased significantly（P＜0.05）in Nongda 108, while Yedan 13 showed a significant increase of free putrescine (fPut) content. Thus Nongda 108 gave a higher ratio of (fSpd + fSpm)/fPut than Yedan 13 in leaves under osmotic stress. Exogenous methylglyoxal-bis (guanylhydrazone) (MGBG), which is a S-adenosylmethionine decarboxylase (SAMDC) inhibitor, resulted in reduction of fSpd and fSpm contents and aggravation of PEG-induced injury to Nongda 108 leaves, while exogenous Spd treatment resulted in an increase of fSpd + fSpm in leaves, in concert with an alleviation of PEG-induced injury to seedlings of Yedan 13. Osmotic stress induced significant increases of acid soluble conjugated PA (AS-conjugated PA) and acid insoluble bound PA (AIS-bound PA) contents in leaves of Nongda 108, and osmotic stress affected slightly in Yedan 13 leaves. Exogenous phenanthrolin (o-Phen), an inhibitor of transglutaminase (TGase), aggravated PEG-induced injury to Nongda 108, coupled with decreases of AIS-bound PA content. The results suggest that fSpd, fSpm, AS-conjugated-PA and AIS-bound PA facilitate the osmotic stress tolerance of maize seedlings.

Key words: Maize, Polyamine forms, Osmotic stress