Deoxyribonucleic acid-protein (DNAP) of the cell nucleus was purified from developing wheat (Triticum aestivum L.) embryo cells under drought stress, with two cultivars differing in drought tolerance as experimental materials - Longmai No. 079 (drought-tolerant) and Wanmai No. 52 (drought-sensitive). Levels of polyamines (PAs) non-covalently conjugated to the DNA and covalently conjugated to the proteins of DNAP were detected. After soil drought treatment for 10 days, in drought-tolerant Longmai No. 079, the increases in the levels of spermine and spermidine non-covalently conjugated to DNA of DNAP were more statistically significant (P<0.05) than in drought-sensitive Wanmai No. 52. Treatment of Wanmai No. 52 with exogenous Spm could not only enhance the tolerance of the cultivar to drought stress, as judged by flag leaf water content, plasma membrane permeability and grain growth, but also elevate the levels of spermine and spermidine noncovalently conjugated to the DNA of the cultivar. On the contrary, treatment of Longmai No. 079 with methylglyoxyl-bis guanylhydrazone, an inhibitor of S-adenosylmethionine decarboxylase, could significantly (P<0.05) aggravate the drought stress to this cultivar, accompanied by a marked decreases in the levels of spermine and spermidine non-covalently conjugated to the DNA of the cultivar. On the other hand, the content of putrescine covalently conjugated to the proteins of DNAP rose more markedly (P<0.05) in Longmai No. 079 than in Wanmai No. 52. The transglutaminase inhibitor, o-phenanthrolin, could markedly reduce the drought-induced increase in the level of putrescine covalently conjugated to the proteins of DNAP and aggravate drought stress to the two cultivars. Collectively, it could be inferred that spermine and spermidine non-covalently conjugated to the DNA and putrescine covalently conjugated to the proteins of DNAP in the developing grain embryo cell nucleus might enhance the tolerance of wheat plants to soil drought.