Abstract: 【Objective】Drought, a serious problem existed in agricultural production, is one of the most important factors limiting agricultural growth and further expanding the crops acreage. Study of the mechanism of plant drought resistance will provide an important safeguard for the increase of agricultural production and incomes. Phytohormone plays a significant role in plant resistance to water deficiency. Based on this study we may further understand the function of phytohormone in plants in response to drought stress, and provide a theoretical basis for the regulation of plant hormone in the production and cultivation of crop in arid regions.【Method】With wheat variety Lumai No.21 as material, immunohistochemical localization was used to investigate the distribution of endogenous hormones ABA and IAA in wheat organs（root, leaf sheath and leaf blade）under drought-stress. While an indirect competitive enzyme-linked immunosorbent assay (icELISA) was applied to quantitate the content changes of ABA and IAA in wheat organs. The chemical signal intensity of the immunohistochemical localization and the endogenous hormone concentration of the icELISA were compared for confirming the effect of the results.【Result】Four weeks after drought treatment with weighing method, the wheat in control group (CK) grew uprightly, leaves were healthy and green, and the whole plant grew well. Wheat in drought treatment group (ND) grew small, leaves areas were reduced and had different degrees of wilting and yellowing phenomenon. Immunohistochemical localization was used to investigate the distribution of endogenous hormones ABA and IAA in wheat organs. The results showed that, the intensity of the staining of ABA in drought-stress wheat organs was stronger than that in wheat of control group, and that the leaf was most noticeable, especially in stomata guard cells and vascular bundle tissue, then was the leaf sheath. Similar results in IAA were obtained, but it was not as noticeable as ABA. An icELISA was applied to quantitate the content changes of ABA and IAA. The result of immunohistochemical localization above is in accord with the result of icELISA. The ABA content in the root was 61.51 ng•g-1 FW, 2.82 times that of controls (21.8 ng•g-1 FW). The ABA content in leaf sheath was larger, 175.35 ng?g-1 FW, 3.65 times that of controls (48.02 ng•g-1 FW). The largest rise of ABA content (512.12 ng•g-1 FW) was in leaves, 10.16 times significantly higher than controls (50.42 ng•g-1 FW). Variance analysis showed that the ABA contents in wheat seedling root, leaf sheath and leaf were significantly different (P＜0.01) under drought stress and normal water supply. The contents of IAA in wheat seedling root, leaf sheath, leaf were 72.81, 274.46 and 195.75 ng•g-1 FW under the normal water supply, respectively. The contents of IAA under water stress condition increased but not very much, and they were 123.56, 400.48 and 417.30 ng•g-1 FW, respectively. Significant analysis (t test) showed that the difference of IAA content in wheat seedling roots under drought stress and normal water supply condition was not significant (P＞0.05), but the difference of IAA content in leaf and leaf sheath was extremely significant (P＜0.01). 【Conclusion】The contents of ABA and IAA tended to increase in the organs of wheat when subjected to water deficiency, and the level of ABA increased obviously, while that of IAA increased gently compared with ABA. The trend of the coordination between ABA and IAA is to cause stomatal closure, promote root growth and slow the growth rate to effectively protect against drought damage.

Key words: drought-stress , wheat , abscisic acid , indoleacetic acid , immunohistochemistry localization