[Relationship between drought resistance and endogenous hormone content in different citrus species].

Eight plant seedlings of citrus species, Citrus tangerina, C. erythrosa, C. chuana, Poncirus trifoliate, C. sinensis x P. trifoliate, C. grandis, C. sinensis and C. vessucosa were used to investigate the effects of drought stress on plant biomass, drought resistance coefficient and leaf hormone (ABA, GA1+3 , ZR, IAA) changes. The results showed that, on the condition of precipitation less than 1200 mm, the biomass of different citrus species reduced obviously, and drought-resistance index and drought resistance showed in order of C. erythrosa > C. tangerina > P. trifoliate > C. chuana > C. sinensis x P. trifoliate > C. grandis > C. sinensis > C. vessucosa. The leaf ABA contents of the eight species increased whereas GA1+3 , ZR and IAA decreased, under the condition of drought stress. The ratios of ABA/GA1+3 and ABA/ZR in the species of C. erythrosa and C. tangerina increased drastically, yet there was no significant correlation between the ratio of ABA/IAA and the drought tolerance. The drought-resistance index was significantly positively related to the relative content of ABA (P < 0.01), while significantly negatively related to the relative content of GA1+3. The function to enhance drought resistance by those endogenous hormones in the citrus species showed in order of ABA > GA1+3, ZR > IAA.