The Effects Of Environmentalstresses On The Compont And Gene Expression Of Flovoinds In Trifoliate Orange

Citrus are usually subjected to environmental stresses such as low temperature, salt and drought et al., which adversely affect the citrus gtowth and yield in China. Flavonoids are one of the most important secondary metabolites, which protect plant tissues against kinds of oxidative damages. In order to investigate the resposes of flavonoid metabolism to environmental stresses, contents of total flavonoids and three individuals, as well as expression of six corresponding genes in the biosynthetic pathway of flavoinds, were examined in trifoliate orange (Poncirus trifoliate) seedlings under low temperature, salt and drought stresses. Main results are as follows.1. The relative membrane permeability, MDA concentrations and POD activities in trifoliate seedlings increased during the low temperature treatment. In roots, contents of total flavonoids went up to the highest at 24 h under the low temperature, followed by a continuous decline with increases in the treatment duration, while in leaves the contens of total flavonoids evidently decreased at 24 h and further to the highest at 48 h. Changes in the contents of Naringenin, Naringin and Hesperidin in leaves and roots were similar to the total flavonoids, which increased firstly and then diclined in treatment duration, but which clearly increased in the roots. Changes in gene expression of CHS, CHI, F3H, FLS, DFR and ANS were similar to the total flavonoids.Expression of there 6 gene obviously increased at 48 h under low temperature, but in the highest expression levels of CHS and CHI were at 24 h and that of F3H were at 12 h under low temperature, while expression levels of FLS, DFR and ANS were highest at 12 h and then down-regulated thereafter.2. The relative membrane permeability, MDA concentrations and POD activities in trifoliate seedlings increased as NaCl concentration increased. The leaves and roots were damaged clearly when the NaCl concentration≥160 mmol·L-1. The contents of total flavonoids in roots and leaves increased after treatment, and the highest content was at 80 mmol·L-1 and at 240 mmol·L-1. The contens of Naringenin, Naringin and Hesperidin in leaves and roots increased under different concentration of salt stress, except the contents of Naringenin in leaveas and the Naringin in roots at 160 mmol·L-1. The changes of gene expression of CHS, CHI, F3H, FLS, DFR and ANS were similar to the total flavonoids, which were up-regulated under different soult stresses in leaveas and roots.3. The relative membrane permeability, MDA concentrations and POD activities in trifoliate seedlings increased with the continuance of drought stress and began to decrease after re-watering. The contents of total flavonoids in both leaveas and roots increased to the highest at 6 d in drought stress and the induced with the following treatment. Changes of the contents of Naringenin, Naringin and Hesperidin both in leaves and roots were similar to the tatol flavonoid. Changes of expression of CHS, CHI, F3H, FLS, DFR and ANS were up-regulated with the increasing of drought level, including the expression of CHI, F3H and ANS were highest at the 6 d and that of CHS, FLS and DFR were highest at the 9 d in drought stress.