Abstract:

Protective enzymes,osmotic adjustment,MDA and the protoplasmic membrane penetrability of three azalea species were studied under drought stress, and then the drought resistance was evaluated. The result showed that with the development of drought stress, the protective enzyme activities of three azalea species ascend in beginning and descend at last, except that POD activity of Rhododendron decorum was changed with a contrary trend, SOD activity of R. decorum had significant difference (P<0.05)and POD activity of R. decorum had very significant difference (P<0.01)from other two species of azalea. Osmolyte contents of the three species of azalea were increased in the beginning and decreased at last, except that the soluble sugar of R. decorum raised constantly, soluble sugar content of R. decorum had very significant difference (P<0.01)and the proline content had significant difference(P<0.05)from the other two species. There are significant difference of soluble protein between R.agastum and R. irroratum. MDA content of three species was increased first, then decreased later and increased again at the last. Relative membrane permeability of the all species were enhanced constantly, MDA content of R. decorum had very significant difference (P<0.01) from the other two species of azalea. The difference of relative membrane permeability between R. decorum and R.agastum was significant (P<0.05). The difference of relative membrane permeability between R. decorum and R. irroratum was very significant (P<0.01). A subordinate function was used to rank their drought tolerance, and the order was: R. irroratum>R.agastum>R. decorum. SOD,POD and MDA were the key indicators to evaluate the drought resistance of azalea.

Key words: azalea, drought stress, physiological response, drought resistance