The changes of endogenous ABA and free proline in wheat leaves exposed to 0(CK)、8 82KJ/m 2( T 1) and 12 6KJ/m 2( T 2 ) were studied. Enhanced UV B radiation led to changes of the composition of fatty acids as well as decrease of IUFA in chloroplast membrane, increase in MDA content and accumulation of ABA and proline. The analysis indicated that damage of UV B radiation to membrane system may be the reason accumulating endogenous ABA and free proline. The latter is the adaptive mechanism of pla...