Abstract:

This article studied responses and resistance mechanism of Pinus massoniana to different stresses of acid rain, aluminum and acid rain-aluminum by using micronucleus test and nucleoli silver staining techniques, and the other physical or chemical methods. The results showed that: 1）Micronucleus rate of P. massoniana was gradually increased with pH lowering from 5.6 to 3.5, or aluminum concentration increasing from 100 to 3 000 mg·L^-1.The extent of impact of the different stress agents on the micronucleus rate was: acid rain-aluminum > aluminum > acid rain.　2) With pH declining or aluminum concentration increasing, number of Nucleoli of P. massoniana was gradually declined from 5.6 and 2.5 pH or from 100 to 3 000 mg·L^-1 aluminum density. The extent of impact of the different stresses on the micronucleus rate was: acid aluminum > rain-aluminum > acid rain.　3) With the stress intensifying, MDA content of seedlings increased and leaf membrane injury degrees were aggravated, at the same time the SOD and POD activities were gradually increasing, however the enzymes activities declined after a threshold of stress intensity. 4) Under the stress of acid rain-aluminum, P. massoniana was able to accumulate aluminum and tolerate aluminum poison when the pH was between 3.5 and 5.6. 5) One of the resistance mechanism of P. massoniana to aluminum poison was by increasing the synthesis of SOD and POD to reduce the aluminum toxicity with the injury. Another mechanism was by producing some substances which might be combined with aluminum to form a lower activity of the insoluble aluminum compound to reduce its mobility and activity and stored at the roots in order to reduce its poison effect.

Key words: Pinus massoniana, simulated acid rain, aluminum, heredity hurt, physiological and biochemical responses, resistant mechanisms