Observation on pH variation during cell wall acid degradation in Camptotheca acuminata leaf under the tissue culture condition Phenolic acid degradation fungi screened from successive plantation site of Chinese fir Possible mechanism involved with isolation protoplast of leaf Light microscopic observation of acid degradation on cell coat system of Arabidopsis thaliana leaves Influence of acid culture medium on cell wall degradation of Camptotheca acuminata leaves Possible mechanisms involved with the formation of leaf callus