Advances of explant browning in plant tissue culture

Explant browning is the main obstacle in plant tissue culture.At present,the primary factors causing explant browning are explant materials,pH value,the culture conditions,the ingredients,the states and the ragidities of culture medium.There are some methods preventing explant browning such as perfect explant and culture conditions,cell filtration and materials pretreatment,adding inhibitors or sorbents to culture medium and so on.There are three hypotheses about the mechanism of explant browning:phenol and phenolic-enzyme regional distribution hypothesis,free-radical damage hy-pothesis and protective enzyme system hypothesis.