Causes and Control of Vitrification on the Plantlets of Woody Plants

Vitrification is a physiological disease change under the noninjured stress conditions. The efficiency of the rapid micropropagation is severely affected by hyperhydricity during in vitro culture. It was indicated by the review of relevant literature both at home and abroad that the formation of vitrification in testtube plantlets of woody plant tissue culture was related to a serial of factors such as the concentration of sucrose (carbon source) in the medium, the varieties and concentration of agar, ion content (mainly for Cu2+), cytokinins, ethylene and auxin. The release control of ethylene by peroxidase-IAA oxidase system, the lignification inhibition by the decrease of phenylalanine ammonialyase (PAL) and acidic peroxidase activity, lack of cellulose and lignin, reduction of the wall pressure could all cause excessive water absorption of the cells, which could result in vitrification of woody plantlets. The main domestic and international techniques to control the vitrification included to increase agar concentration and sugar content in the medium, to reduce the ion concentration (Cl-, NH4+) and the concentration of Cytokinins, or to add phloroglucinol or phlorizin to the medium. The explant materials should be treated under low temperature and the environmental relative humidity should be reduced.