Casein hydrolysates can be a source of calcium, phosphate, several microelements, vitaminsand most importantly, a mixture of up to 18 aminoacids. Several casein hydrolysates are availablecommercially but their value for plant tissue culturecan vary considerably. Acid hydrolysis can denaturesome amino acids and so products prepared byenzymatic hydrolysis are to be preferred. The bestcan be excellent sources of reduced nitrogen, as theycan contain a relatively large amount of glutamine.Casein hydrolysate overcomes the shortage of glutamine when there is insufficient phosphorus for adequate biosynthesis however several investigatorshave concluded that casein hydrolysate itself is moreeffective for plant culture than the addition of themajor amino acids. This has led to speculation thatcasein hydrolysates might contain some unknowngrowth promoting factor (George
et al
2008).