Isolation of apple leaf protoplasts

In order to make genetic manipulation accessible to fruit-trees, it was necessary to solve the problem how to isolate protoplasts. Cell wall digestion performed with commercially available, digestive enzymes was not applicable to apple leaf cells. No mixture of digestive enzymes gave more than single protoplasts from any part of the plant, but very often the cells were damaged. Therefore, the authors tried to change the plant tissue by altering the growth conditions of the shoots.