Anatomical changes in persistent leaves of tissuecultured strawberry plants after removal from culture

Abstract

The anatomy and surface structure of strawberry leaves formed in vitro and after removal from culture were studied by light and scanning electron microscopy. A digital image analyzer was used to measure cell and leaf sizes. Leaves formed in vitro were relatively thin and were characterized by poorly-formed palisade cells and large air spaces. Significant deposits of epicuticular wax were observed on abaxial surfaces. After removal from culture, persistent leaves increased in size, due to increase in cell size rather than cell number. Deposits of epicuticular wax increased on both abaxial and adaxial surfaces of persistent leaves during the first 20 days after removal from culture. Leaves formed after plants were removed from culture (newly-formed leaves) were intermediate in morphology between those that matured in vitro and field-grown leaves. Palisade layers were 3–4 cells deep, and occupied a relatively greater area than palisade cells of leaves formed in vitro. Deposits of epicuticular wax became more dense and complex in newly-formed leaves, and in many cases covered stomates. Although anatomical features of persistent leaves changed after removal from culture, the changes were limited, indicating that vigorous growth of tissue-cultured plants after removal from culture depends as much on development of new leaves as on adaptation of leaves present on the plants at the time of culture.