Studies of stomatal distribution on the leaves of four apple varieties

SummaryA scanning electron microscope was used for monthly studies of the stomatal distribution on the leaves of four apple varieties (Cox’s Orange Pippin, Lord Lambourne, Golden Delicious and Egremont Russet) throughout the 1972 growing season. There was considerable variation over the surface of single leaves and between leaves of the same variety, and few definite trends could be discerned apart from an early season increase in the numbers of functional stomata. Cox’s Orange Pippin leaves had significantly more stomata per unit area than Golden Delicious leaves, but other varietal differences were not consistently significant. It was concluded that Golden Delicious leaves may be better adapted to conserve water than Cox leaves because of their stomatal density. The stomata on leaves of meadow orchard trees apparently developed to full maturity more quickly than those of hedgerow orchard trees.