Quantification of lenticels in Japanese plum cultivars and their effect on total fruit peel permeance

Abstract

Fruit peel vapour permeance is an indicator of the propensity of fruit to lose moisture. Permeance is affected by cuticle composition, as well as stomata, lenticels and cracks in the cuticle. Stomata play a significant role in controlling the transpiration of leaves. Since lenticels on fruit often form from non-functional stomata, this study determined whether lenticels contribute to peel permeability in Japanese plums and whether this varies between cultivars. In 2015/16 as well as 2016/17, ‘Laetitia’ and ‘Songold’ were investigated and in 2016/17, ‘African Delight™’ and ‘Sapphire’ were added to the study. Fruit were sampled from three weeks before commercial harvest until the commercial harvest date. On each sampling date, the peel permeability of individual fruit was determined and the number of open lenticels quantified. Lenticel numbers and peel permeability of fruit both differed significantly between fruit of different cultivars and between seasons. Significant correlations between permeability and the number of open lenticels were found only in ‘Songold’, ‘African Delight™’, and ‘Sapphire’ fruit. The percentage of open lenticels are therefore not the determining factor of total fruit peel permeability or the tendency of plums to lose moisture. Cuticle composition seems to play a more important role in determining fruit moisture loss.