Stomatal density and aperture in relation to postharvest wilting in some leafy vegetables
1996
Langaoan, V.B. | Bautista, O.K. | Esguerra, E.B. | Nuevo, P.A. (Philippines Univ. Los Banos, College, Laguna (Philippines). Postharvest Horticulture Training and Research Center)
Among the leaves examined, the greatest number of stomata was observed in sweet potato leaves, followed by swamp cabbage and Malabar spinach. Jute mallow and amaranth had approximately six times less stomates than sweet potato. Stomatal density was highest at the apical portion of the leaf decreasing towards the base except for jute mallow where stomatal count was almost the same throughout the leaf. An hour after harvest, a decrease in the stomatal aperture was detected and slight wilting was apparent in all the vegetables. In 12 hours, the vegetables were already unmarketable due to wilting. There was a direct relationship between the size of the aperture and the degree of wilting. The pore of the Malabar spinach significantly decreased in size within 6 hours and had the fastest rate of closure (20.48 percent per unit change in wilting index). It thus wilted the slowest. However, the slow transpiration could also be attributed to its waxy and thick leaves. The four other vegetables had thinner leaves and were less waxy. The stomatal aperture of amaranth decreased at the fastest rate among the four vegetables and it had the least amount of stomata. It wilted at the slowest rate among the vegetables examined. Jute mallow had the lowest rate of pore closure. Although a gradual decrease in the size of the stomatal aperture was observed with time, the stomata did not close entirely even after 72 hours after harvest when the leaves were severely wilted. It shows that stomatal transpiration is significant in harvested leafy vegetables
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