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THE INFLUENCE OF LIGHT AND WATER DEFICIT UPON DIFFUSIVE RESISTANCE OF LEAVES OF VICIA FABA L.
Author(s) -
KASSAM A. H.
Publication year - 1973
Publication title -
new phytologist
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.742
H-Index - 244
eISSN - 1469-8137
pISSN - 0028-646X
DOI - 10.1111/j.1469-8137.1973.tb04407.x
Subject(s) - vicia faba , stomatal density , light intensity , horticulture , chemistry , vapour pressure deficit , diffusion , botany , biology , transpiration , photosynthesis , physics , optics , thermodynamics
SUMMARY The resistance of the upper ( r u ) and lower ( r 1 ,) surface of the leaf to diffusion of water vapour in Vicia faba was influenced differently by light and water deficit. r u saturated at about 100 Wm ‐2 while r 1 , saturated at about 13 Wm ‐2 . At a given light intensity r 1 , was always smaller than r 1 . The difference in the density of stomata between the two surfaces of the leaf alone does not explain the magnitude of the difference between r u and r 1 , for V. faba and other species. Impressions of the stomata of the two surfaces at different light intensities indicated that the stomata on the lower surface were more widely open than those of the upper surface. When stomatal response to light was not saturated, increase in leaf‐water deficit was accompanied by increase in r a and r 1 . Under saturating light intensities however r 1 , increase in leaf‐water deficit did not affect r u and r 1 , until leaves were flaccid and pressure potential close to zero; although the stomata on the upper surface closed at slightly higher water potentials than those of the lower surface. A dry treatment lasting 2 days, at the end of which the leaf was flaccid, affected the subsequent performance of the stomata while the leaf‐water deficit had been eliminated. This after‐effect was much greater on r u than on r 1 , and a complete recovery of the stomata on the upper surface took more than 2 days. Larger differences between r u and r 1 , values are associated with larger lower to upper stomatal density ratios in a number of species. However r 1 , the ratios of r u / r 1 , are much larger than the corresponding stomatal density ratios. It appears that in V. faba , and in a number of other species, the stomata of the lower surface are more widely open that those of the upper surface either at equal light intensity or when leaves are illuminated from above.