Daily Changes in Stomatal Aperture and in Carbohydrates and Malate Within Epidermis and Mesophyll of leaves of Commelina Cyanea and Vicia Faba

Abstract

Stomatal apertures and methanol-, water-, and hydrochloric acid-soluble carbohydrates and malate were measured in the epidermis, mesophyll, and midvein of leaves of C. cyanea R. Br. and V. [aba L. over a period of 26 hr in one experiment and over 9 hr during the photoperiod in a second experiment.Metabolite concentrations were the same in mesophyll and vein and followed typical diurnal patterns of accumulation and depletion. Concentrations in the epidermis showed little association with those in the mesophyll. The accumulation during the morning of epidermal sugars plus malate, at rates equivalent to 1·4 and 3 . 6 p.g mg-1 hr-1 in C. cyanea and V. [aba, was accompanied by a fall in polysaccharides with no net change in total metabolites, whereas rises in mesophyll sugars and malate of 3·6 and 6'9 p.g mg-1 hr-1 were associated with increases in polysaccharides.Associations were found between aperture and the concentration of epidermal malate.The differences between minimum and maximum epidermal malate concentrations (about 2· 6 and 6·1 p.g mg-1 in C. cyanea and V. [aba) were sufficient to balance the potassium changes found by other authors to occur during stomatal opening in Vicia.

Sucrose: a solute that accumulates in the guard‐cell apoplast and guard‐cell symplast of open stomata

“…Although he found a strong relationship between time of day and 'guard cell' sucrose content, the relationship between aperture and sucrose content was weak (r ~ = 0.46 for Vicia and r 2 = 0.29 for Commelina). The experimental approach of Outlaw and Manchester [12] was different from Pearson's approach [23] and also provides results that complement those presented here. These workers [12] made a technically unambiguous measurement of guard-cell-sucrose content of stomata that were stimulated to open under non-photosynthetic conditions.…”

“…Notwithstanding, the values obtained with peels over the course of a day should be relative and represent maximum limits when calculated to a guard-cell basis. Given these reservations, the most detailed published investigation to date of sucrose contents of 'guard cells' over a daily cycle [23] provides a reference for comparison. In brief, Pearson [23], who assayed for sucrose in unwashed epidermal peels of Vicia faba and Commelina communis, found a consistent increase, which peaked midafternoon (ca.…”

“…Given these reservations, the most detailed published investigation to date of sucrose contents of 'guard cells' over a daily cycle [23] provides a reference for comparison. In brief, Pearson [23], who assayed for sucrose in unwashed epidermal peels of Vicia faba and Commelina communis, found a consistent increase, which peaked midafternoon (ca. 1,350 fmol.guard-cell-pair -1, according to our conversion of his data to a basis comparable to ours).…”

Light Quality and Osmoregulation in Vicia Guard Cells

“…Measurements of K+ content in Commelina guard cells with ionsensitive electrodes have also shown discrepancies between K+ concentrations and measured osmotic potentials, leading to the suggestion that sucrose could be an additional source of osmoticum (18). Increases in sugars have also been correlated with opening in experiments with epidermal peels (29,31). Both import of sugars from the mesophyll (3,25,26) and starch interconversion (40) have been invoked as sources for the osmotically active sugars.…”

Elevated Levels of Both Sucrose-Phosphate Synthase and Sucrose Synthase in Vicia Guard Cells Indicate Cell-Specific Carbohydrate Interconversions

“…Mouravieff, 1972) and quantitative techniques (Outlaw and Manchester, 1979), constitutes evidente for a pathway leading to the accumulation of malate, a counter ion to K+ (Raschke, 1979;Outlaw, 1982). Notwithstanding, there remain (a) the continuous history of reports (Pearson, 1973;Outlaw and Manchester, 1979; unpublished data cited by Outlaw, 1982;Reddy and Rama Das, 1986;Poffenroth et al, 1992) of a positive correlation between guard-cell sugar content and stomatal aperture size, and (b) Supported in part by a grant from the U.S. National Science Foundation to W.H.O. and and Lettau, 1980aand Lettau, , 1980b.…”