EFFECT OF CERTAIN NUTRIENT DEFICIENCIES ON STOMATAL BEHAVIOR

Abstract

Although a great deal of research has been done on stomata, nevertheless, the facts regarding these important plant structures are still fragmentary and there are differences of opinion as to their fundamental characteristics. In 1895 Blackman (3) demonstrated the importance of stomata in gaseous exchange, although the possible relations of stomata to transpiration had long been recognized. Regarding the regulatory role of stomata in respect to transpiration, differences of opinion exist. That the stomata open and close periodically during twenty-four hours has been established. Various theories have been advanced concerning the mechanism of opening and closure and the cellular changes associated with these. According to some, the changes of starch to sugar and vice versa with consequent changes in osmotic relations are responsible for the opening and closure. Scarth (31), in recent years, has emphasized the importance of changes in the pH of the guard-cell vacuome due to changes in carbon dioxide content of the leaf, the opening and closure of the stomata being dependent directly or otherwise upon the effects of pH on starch-sugar changes or protein hydration, or both. Whatever eventually may be found to be the actual mechanism involved in the opening and closure of stomata, it is clear that the metabolism of the guard cells and the adjacent tissues must also be involved. While much attention has been given to the direct influence of light, of leaf water content, and of chemical reagents and reactions on stomatal behavior, no attention, except for the work of Pleasants (27), has been given to the part played by nutrients on stomatal behavior. There has been some work reported on the effect of nutrient deficiency on the rate of photosynthesis and respiration by Gruzit and Hibbard (11), Briggs (4), Lyon (20, 21), Gregory and Richards (8), and others. Since stomatal behavior through its effects on the loss of water and gaseous exchange may markedly influence plant behavior, a fuller knowledge of the effect of various factors on stomatal behavior is desirable. Of the factors that are of importance, theoretically and practically, that of mineral nutrient supply may be of considerable significance.