Experimental Studies of the Factors Controlling Transpiration
| Autor: | E. J. Spencer, F. L. Milthorpe |
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| Rok vydání: | 1957 |
| Předmět: | |
| Zdroj: | Journal of Experimental Botany. 8:413-437 |
| ISSN: | 1460-2431 0022-0957 |
| DOI: | 10.1093/jxb/8.3.413 |
| Popis: | SUMMARY Transpiration rates of single leaves of Pelargonium and wheat were measured under constant conditions of light, temperature, and air flow. Concurrently, stomatal movement was followed with the resistance porometer during cycles of changing water content of the leaf and changes induced by light and darkness. Stomatal movement was found to exert a large controlling influence on the transpiration rate, whereas water content had an extremely small or negligible effect. An approximately inverse linear relation between transpiration rate and logarithm of resistance to viscous flow through the leaf is believed to be the resultant of an inverse curvilinear relationship between the diffusive conductance of the stomata and log. leaf resistance and the decreasing difference of vapour pressure arising from the higher transpiration rates with increasing stomatal conductances. Nevertheless, the relation demonstrates that the transpiration rate is influenced by the degree of stomatal opening throughout its entire range. There was some evidence of lower transpiration rates during and after recovery from wilting than before wilting. This is attributed to a decrease in a cell-wall conductance, the evaporating surface being located within the cell wall. During wilting partially irreversible contraction of the cell wall occurs. There was also evidence of slow changes in cell volume at full turgidity attributable to plastic flow. These occurred when the leaf was transferred from environments of a high to low potential for evaporation. Extensive movement of the stomata followed changes in leaf water, passive opening resulting from decrease and closure from increase of leaf water. It is suggested that the direction and extent of stomatal changes induced by water deficits is a consequence of the rate of change of leaf water content and not of the absolute values. The stomata also showed an enhanced tendency to close in dry moving air following a period of wilting even after the leaf had regained turgidity. |
| Databáze: | OpenAIRE |
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