PHYSIOLOGICAL MECHANISMS INVOLVED IN THE CONTROL OF LEAF WATER STATUS: IMPLICATIONS FOR THE ESTIMATION OF TREE WATER STATUS

The many factors involved in the control of leaf water potential can be separated into three classes: those affecting soil water potential, those controlling transpiration rate and those affecting the internal hydraulic resistance.
An understanding of the hydraulic flow through the soil-plant system can help to explain observations where leaf water potentials of droughted plants are higher than those of well-irrigated plants.
This effect can occur where leaf conductances and/or leaf areas have been decreased by drought to such an extent that the decreased potential drop between soil and leaf in the stressed plants (even after rewatering) can compensate for any differences in mean soil water potential that may exist.
Evidence is presented, for both field- and pot-grown plants, that g_l can be a major factor controlling _l rather than the reverse.
Analysis of data for stressed Bramley apple leaves having a higher mean _l than comparable controls, showed that the stressed plants separated into two populations: one with high _l and closed stomata (mostly showing signs of premature senescence) and one with leaf water potentials more typical of stressed plants.

I International Symposium on Water Relations in Fruit Crops

H.G. Jones

https://doi.org/10.17660/ActaHortic.1985.171.27