The effect of drought on forest water use is often estimated with models, but comprehensive models require many parameters, and simple models may not be sufficiently flexible. Many tree species, Pinus species in particular, have been shown to maintain a constant minimum leaf water potential above the critical threshold for xylem embolism during drought. In such cases, prediction of the relative...

Establishing physiological thresholds to drought-induced mortality in a range of plant species is crucial in understanding how plants respond to severe drought. Here, five common European tree species were selected (Acer campestre L., Acer pseudoplatanus L., Carpinus betulus L., Corylus avellana L. and Fraxinus excelsior L.) to study their hydraulic thresholds to mortality. Photosynthetic param...

The water status of plant leaves is dependent on both stomatal regulation and water supply from the vasculature to inner tissues. The present review addresses the multiple physiological and mechanistic facets of the latter process. Inner leaf tissues contribute to at least a third of the whole resistance to water flow within the plant. Physiological studies indicated that leaf hydraulic conduct...

Removal of the lower epidermis from a tobacco leaf allows a faster and wider range of water fluxes, without damaging the mesophyll. It also permits a more direct examination of the photosynthetic potential of the tissue at various levels of hydration.The rehydration rate of leaf discs is essentially linear. It decreases with leaf age and is correlated with the rate of dehydration, but it is ind...

Many authors have attempted to explain the adaptive response of tropical plants to drought based on studies of water relations at the leaf level. Little attention has been given to the role of the xylem system in the control of plant water requirements. To evaluate this role, we studied the hydraulic architecture and water relations parameters of two tropical canopy trees with contrasting leaf ...

We investigated how leaf hydraulic conductance (K(leaf)) of loblolly pine trees is influenced by soil nitrogen amendment (N) in stands subjected to ambient or elevated CO(2) concentrations (CO(2)(a) and CO(2)(e), respectively). We also examined how K(leaf) varies with changes in reference leaf water potential (Psi(leaf-ref)) and stomatal conductance (g(s-ref)) calculated at vapour pressure defi...

Growth-chamber studies were conducted to examine the ability of seven vegetable crops-‘Blue Lake’ bean (Phaseolus vulgaris L.), ‘Detroit Dark Red’ beet (Beta vulgaris L.), ‘Burgundy’ okra (Abelmoschus esculentus (Moench), ‘Little Marvel’ pea (Pisum sativum L.), ‘California Wonder’ bell pepper (Capsicum annuum L.), ‘New Zealand’ spinach (Spinacia oleracea L.), and ‘Beefsteak’ tomato (Lycopersico...

Desiccation of 8- to 13-day-old seedlings, achieved by withholding nutrient solution from the vermiculite root medium, caused a reduction in nitrate reductase activity of the leaf tissue. Activity declined when leaf water potentials decreased below -2 bars and was 25% of the control at a leaf water potential of -13 bars. Experiments were conducted to determine whether the decrease in nitrate re...