Biophysical Adaptations of Four Western Conifers to Habitat Water Conditions

Abstract

Various properties associated with plant water economy, including osmotic potential at incipient plasmolysis (.pi.0), elastic modulus (e) and maximum potential stomatal conductances were measured in Pinus ponderosa, Pseudotsuga menziesii, Abies grandis and Thuja plicata growing in northern Idaho to determine the role of such features in adaptation. Pinus and Pseudotsuga exhibited the lowest .pi.0 while Thuja had the highest. Similarly, Pinus and Pseudotsuga exhibited the greatest amount of acclimation relative to this feature and Thuja the least. The proportion of apoplastic water between full turgidity and incipient plasmolysis was highest in Thuja, intermediate and about equal in Pinus and Pseudotsuga, and lowest in Abies. Maximum potential stomatal conductance was 8-fold greater for Pinus than for Abies, which had somewhat greater conductance than Pseudotsuga; Thuja had the lowest potential conductance. Overall, there was a strong correspondence between the properties investigated and the habitat preference of the respective species, suggesting that these properties have adaptive significance in such plants.