The effects of water stress on gas-exchange in Pinus brutia, var eldarica

Abstract

Pinus brutia var. eldarica is often considered to possess photosynthetic characteristics that make it highly tolerant to drought conditions. However, very little is known about it's photosynthetic response to water stress under either laboratory or field imposed drought conditions. The purpose of this study was to utilize laboratory gas-exchange measurements to determine the effects of water stress and recovery from stress on photosynthetic capacity of potted Pinus brutia via. eldarica plants. Analysis of the rate assimilation (A) versus intercellular CO₂ (Cᵢ) data indicates that recovery of carboxylation efficiency (g'm) (i.e. Rubisco activity and amount) does occur after daily re-watering of moderately stressed (ψ₂ ≃ -2.0 MPa) Pinus brutia. However, these same data indicate that irreversible damage to cell membranes results in an inability to re-generate RubP. Although inferences on the effect of stress on A in field grown Pinus brutia is tenuous, these laboratory results indicate that Pinus brutia may not be as drought tolerant as commonly believed.