The effects of soil and atmospheric drought on photosynthesis and stomatal control of gas exchange in three coniferous species

Abstract

1988. The effects of soil and atmospheric drought on photosynthesis and stornatal control of gas exchange in three coniferous species. -Physiol. Plant. 73: 97-104.The responses of steady-state CO, assimilation rate (A), transpiration rate (E). and stornatal conductance (&) to changes in leaf-to-air vapour pressure difference (AW) on one hand and to increasing soil drought on the other hand were examined in 2-year-old seedlings of Pseudotsuga menziesii. Pseudotsuga macrocarpa and Cedrus atlantica. Analysing the data through A vs intercellular CO, molar fraction (c,) graphs, we could determine stornatal and mesophyll contributions to changes in A as AW or soil drought were increased. Increasing soil drought affected & and mesophyll photosynthesis independently, since clearly distinct predawn leaf water potential (wp) regions appeared in which either stornatal or mesophyll effects prevailed for explaining the changes in A. The two Pseudorruga species exhibited a large vp range (between ca -0.8 and -1.5 to -1.9 MPa) in which only stomata were responsible for the decrease in A. A dramatic decline in mesophyll photosynthesis was noticed starting from values as high as -I .2 MPa (C. atlantica), -1. 5 MPa (P. macrocarpa) and -1.9 MPa (P. menziesii). Increasing AW at high soil water content led to a sharp decline in A primarily due to an alteration of mesophyll photosynthesis. Stomata1 conductance for CO, diffusion was affected in a lesser extent and in close correlation with the changes in mesophyll photosynthesis, which could suggest the existence of a functional linkage between mesophyll photosynthesis and stomata. Surprisingly, the drought resistant f? macrocarpa exhibited the least conservative water use efficiency in response to the two types of drought. In this species drought adaptation seems to be mainly due to its high root growth and soil prospection ability. Key wordr -Cedrus atlantica, drought, intercellular CO,, Pseudotsuga macrocarpa. Pseudotsuga menziesii, stornatal control, water use efficiency. , 1. M. Guehl (corresponding author) and G. Aussenac, Station de sylviculture et de production, P. Grieu

Effects of water supply on gas exchange in Pinus pinaster Ait. provenances during their first growing season

“…However, environmental conditions did not affect all the gas exchange parameters in a similar way and their evolution through time was not the same. Maximum A and E out of phase values have been also reported for three conifer species [20], suggesting a different sensitivity to pressure potential variation by stomata and mesophyll cells.…”

Ecology and ecophysiology of circum-Mediterranean firs in the context of climate change

“…There is an increasing gradient of drought resistance, ranging from A. alba, from French Mediterranean areas (Aude and Eastern Pyrenees) and probably Italian provenances which are probably better adapted to drought, especially atmospheric drought [48,50,52], than northern provenances, through to A. numidica and A. cephalonica which exhibit the best adaptation via a drought avoidance strategy.…”

Responses of photosynthesis and stomatal conductance to atmospheric humidity in some mediterranean Abies species

“…1c), thus supporting the postulate (Schulze, 1986) that alterations of leaf water status are not involved in the responses of A and g s to A w Analyzing the data in an A vs Ci graph (Fig. 1d, closed symbols) showed, as had already been found for other coniferous species (Guehl and Aussenac, 1987;Grieu et aL, 1988) (Terashima et al, 1988), was shown in the second phase of the experiment in which Aw was returned near its initial low level. During that phase, A recovered partially, with the data points remaining approximately on the same supply function (Fig.…”

“…It has been proposed (Guehl and Aussenac, 1987;Grieu et al, 1988) that decreasing C0 2 assimilation in response to increasing Aw is not only due to stomatal closure, but could be, at least partially, a consequence of altered mesophyll photosynthetic capacity. However, that interpretation is not consensual (Terashima et al, 1988 (Ci) were calculated from the gasexchange data using classical equations (see Guehl and Aussenac, 1987).…”