Water-use efficiency in cork oak (Quercus suber) is modified by the interaction of water and light availabilities

Abstract

We studied the interaction of light and water on water-use efficiency in cork oak (Quercus suber L.) seedlings. One-year-old cork oak seedlings were grown in pots in a factorial experiment with four light treatments (68, 50, 15 and 5% of full sunlight) and two irrigation regimes: well watered (WW) and moderate drought stress (WS). Leaf predawn water potential, which was measured at the end of each of two cycles, did not differ among the light treatments. Water-use efficiency, assessed by carbon isotope composition (delta(13)C), tended to increase with increasing irradiance. The trend was similar in the WW and WS treatments, though with lower delta(13)C in all light treatments in the WW irrigation regime. Specific leaf area increased with decreasing irradiance, and was inversely correlated with delta(13)C. Thus, changes in delta(13)C could be explained in part by light-induced modifications in leaf morphology. The relationship between stomatal conductance to water vapor and net photosynthesis on a leaf area basis confirmed that seedlings in higher irradiances maintained a higher rate of carbon uptake at a particular stomatal conductance, implying that shaded seedlings have a lower water-use efficiency that is unrelated to water availability.

Interactive responses of Quercus suber L. seedlings to light and mild water stress: effects on morphology and gas exchange traits

“…These results from instantaneous measurements agree with carbon isotope discrimination measures made in this experiment and published previously (Aranda et al, 2007). Stomatal conductance variation across light environments was smaller than differences in photosynthesis leading to similar water expenses but lower carbon gain in shaded seedlings.…”

The relevance of seed size in modulating leaf physiology and early plant performance in two tree species

“…in carboxylation capacity and electron transport rate) enhancing leaf photosynthetic capacity. From our results, it seems that nitrogen tended to favour photosynthesis over stomatal conductance for Q. pyrenaica (Aranda et al 2007;Ponton et al 2002) and that it similarly stimulated photosynthesis and stomatal conductance for Q. petraea (Duan et al 2009;Meziane and Shipley 2001). Further examination of photosynthesis, stomatal conductance, and mesophyll conductance is needed to assess how consistent these differences are on the ecological requirements of the species and to what extent does 5 C inform on first-year WUE.…”

“…On the other hand, the microsite of seed dispersal affects leaf WUE in relation to the abundance of resources, such as water and light (Ehleringer and Cooper 1988). Under mild to moderate soil water deficit there is minor metabolic inhibition of net CO2 assimilation and stomatal regulation of water loss often leads to an increment of leaf WUE (Aranda et al 2007;Flexas and Medrano 2002). Light, on the other hand, favours WUE partly by increasing the number of mesophyll layers on the leaves, which in turn, increases the amount of nitrogen per unit area and their photosynthetic capacity relative to the diffusion rate of CO2 into the chloroplasts (Aranda et al 2007;Ponton et al 2002).…”

Phenotypic plasticity of Neonotonia wightii and Pueraria phaseoloidesgrown under different light intensities

“…A higher photosynthetic rate, as well as increased stomatal conductance, leaf blade thickness, stomata number per area, and cell wall thickness, were observed in young plant leaves of Cupania vernalis grown in full sunlight and 30% shade compared to those of plants grown in 50% and 70% shade (Lima Jr. et al 2006). In limited light conditions, photosynthetic and growth rates are lower, which negatively affects osmotic regulation and WUE (Aranda et al 2007). …”