Water relations of cork oak (Quercus suber L.) seedlings in response to shading and moderate drought

Abstract

The interactive effects of light and drought on water relations and soluble sugars were addressed on Quercus suber L. seedlings grown under the combination of four irradiances and two soil water contents. Leaf water potentials at predawn and midday were lower for water stressed seedlings, independently of light environment. Osmotic potentials at full (Ψπ100) and zero turgor (Ψπ0) decreased with drought, under the four light treatments. However, the decline was greater with the development of water stress under the two treatments of higher light availability. The higher soluble sugar concentrations in seedlings grown under higher irradiances provoked a decrease of Ψπ0. The decrease in Ψπ100 and Ψπ0 in moderate stressed seedlings was accompanied by an increase in εmax. The lower ability for osmotic adjustment in seedlings grown under moderate water stress and low light environment suggested a lower efficiency in developing physiological mechanisms for drought tolerance in shade-grown seedlings. © INRA, EDP Sciences, 2005.