Interactive effects of drought and shade on three arid zone chenopod shrubs with contrasting distributions in relation to tree canopies

Abstract

Summary 1.Plants that grow beneath trees in arid systems may frequently experience both water and light limitation, although protection from high radiation loads during drought may compensate for a loss of productivity due to reduced light availability when water is plentiful. 2. We examined the effects of shading, during an imposed water deficit, on the carbon gain, stomatal conductance ( g s ) and shoot water potential ( Ψ s ) of seedlings of three shrubs: Atriplex vesicaria (Heward ex Benth.), a C 4 species, and Enchylaena tomentosa (R. Br.) and Rhagodia spinescens (R. Br.), which are restricted to shaded sites beneath trees. 3. Under conditions of limiting water, photosynthetic rates measured at saturating light ( A max ) were negative in high-light grown Enchylaena plants but remained positive in shade-grown plants. When water was not limiting, A max was reduced in shade-grown Atriplex but shade did not affect carbon gain in the other two species. 4. Atriplex Ψ s was higher in shaded than in unshaded plants, but in unshaded plants positive carbon gain was maintained at Ψ s below − 10 MPa. Stomatal conductance and A max decreased more slowly with increasing water deficit in shaded conditions in all species. 5. Atriplex was tolerant of a broader range of light and soil moisture conditions than Enchylaena , with Rhagodia intermediate between these two species. The interactive effect between drought and shade and the ecophysiological tolerances of these three species have consequences for their field distributions.

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

“…Thus, under growing light conditions, net photosynthesis rate was similar or even higher in this treatment than in the most illuminated one. This is in agreement with results from other studies on Quercus species which reported higher photosynthesis rate at intermediate light intensities (Castro-Díez et al, 2006;Prider and Facelli, 2004;Valladares et al, 2000).…”

“…The validity of the three above-mentioned hypotheses will depend on the species, the intensity of water stress, the range of light studied, the traits considered and many other experimental features as seedling age or environmental conditions. The tolerance of the different species to the combined effect of drought and shade determines their distribution and regeneration niches (Prider and Facelli, 2004;Sack, 2004). The question addressed in this study is how does the early development of cork oak growing under moderate water deficit change across a light gradient.…”

Patterns of tree seedling mortality in a temperate-mediterranean transition zone forest in Chile

“…The negative impact of drought on seedling growth and survival can be less in the shade than in high light (Sánchez-Gómez et al 2006). It has been suggested that, in dry environments, the negative impact of shade on light availability is more than compensated by the positive impact in reducing heat load and transpiration (Prider & Facelli 2004). The facilitative effects of shade have been documented as a crucial mechanism of regeneration in Mediterranean-type ecosystems (Maestre et al 2003).…”

Interactions between drought and shade on growth and physiological traits in two Populus cathayana populations

“…The knowledge of the impact of such interactions can help us to understand the adaptation of plants to different ecosystems and to develop the most appropriate forestation techniques to be used in fragile and extreme areas (Walters and Reich 1997). Therefore, investigations of the response of plants to combined drought and shade have gradually become a focus during recent years (Sack and Grubb 2002;Prider and Facelli 2004;Ashton et al 2006).…”