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

Abstract

Abstract:The morphological and physiological responses of two contrasting Populus cathayana Rehd. populations to three light regimes, full sunlight (control), 33% full sunlight (moderate shade), and 12% full sunlight (severe shade), were investigated under well-watered and drought conditions. The populations were from Hanyuan (relatively more annual rainfall and less annual solar radiation) and Ledu (less annual rainfall and more annual solar radiation) in western China. In both populations, drought-treated plants exhibited reduced growth, leaf relative water content, net photosynthesis, and maximal efficiency of photosystem II (PSII); increased levels of chlorophyll, carotenoid, abscisic acid, and carbon isotope composition; and a greater accumulation of malondialdehyde (MDA) than did well-watered plants. There was an apparent alleviation of drought effects by moderate shade, especially in the Hanyuan population, as indicated by the higher leaf relative water content, net photosynthesis, stomatal conductance, and maximal efficiency of PSII and the lower MDA content. On the other hand, an apparent aggravation of drought effects by severe shade was also observed, especially in the Ledu population, as indicated by the lower total biomass and net photosynthesis and the higher MDA content. Moreover, the Hanyuan population was more shade tolerant and drought sensitive than the Ledu population. dans l'ouest de la Chine. Dans les deux populations, la croissance, la teneur relative en eau dans les feuilles, la photosynthèse nette et l'efficacité maximale de PSII étaient plus faibles et les quantités de chlorophylle, de carotène, d'acide abscissique, la composition isotopique du carbone ainsi que l'accumulation de propanedial étaient plus élevées chez les plants exposés à la sécheresse que chez les plants bien arrosés. Les effets de la sécheresse ont apparemment été atténués par un ombrage modéré, spécialement dans la population de Hanyuan, tel que l'indiquaient une teneur relative en eau dans les feuilles, une photosynthèse nette, une conductance stomatale et une efficacité maximale de photosystème II (PSII) plus élevées ainsi qu'un contenu en propanedial plus faible. D'un autre côté, les effets de la sécheresse ont apparemment été aggravés par des conditions très ombragées, spécialement dans la population de Ledu, tel que l'indiquaient la biomasse totale et la photosynthèse nette plus faibles ainsi que le contenu en propanedial plus élevé. De plus, la population de Hanyuan était plus tolérante à l'ombre et plus sensible à la sécheresse que la population de Ledu.[Traduit par la Rédaction]

Effect of drought and ABA on growth, photosynthesis and antioxidant system of Cotinus coggygria seedlings under two different light conditions

“…Drought-induced increases in chlorophyll contents were detected here and also in previous studies (Huang et al, 2008). In addition, we found that exogenous ABA application did not affect the chlorophyll content, but there were differences in chla/b in response to drought at both light levels.…”

“…Furthermore, ␦ 13 C induced by drought, exogenous ABA application and the D + ABA treatment under SL was lower than that under FL, which suggests that the water use efficiency of seedlings is more sensitive to drought, ABA application and the combination of drought and ABA under FL. It may be that shade aids plants to maintain a higher tissue water content that mitigates drought stress (Huang et al, 2008). In addition, plant hormones play critical roles in regulating plant responses to stressful environments .…”

“…In the drought treatment, the pots were watered to 30% FC every second day to keep drought levels in the soil. Evaporation from the soil surface was prevented by enclosing all pots in plastic bags sealed at the base of the stem of each seedling as described by Huang et al (2008). In the exogenous ABA treatment, all pots were given exogenous ABA (+ABA) ((±)-cis, trans-abscisic acid, Sigma, St. Louis, MO, USA) by spraying the leaves with 10 ml of 50 M (±) ABA per day and seedling.…”

“…Light and water availability are main environmental factors affecting plant survival and growth, and determining the distribution of plants at global scales (Ashton et al, 2006;Quero et al, 2006). In some previous studies, biochemical, physiological and structural responses of seedlings to the combination of drought and shade have been reported, and the results have showed both negatively and positively correlated but also independent interaction effects between shade and drought (Aranda et al, 2005;Huang et al, 2008;Duan et al, 2009). However, the underlying mechanisms are poorly known.…”

“…ABA can increase the activity of the reactive oxygen species (ROS) scavenging enzymes, superoxide dismutase (SOD) and catalase (CAT), and reduce malondialdehyde (MDA) formation (Lei et al, 2006;Duan et al, 2007). On the other hand, shade treatment can affect the endogenous hormone levels (Huang et al, 2008). However, the combined effect of drought, exogenous ABA and shade treatment on plant growth and physiological traits has not been previously reported.…”