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

Abstract

-• The combined effect of water stress and light on seedlings of forest species is a key factor to determine the best silvicultural and afforestation practices in the Mediterranean area.• The aims of this work was (1) to determine the optimal light level for the early development of cork oak seedlings under mild water stress and (2) to test if the combined effect of water stress and light followed the trade-off, the facilitation or the orthogonal hypothesis.• Shade reduced instantaneous photosynthetic rates and water use efficiency in cork oak. However, seedlings grown under moderate shade (15% of full sunlight) were capable to accumulate similar amount of biomass than those grown under more illuminated environments by increasing their specific leaf area. Absolute differences in net photosynthesis between light treatments were higher in well watered than in water stressed seedlings. However, the impact of both factors on overall growth was orthogonal.• We concluded that cork oak development is impaired under deep shade (5% of full sunlight) but it can be optimal under moderate shade (15% of full sunlight) even under moderate water stress. Implications of these patterns on regeneration, cultivation and afforestation of cork oak are discussed. cork oak / photosynthesis rate / water use efficiency / shade acclimation / foliar anatomy Résumé -Réponses interactives de semis de Quercus suber L. à la lumière et à un stress hydrique modéré : effets sur la morphologie et sur les caractéristiques des échanges gazeux.• L'effet combiné du stress hydrique et de la lumière sur les semis est un facteur clé pour déterminer les meilleures pratiques pour la sylviculture et le reboisement dans la région méditerranéenne.• Le but de ce travail a été (1) de déterminer le niveau optimal de lumière pour le développement précoce des semis de chêne liège soumis à un stress hydrique modéré et (2) de tester si l'effet combiné du stress hydrique et de la lumière suit l'hypothèse de compensation, de facilitation ou d'orthogonalité.• L'ombre réduit le taux instantané de photosynthèse et l'efficience d'utilisation de l'eau chez le chêne liège. Cependant, les semis qui ont poussé sous une ombre modérée (15 % de la pleine lumière) ont été capables d'accumuler une biomasse totale similaire à celle des semis qui ont poussé sous de meilleures conditions d'éclairement en accroissant leur surface foliaire spécifique. Les différences absolues pour la photosynthèse nette, entre les traitements lumineux, ont été plus importantes pour les traitements bien alimentés en eau que pour les semis soumis à un stress hydrique. Cependant, l'impact des deux facteurs sur l'ensemble de la croissance a été orthogonal.• Nous en avons déduit que le développement du chêne liège est diminué sous une ombre profonde (5 % du plein éclairement) mais il peut être optimal sous une ombre modérée (15 % du plein éclairement) même en conditions de stress hydrique modéré. Les implications de ces modèles pour le chêne liège ont été discutées pour ce qui concerne la régénéra...

Intraspecific variation in drought response of Populus cathayana grown under ambient and enhanced UV-B radiation

“…Drought significantly decreased biomass accumulation in the two P. cathayana populations, similarly as previously reported for P. cathayana and other plants species (Anyia and Herzog, 2004;Li and Wang, 2003;Puértolas et al, 2008). Also for RWC, a significant decrease due to drought was observed.…”

“…However, UV-B radiation has been reported to alleviate drought stress of plants due to changes in epidermal anatomy (Petropoulou et al, 1995) and increases in carbon assimilation (Sullivan and Teramura, 1989). Meanwhile, interactive responses of Quercus suber L. seedlings to light and moderate water stress have been reported by Puértolas et al (2008). Studies on the combined effects of UV-B radiation and drought stress on trees have been conducted in some species, e.g., Mediterranean pines (Pinus pinea L.) (Petropoulou et al, 1995), olive (Olea europaea L.) (Noguės and Baker, 2000), Douglas fir (Pseudotsuga menziesii Franco) (Poulson et al, 2002) and willows (Salix myrsinifolia L.) (Turtola et al, 2006), and it appears that species differ in their responses to multiple stress factors.…”

Morphological response of Vitex negundo var. heterophylla and Ziziphus jujuba var. spinosa to the combined impact of drought and shade

“…Our results are consistent with some species studied by Sack (2004), such as Crataegus monogyna, Viburnum lantana and Viburnum opulus. The orthogonal result about the interaction of drought and shade has also been reported in some other species from both morphological and physiological aspects (Sack and Grubb 2002;Sack 2004;Feng and Li 2007;Puértolas et al 2008). …”

Drought susceptibility and recovery of transplanted Quercus rubra seedlings in relation to root system morphology

“…4A). This response may correspond to that of cork oak (Quercus suber L.) seedlings, in which increased specific leaf area associated with shading under water limiting conditions resulted in equivalent biomass production despite reductions in instantaneous photosynthetic rates (Puértolas et al, 2008). In addition, N and carbohydrate reserves are essential for new growth development before significant root uptake and photosynthesis (Salifu et al, 2008;Sloan and Jacobs, 2008).…”