Variations physiologiques dans des populations de thuyas géants (Thuja plicata Donn ex D. Don) en réponse à une sécheresse courte

Abstract

Abstract• Variation in the ability of western redcedar (Thuja plicata Donn ex D. Don) populations to withstand water stress may exist because this species is found in coastal and interior biogeoclimatic subzones representing the full range of precipitation regimes in British Columbia, Canada.• Seven western redcedar populations from locations in British Columbia, representing a wide range of habitat types, were assessed for their gas exchange and water relations response to controlled drought.• Before drought, population variation occurred in stomatal conductance, net CO 2 assimilation rate and intrinsic water use efficiency and the relative water content at turgor loss point. During drought, populations had different responses of net CO 2 assimilation to decreasing predawn shoot water potential. After drought, populations differed in stomatal conductance and intrinsic water use efficiency, plus osmotic potential at turgor loss point, osmotic potential at saturation and apparent cuticular transpiration. Western redcedar populations from drier-inland habitats had a lower osmotic potential at turgor loss point, lower relative water content at turgor loss point and lower apparent cuticular transpiration in response to drought than populations from coastal origin with temperate maritime habitat.• Reduction of cuticular water loss and adjustments of cellular water relations in response to drought was found to occur among seven western redcedar populations originating along a precipitation gradient while; there were minimal population differences in the gas exchange response to drought.Mots-clés : performances de populations de thuyas géants / échanges gazeux / relations hydriques / réponse à la sécheresse Résumé -Variations physiologiques dans des populations de thuyas géants (Thuja plicata Donn ex D. Don) en réponse à une sécheresse courte.• Les variations de capacité à résister au déficit hydrique dans des populations de thuyas géants (Thuja plicata Donn Ex D. Don) apparaissent parce que cette espèce se rencontre dans les sous-zones biogéoclimatiques côtières et de l'intérieur représentant l'éventail complet de régimes de précipitations en Colombie britannique (Canada).• Sept populations de thuyas géants issues de sites de Colombie britannique, représentant un large éventail des types d'habitats, ont été évaluées pour leurs échanges gazeux et leurs relations hydriques en réponse à une sécheresse contrôlée.• Avant la sécheresse, une variabilité existait entre populations pour la conductance stomatique, l'assimilation nette de CO 2 , l'efficience intrinsèque d'utilisation de l'eau et la teneur relative en eau au point de perte de turgescence. Pendant la sécheresse, les populations ont présenté des réponses diffé-rentes de l'assimilation nette de CO 2 à la baisse du potentiel hydrique de base. Après la sécheresse, les populations différaient en conductance stomatique et efficience intrinsèque d'utilisation de l'eau, mais également en potentiel osmotique au point de perte de turgescence, en potentiel osmotique à satura...

The effect of vapour pressure deficit on stomatal conductance, sap pH and leaf-specific hydraulic conductance inEucalyptus globulusclones grown under two watering regimes

“…Stomatal conductance has long been considered of key interest in the study of plant adaptation to drought and high temperatures (Pearce et al, 2005;Grossnickle and Russell, 2010). This is particularly true for E. globulus plantations established under Mediterranean climates, because (1) high vapour pressure deficits (VPDs) may result in water stress even when soil water is abundant, and (2) E. globulus was found to reach its highest productivities through lower water-use efficiency in field trials established in south-western Spain (Pita et al, 2001).…”

Canary in the forest?—Tree mortality and canopy dieback of western redcedar linked to drier and warmer summers

“…Compared to coastal populations, radial growth rates of WRC trees in interior populations were more resistant and resilient to drought (Figure 4; Table 2), though drought severity was slightly lower at sites in interior populations in 2015 (Figure S9). The higher growth resistance of WRC trees in interior relative to coastal populations is consistent with their greater water use efficiency and drought tolerance, specifically osmotic potential and relative water content at turgor loss point (Grossnickle & Russell, 2010). North to south within WRC populations, genetic variation is minimal (Shalev et al, 2022).…”

“…North to south within WRC populations, genetic variation is minimal (Shalev et al, 2022). However, differences between populations in their physiological and growth response to drought may indicate that interior populations are better adapted to continued warming and drying summer conditions and may be a potential source for seeds for assisted migration of coastal populations (Grossnickle & Russell, 2010). Acclimation in growth and physiological responses to hotter and drier environmental conditions through adjustment in foliar anatomy has also been demonstrated within a WRC population (Tomaszewski, 2022), but the capacity of acclimation and/or adaptation to enable survival of WRC under expected future climate change remains an unresolved question.…”

Canary in the Forest? – Tree mortality and canopy dieback of western redcedar linked to drier and warmer summer conditions

“…S9). The higher growth resistance of WRC trees in interior relative to coastal populations is consistent with their greater water use efficiency and drought tolerance, specifically osmotic potential and relative water content at turgor loss point (Grossnickle and Russell 2010). Though there is minimal genetic variation north to south within WRC populations (Shalev et al 2022, Rehfeldt 1994), differences between populations in physiological and growth response to drought in the southern half (climatically warmer and drier) of its range may indicate that interior populations are better adapted to continued warming and drying summer conditions.…”