An analysis of ecophysiological responses to drought in American Chestnut

Abstract

-With the anticipated reintroduction of blight resistant American chestnut (Castanea dentata [Marsh.] Borkh.), it is important to understand physiological responses of the species to various environmental stresses. To test the hypothesis that instantaneous water use efficiency (WUE i ) of American chestnut seedlings is increased by water stress, we measured gas exchange, leaf optical properties, and growth of American chestnut seedlings under well-watered and drought in both glasshouse and field conditions. Under well-watered conditions, field grown seedlings had consistently higher net photosynthesis (A net ) and leaf stomatal conductance (g s ) values than glasshouse seedlings. Under drought conditions, both field and glasshouse grown seedlings responded with a general increase in WUE i . Compared to well-watered conditions, drought stress significantly reduced the amount of light absorption regardless of growth environment. Under well-watered conditions, both field and glasshouse grown seedlings had similar maximum net photosynthesis rate (A max ) and maximum rate of ribulose 1,5 bisphosphate regeneration (J max ); however, maximum carboxylation (Vc max ), CO 2 compensation point (Γ), carboxylation efficiency (CE), and dark respiration (R) were substantially higher in the field grown seedlings. When WUE i values are compared to those of prevailing deciduous hardwood species that now inhabit American chestnuts once native range, we conclude that American chestnut has an advantageous preadaptation to water stress that might be a key survival determinant when it is reintroduced. leaf conductance / net photosynthesis / water-use efficiency Résumé -Analyse des réponses écophysiologiques à la sécheresse du châtaignier américain. Pour anticiper la réintroduction du châtaignier améri-cain (Castanea dentata [Marsh.] Borkh.) résistant à la rouille, il est important de comprendre les réponses physiologiques de cette espèce aux différents stress environnementaux. Pour tester l'hypothèse que l'efficience instantanée de l'eau (WUE i ) des semis de châtaignier américain est augmentée par le stress hydrique, nous avons mesuré les échanges gazeux, les propriétés optiques des feuilles et la croissance de semis bien alimentés en eau et de semis soumis à une sécheresse élevés en serre et en conditions extérieures. Dans le cas d'une bonne alimentation en eau, les semis poussant à l'extérieur ont eu constamment des valeurs plus élevées de photosynthèse nette (A net ) et de conductance foliaire (g s ) que celles des semis élevés en serre. Dans le cas de semis soumis à la sécheresse, les semis élevés en serre et ceux élevés en extérieur répondent par un accroissement général de WUE i . Comparativement aux conditions de bonne alimentation hydrique, la sécheresse réduit significativement la quantité de lumière absorbée indépendamment des conditions environnementales. En condition de bonne alimentation hydrique, les semis élevés en serre et en extérieur ont un taux maximum de photosynthèse nette (A max ) et un taux maximum de ...

Growth, physiology, and nutrient retranslocation in nitrogen-15 fertilized Quercus rubra seedlings

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PHOTOSYNTHETIC PERFORMANCE AND LEAF WATER POTENTIAL OF GULUPA (Passiflora edulis Sims, PASSIFLORACEAE) IN THE REPRODUCTIVE PHASE IN THREE LOCATIONS IN THE COLOMBIAN ANDES

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