Informations et ressources scientifiques
sur le développement des zones arides et semi-arides

Accueil du site → Doctorat → États-Unis → 1989 → Stomatal and nonstomatal limitations to photosynthesis in Phaseolus vulgaris L. and Phaseolus acutifolius Gray in response to water stress

University of Minnesota (1989)

Stomatal and nonstomatal limitations to photosynthesis in Phaseolus vulgaris L. and Phaseolus acutifolius Gray in response to water stress

Castonguay, Yves

Titre : Stomatal and nonstomatal limitations to photosynthesis in Phaseolus vulgaris L. and Phaseolus acutifolius Gray in response to water stress

Auteur : Castonguay, Yves

Université de soutenance : University of Minnesota

Grade : Doctor of Philosophy (PhD) 1989

Résumé
Phaseolus acutifolius Gray (Pa) is well adapted to arid conditions and might be a valuable source of genes to improve the drought tolerance of P. vulgaris L. (Pv). The objective of this research was to characterize stomatal and nonstomatal limitations to photosynthesis and identify genotypic differences that could be exploited in a plant improvement program. Light and CO$\sb2$ saturated rates of photosynthetic O$\sb2$ evolution and chlorophyll fluorescence were used to measure the mesophyll tolerance to dehydration. Leaf abrasion was necessary to insure that photosynthetic rates were CO$\sb2$ saturated. When CO$\sb2$ saturated, the photosynthetic rates were equally sensitive to dehydration in the two species. Photosynthesis decrease with tissue dehydration was not related to damage to the photosynthetic light reactions. Plants were exposed to three levels of water stress by surrounding the soil with a semipermeable membrane and adjusting the osmotic potential of the external nutrient solution with PEG. Total dry matter decreased similarly in the two species in response to water stress. Moderate stress increased the root/shoot ratio in Pa but not in Pv. Pressure-volume curve analyses indicated that both species osmotically adjusted to the same extent in response to water stress. Abaxial leaf diffusion resistance increased more rapidly in Pa than in Pv with increased water deficit. Gas exchange analysis showed higher net photosynthetic rates (Pn) in Pa than in Pv at high to moderately low leaf water potentials. Pn declined more in Pa than in Pv with increased water deficit. This response was related to a greater stomatal closure at lower leaf water potential. A higher Pn rate at all internal CO$\sb2$ concentration (Ci) in Pa resulted in a higher water use efficiency than in Pv. Cuticular conductance to water vapor was smaller in Pa than in Pv and consequently dark transpiration occurred at a lower rate in Pa. Stomatal response to increased leaf-air vapor pressure difference was similar in the two species. These results suggest that Pa adaptation to arid environments relies primarily on dehydration postponement mechanisms.

Mots clés : Biological sciences, Botany, Phaseolus acutifolius

Accès au document : Proquest Dissertations & Theses

Page publiée le 12 avril 2015, mise à jour le 29 décembre 2016