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sur le développement des zones arides et semi-arides

Titre : Comparative response of Acacia holosericea and Acacia cowleana seedlings to water stress

Auteur : Gwaze, David Pasipanodya

Université de soutenance : Australian National University

Grade : Master of Science 1990

Résumé partiel
The responses to water stress of seedlings of Acacia holosericea A. Cunn. ex G. Don from both a high rainfall (HR) and low rainfall (LR) provenance, and of A. cowleana Tate. grown in small pots and in 1 metre long pots in a glasshouse were examined. In small pots, A. holosericea (HR) seedlings grew best in shoot height, diameter, leaf area and total biomass under well-watered and water stressed conditions. Although having lower concentrations of chlorophyll a and b in the phyllodes under well-watered conditions, A. holosericea (HR) seedlings had the highest stomatal conductances, assimilation and transpiration rates, and Ci/Ca ratio. Chlorophyll concentrations increased and chlorophyll a:b ratio decreased in all seedlings under water stress. Nitrogen concentrations in the phyllodes were similar in all seedlings and were unaffected by water stress whereas phosphorous concentrations, which were highest in A. holosericea (HR) and lowest in A. cowleana seedlings under well-watered conditions, were reduced by water stress to similar levels in all seedlings. Water stress reduced phyllode size and total phyllode area in seedlings of all provenances, and phyllode thickness increased in A. holosericea (HR), and decreased in A. cowleana seedlings. Specific leaf weights were increased by water stress only in A. cowleana seedlings. Water stress increased stomata ! density in A. holosericea (HR) and A. holosericea (LR) seedlings and decreased the number of phyllode hairs in all seedlings.

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