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Accueil du site → Doctorat → États-Unis → 1996 → Effects of vesicular-arbuscular mycorrhizal (VAM) fungi on drought resistance of neem trees (Azadirachta indica A. Juss)

Texas A&M University (1996)

Effects of vesicular-arbuscular mycorrhizal (VAM) fungi on drought resistance of neem trees (Azadirachta indica A. Juss)

Phavaphutanon, Lop

Titre : Effects of vesicular-arbuscular mycorrhizal (VAM) fungi on drought resistance of neem trees (Azadirachta indica A. Juss)

Auteur : Phavaphutanon, Lop

Université de soutenance : Texas A&M University

Grade : Doctor of Philosophy (PhD) 1996

Résumé
Effects of vesicular arbuscular mycorrhizal (VAM) fungus Glomus intraradices Schenck and Smith, phosphorus (P), and drought on growth, nutrient uptake, gas exchange, water relations, water use efficiency, and carbon isotope discrimination $(\Delta)$ of neem trees were studied in a series of glasshouse experiments. VAM increased plant growth when soil P supply was low. Growth enhancement was associated with increased nutrient uptake, particularly P, increased photosynthetic rate (A), stomatal conductance $(g\sbs),$ and greater arbuscule and extraradical hyphae development. At high soil P, VAM colonization decreased and VAM and Non-VAM plants had comparable growth, tissue nutrition, A and $g\sbs.$ VAM and Non-VAM plants of comparable size and tissue nutrition responded to drought similarly. As a function of soil P supply, however, VAM compensated for low P supply, allowing VAM plants to have comparable growth, tissue P, and other physiological parameters as Non-VAM plants—which received higher P supply. Drought decreased growth, leaf area, transpiration (E), A, $g\sbs,$ leaf water potential, and turgor, but had less effect on relative water content and osmotic potential $(\Psi\sb\pi).$ Neem tree leaves had low $\Psi\sb\pi$ even under non-stressed conditions. Osmotic adjustment did not occur, but the relatively low $\Psi\sb\pi$ allowed turgor maintenance at peak stress. Plant water relations and A of stressed plants recovered to the level of non-stressed plants after rehydration, while $g\sbs$ and E partially recovered. Instantaneous water use efficiency (A/E) increased during drought and recovery, except for a decrease at peak stress due to very low A. The $\Delta$ of fully expanded mature leaves, remained constant regardless of VAM or drought treatments. However, $\Delta$ decreased in younger expanding leaves which developed during a drought period, indicating an increased long-term water use efficiency of these leaves. Water use efficiency estimated from the ratio of dry mass gained to water lost, in contrast, decreased during a drought period, due to less dry mass produced and loss of dry mass via leaf abscission. Growth of droughted plants resumed after rehydration. With low P supply, VAM increased growth and new root regeneration during a recovery period

Mots clés : Ecology, Glomus intraradices, Biological sciences, Botany

Accès au document : Proquest Dissertations & Theses

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