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Accueil du site → Doctorat → États-Unis → 1992 → Water uptake and storage in diverse arid-land plants

University of California, Los Angeles (1992)

Water uptake and storage in diverse arid-land plants

North, Gretchen Barrow

Titre : Water uptake and storage in diverse arid-land plants

Auteur : North, Gretchen Barrow.

Université de soutenance : University of California, Los Angeles

Grade : Doctor of Philosophy (Ph. D.) 1992.

Résumé
Changes in hydraulic conductivity (Lp) and anatomy were investigated for roots of Agave deserti after drying and rewetting. At 30 d of drought, Lp had declined less than twofold for older nodal roots, tenfold for young nodal roots, and more than 20-fold for lateral roots. These decreases coincided with increases in cortical lacunae caused by cell shrinkage and collapse, and reduction of lacunae in response to rewetting after 7 d of drought corresponded to levels of recovery in Lp. Increases in suberization in response to drying coincided with decreases in Lp. Air embolism reduced axial conductance (K$\sb\rm h$) by 98% for lateral roots, 35% for young nodal roots, and 20% for older nodal roots at 7 d of drought. Drought-induced changes in Lp and anatomy were investigated for roots of Ferocactus acanthodes and Opuntia ficus-indica. Drying for 30 d caused little change in Lp or structure for 1-mo-old roots, primarily due to the formation of soil sheaths in the root hair zone. For 3-mo-old roots, Lp declined three- to fivefold, partly because of cortical lacunae. For 12-mo-old roots, the dehydration of suberized peridermal layers led to a two- to threefold decline in Lp. Air embolism caused by 30 d of drying decreased K$\sb\rm h$ by 53%, 97%, and 98% for 1-, 3-, and 12-mo-old roots, respectively. Rewetting restored K$\sb\rm h$ to initial values within 7 d for all root ages. Lp after rewetting attained 100% of its initial value for 1-mo-old roots and about 60% for 3- and 12-mo-old roots. The role of capacitance in supplying water to the transpiration stream was investigated for Cucurbita foetidissima, C. palmata, and Marah macrocarpus. For M. macrocarpus, total leaf capacitance could sustain maximal daily transpiration for 11 min, and for the two Cucurbita species, only 1 min. Root tuber capacitance could sustain maximal transpiration of 2 h for M. macrocarpus, yet for only 5 min for the two Cucurbita species. Tuber storage resistance was high for the three species and xylem resistance was low, implying that transpired water was more likely to come from the soil than from storage.

Mots clés : Plants — Absorption of water. ; Plant-water relationships. ; Arid regions ecology.

Annonce (WorldCat)

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Page publiée le 7 novembre 2013, mise à jour le 29 juin 2018