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Accueil du site → Doctorat → États-Unis → 1965/1969 → GEOGRAPHIC VARIABILITY OF CREOSOTEBUSH (LARREA TRIDENTATA (D.C.) COV.) INRESPONSE TO MOISTURE AND TEMPERATURE STRESS

University of Arizona (1967)

GEOGRAPHIC VARIABILITY OF CREOSOTEBUSH (LARREA TRIDENTATA (D.C.) COV.) INRESPONSE TO MOISTURE AND TEMPERATURE STRESS

Saunier, Richard E.

Titre : GEOGRAPHIC VARIABILITY OF CREOSOTEBUSH (LARREA TRIDENTATA (D.C.) COV.) INRESPONSE TO MOISTURE AND TEMPERATURE STRESS

Auteur : Saunier, Richard E.

Université de soutenance : University of Arizona

Grade : Doctor of Philosophy (PhD) 1967

Résumé
One of the most widespread plant species in the arid southiwestern United States and northern Mexico is the creosotebush [Lavvsa tridentata (D.C.) Cov.]. To study its adaptation to the diverse environment found over its distribution, plants were collected from populations at Zapata, Texas (elevation 152 rn, annual precipitation  » 50.18 cm), Sheffield, Texas (elevation 609.6 m, annual precipitation 33.0 cm), and Bernardo, New Mexico (elevation 1,524 m, annual precipitation 20.32 cm). These plants were subjected to different conditions of soil moisture and air temperature in a plant growth environment chamber following a one-year equilibration period in the greenhouse. The following treatments were used : temperature (38 C daytime/15.5 C nighttime, 27 C daytime/4.5 C nighttime), moisture (daily waterings during the seven day treatment period, no water during the seven day treatment period), control (plants sampled four hours after watering and previous to treatment). Ecotypic variation appeared among the three populations in response to moisture stress. The bases of drought resistance were different. That for the Bernardo plants was one of drought tolerance, apparently an adaptation to the extreme dryness of the Bernardo area. It was shown as a loss of soluble sugars and an accumulation of proline and other glutamic acid family amino acids under moisture stress. The Sheffield and Zapata plants were more drought avoidant. Differences in the type of drought avoidance between plants from these two areas were evident. Zapata plants had a high initial moisture status which would carry them through the short dry conditions of the Zapata area. The Sheffield plants had a comparatively slower water loss rate which was thought to be an adaptation to the erratic precipitation of the Sheffield area. Clinal variation appeared in terms of susceptibility to lowered soil temperatures which affected the water absorption rate. The Bernardo plants were least susceptible, Sheffield plants were intermediate and the Zapata plants were most susceptible. These ecotypic and clinal differences may be contributing factors that enable the wide distribution of creosotebush over its varied environment

Mots clés : Creosote bush — Effect of stress on. ; Creosote bush — Geographical distribution. ; Plants — Effect of temperature on. ; Plants — Effect of soil moisture on.

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