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Accueil du site → Doctorat → États-Unis → 1983 → Dormancy, germination, emergence and ecology of Gardner saltbush (Atriplex gardneri (Moq. ) D. Dietr. ) seeds

University of Wyoming (1983)

Dormancy, germination, emergence and ecology of Gardner saltbush (Atriplex gardneri (Moq. ) D. Dietr. ) seeds

Ansley, R.J. Jr.

Titre : Dormancy, germination, emergence and ecology of Gardner saltbush (Atriplex gardneri (Moq. ) D. Dietr. ) seeds

Auteur : Ansley, R.J. Jr.

Université de soutenance : University of Wyoming

Grade : Doctor of Philosophy (PhD) 1983

Résumé
Gardner saltbush (Atriplex gardneri (Moq.) D. Dietr.) provides valuable winter browse and is an important soil stabilizer in arid, alkaline, and saline areas of the intermountain region. However, seed dormancy and poor seedling vigor inhibit its potential for revegetation by direct seeding on disturbed lands. The objectives of this study were to (1) develop seed treatments which would overcome dormancy in Gardner saltbush seeds, (2) evaluate field establishment by direct seeding of Gardner saltbush, and (3) characterize seed dormancy, seedling vigor and some aspects of the ecology of germination in Gardner saltbush. Seeds collected from the Red Desert Basin of Wyoming were subjected to simulated environmental pretreatments dry after-ripening, scarification, washing, and cold stratification to overcome dormancy. Laboratory germination was evaluated. Subsequently, seedling vigor was observed by determining field emergence of similarly pretreated seeds at one irrigated and two dryland sites in Wyoming. Effects of 1 cm and 3 cm planting depth on emergence were also observed to further evaluate seedling vigor. In the laboratory, single and combined pretreatments removed dormancy to varying degrees. Dormancy was completely alleviated with 15 months dry after-ripening + scarification + 24 hours washing + 4 weeks stratification. Dry after-ripening and scarification appeared to facilitate effects of washing and stratification. Physiologically, indirect evidence was obtained suggesting both embryo and seedcoat mediated dormancy occur in Gardner saltbush. Ecologically, the various levels of germination response to simulated environmental pretreatments appeared to be an adaptation of Gardner saltbush seeds to ensure a temporal dispersal of release from dormancy. This increases the probability that under natural conditions some seedlings will emerge during times when the environment is amenable to seedling survival. Field emergence was far below laboratory germination for all treatments at all sites, indicating that establishment for this species is related to poor seedling vigor as much as to seed dormancy. The greatest emergence occurred from seeds pretreated with scarification + stratification, planted at 1 cm, and irrigated. Washing had little effect on enhancing field emergence. Washing, when combined with stratification, appeared to inhibit effects of stratification in scarified seed. Loss of this material, which could have been perisperm reserves, did not adversely affect blotter germination but may have been deleterious to proper seedling development.

Mots-clés : SEEDLINGS ; PLANT GROWTH ; SEEDS ; GERMINATION ; SHRUBS ; WYOMING ; FEDERAL REGION VIII ; GROWTH ; NORTH AMERICA ; PLANTS ; USA

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