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Accueil du site → Doctorat → États-Unis → 1995 → Seedling vigor of wheat (Triticum turgidum L.) as affected by temperature and moisture during germination and emergence

Kansas State University (1995)

Seedling vigor of wheat (Triticum turgidum L.) as affected by temperature and moisture during germination and emergence

Fandi, Majid Najeib

Titre : Seedling vigor of wheat (Triticum turgidum L.) as affected by temperature and moisture during germination and emergence

Auteur : Fandi, Majid Najeib

Université de soutenance : Kansas State University

Grade : Doctor of Philosophy (PhD) 1995

Résumé
Wheat (Triticum turgidum L.) establishment is greatly influenced by environmental factors. Precipitation and temperature are the major factors that critically affect seed germination and seedling emergence in arid and semiarid areas. Wheat growers need to choose viable seed and the right planting date. Planting either too early or too late causes excessive growth or inadequate development. Early planting may also expose seeds to alternate wetting/drying periods because of periodic precipitation at the beginning of the growing season. Seed dehydration may improve seedling vigor but, if severe, may be fatal. Response farming system manipulates planting of crops in accordance with the prediction of environmental conditions of the growing season from climatic data. If an optimum planting date is determined according to the environmental factors through a response farming system concept, the risk of poor wheat establishment might be minimized. Soil moisture and temperature ranges that influence wheat establishment and response of two wheat cultivars to dehydration/hydration regimes during seed germination and seedling emergence were determined by experiments in the laboratory, growth chambers, and field. Amount of water imbibed by seed was dependent on both temperature and water potential. High and different amounts of water were imbibed by the cultivars during the first 2h. The total amount decreased with lowering temperature from 25 to 10$\sp\circ$C, which also slowed endosperm dry weight loss and the germination process but did not affect total germination. Time to germination was delayed as temperature and/or water potential were decreased. Dehydration of germinated seed shortened the time to emergence and decreased activity of $\alpha$-amylase at any temperature or water potential. Seed dehydration under field conditions may have an advantage to the establishment of wheat seedlings. Vigor index was determined more by temperature, which determines planting date, than by water potential. We conclude that planting date can be determined by thermal time, the accumulated heat that is needed for plant growth, rather than water time, the amount of water accumulated in the seed for germination and emergence

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