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Developmental and physiological responses of winter wheat (Triticum aestivum L.) to selected environmental factors
Plant development is related to differentiation and initiation of organs while stomatal functioning is related to photosynthesis and transpiration. Temperature, photoperiod, and vernalization are major factors that control development in winter wheat. Leaf-to-air water vapor pressure deficit (VPD) is an important factor that affects stomatal functioning in wheat. In the first chapter of this dissertation, a generalized nonlinear vernalization response function [f(V)] was developed and evaluated. This function described the vernalization response of a wide range of wheat cultivars. In the second chapter, an existing wheat developmental model was modified by introducing the f(V) developed in the first chapter, dividing the vegetative phase (emergence-anthesis) into two sub-phases (emergence-terminal spikelet and terminal spikelet-anthesis), and modifying the temperature response function during the reproductive phase (anthesis-physiological maturity). The modified model improved the predictions of developmental stages of two winter wheat cultivars under field conditions compared to the original model. In the third chapter, a leaf appearance rate (LAR) chronology response function [f(C)] was developed and incorporated into an existing wheat LAR model. This function took into account seed reserves necessary for the rapid appearance of the first two leaves and the decreased appearance rate of later appearing leaves due to increasing distance leaves must traverse from the meristem to the whorl. Predictions of Haun stage of four winter wheat cultivars, grown under both growth chamber and field conditions, were improved by incorporating f(C) into the LAR model. In the fourth chapter, stomatal response to VPD in leaves at two different leaf positions on the stem during a natural soil drying cycle was studied. Stomatal response to VPD was different for the two leaves. This differential response may be an adaptation to the different environmental conditions during the development of each leaf, and anatomical and functional differences between leaves. The results indicate an improved approach to predict development and a better understanding of gas exchange response to VPD in winter wheat. ^
Streck, Nereu Augusto, "Developmental and physiological responses of winter wheat (Triticum aestivum L.) to selected environmental factors" (2002). ETD collection for University of Nebraska - Lincoln. AAI3055294.