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Phenology and gas exchange in winter wheat (Triticum aestivum L.)
Crop phenology refers to development, differentiation, and initiation of organs. Accurate prediction of phenology is important for management practice as well as for improving crop simulation models. Gas exchange is a process that is directly related to dry matter accumulation and grain yield. In the first part of this study, a three-year field experiment was conducted to develop an algorithm to predict leaf appearance and phenological stages in winter wheat. The resulting nonlinear model was validated using independent field data. In the nonlinear model, the daily leaf appearance rate (DLAR) was simulated based on the product of maximum DLAR, a temperature function [f(T)] and a photoperiod function [f(P)]. The f(T) was a function of cardinal temperatures for leaf appearance, while the f(P) was an exponential function. The nonlinear model accurately predicted leaf appearance rate, and the root mean square error (RMSE) was less than 1 leaf for predicting main stem Haun stage. For predicting the phenological stages, the daily development rate was simulated in a similar way to the leaf appearance, based on the product of a maximum development rate (Rmax), a f(T), a f(P), and a vernalization function. The nonlinear model performed very well for predicting phenological stages. In the second part of this study, a two-year field experiment was conducted to investigate influences of plant available soil water (PASW) on the responses of gas exchange parameters to vapor pressure deficit (VPD) and photosynthetic photon flux density (PPFD), and on the differences in gas exchange parameters, water use efficiency (WUE), and carbon isotope discrimination (Δ) between new and old cultivars. Plant available soil water had a significant effect on the responses of gas exchange parameters to increased VPD and PPFD. The PASW also affect the genotypic variation in gas exchange parameters. The older cultivars had greater net CO2 assimilation rate, stomatal conductance, transpiration rate and WUE than the newer cultivars under water stress. Significant differences in Δ values among cultivars were observed; the oldest cultivar had the lowest Δ values. The cultivars with lower Δ value had higher WUE underwater stress. The results of this study are helpful for improving prediction of wheat phenology, and for better understanding plant adaptation to differing environmental conditions. ^
Agriculture, Agronomy|Biology, Plant Physiology
Xue, Qingwu, "Phenology and gas exchange in winter wheat (Triticum aestivum L.)" (2000). ETD collection for University of Nebraska - Lincoln. AAI9967411.