Effect of weather variants on field hardening of winter wheat
1938
Suneson, C.A. | Peltier, G.L.
The observed seasonal progression and annual variations in the cold resistance of field-grown winter wheats during a 6-year period at Lincoln, Nebr., together with associated variations in the environment, were utilized in a study of the more obvious weather factors contributing to field hardening. Two apparently distinct hardening stages were recognized in this work. During November and early December high daily temperature maxima in conjunction with high radiation appeared to be most conducive to hardening. High temperatures with low radiation or high radiation with low temperatures were least effective. High temperatures and radiation were effective only in increasing hardening under the influence of shortening days, however. Rather xeric conditions also appeared to favor hardening. This suggests that maximum hardening at this period results from a radiation-temperature balance reacting with day-length and drought influences to give maximum accumulation of organic reserves. Subsequent exposure to sustained low temperatures resulted in further progressive increases in hardiness for about 3 weeks. This low-temperature hardening reaction seemed always to effect maximum hardening for the season, the actual level apparently being determined by the efficiency and duration of the preceding growth-hardening stage. Controlled experiments showing a reduction in hardiness under the influence of reduced light intensity are reported.
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