Effect of stage of seedling development upon the cold resistance of winter wheats
1934
Suneson, C.A. | Peltier, G.L.
Winter wheat seedlings in four 1-week interval stages of development from emergence to past tillering were compared for cold tolerance. Very young seedlings, presumably still dependent upon the endosperm to a considerable degree were found to excel all other more advanced stage of development groups in cold tolerance, whereas seedlings emerged from 7 to 12 days prior to controlled hardening and freezing, and probably on the verge of endosperm independence, were least cold tolerant. Hardening by exposure to a constant or an alternate (warm day and cold night) temperature near freezing revealed that actual cold resistance increased materially from exposure up to three weeks and none thereafter up to four weeks. The ranking of varieties was not affected by the duration of the hardening periods employed. Differences in varietal cold resistance relationships are indicated from (a) dissimilar growing temperatures or (b) dissimilar ages and stages of plant development at the time of initiating uniform hardening and freezing. These results, together with the seasonal effects reported in a previous paper (6), all point to the great importance of factors other than exposure to low temperatures and resultant high specific cold tolerance as determinators of the relative resistance of winter wheat varieties to cold.
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