Freezing and Ice Tolerance Tests for Winter Brassica
1992
Andrews, C.J. | Morrison, M.J.
Cold stress tolerances of winter brassicas (Brassica napus L., B. compestris L.) have frequently been reported from tests on leaves, without regard for the requirement of an intact crown meristem for overwinter survival. A method is described to determine the LD₅₀ of washed, trimmed plants for freezing and ice encasement. Plants were cold hardened in controlled environment or in the field and tested at the five-leaf stage. To determine freezing tolerance, units of five plants were sealed in polyethylene bags and survival determined of samples withdrawn during a 1 °C h⁻ˡ programmed temperature decline. For ice encasement tolerance, units of five plants were sealed in ice in polyethylene beakers and survival determined after thawing at intervals during exposure to -1 °C. The LD₅₀ was determined by interpolation or the Probit procedure. Significant separation of the cold stress tolerance of a number of cultivars of B. napus and B. campestris is presented. PRC Contribution no. 1400.
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