The effect of liquid nitrogen on alfalfa seed viability, emergence, and broken cotyledons
1994
Wiesner, L.E. | Laufmann, J.E. | Stanwood, P.C. | Wheeler, L.J.
Exposure of alfalfa (Medicago sativa) seed to liquid nitrogen (LN2) was investigated to determine effects on germination, viability, broken cotyledons, emergence, and dry weight. Treatments evaluated were: LN2 liquid cooling (-196°C) with rapid (35°C) or normal (room temperature) warming, LN2 vapour phase cooling (-160°C) with normal warming, hand scarified LN2 vapour phase with normal warming, hand scarified, and non-scarified control. Prior to LN2 treatment, average percentage of hard seed of the four seed lots was 74% and average seed moisture content was 5.9%. Alfalfa accessions containing a high percentage of hard seed (up to 79%) had cotyledon breakage when exposed to LN2 vapour phase (-160°C) for 24 h. Cotyledon breakage was reduced when seed was scarified prior to LN2 exposure. Emergence was not significantly affected by any treatment except LN2 vapour phase with normal warming and the non-scarified control which had significantly less emergence due to hard seed content. Non-scarified control seedling weight was 80% heavier than LN2 liquid phase cooling with either rapid or normal warming. It is suggested that cotyledon breakage of alfalfa seed is associated with hard-seededness usually found in newly harvested seed and that cotyledon breakage reduces seedling growth.
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