Abstract

Seedlings often survive ice encasement stress better than mature plants under field conditions. However, in artificial ice encasement experiments with timothy, no significant difference in survival was detected between these two plant groups. At –2 °C seedlings accumulated respiration metabolites during ice encasement to higher levels than adult plants on dry weight or protein basis. No specific differences in metabolism between mature and young plants were detected although mature plants accumulated tartarate and acetate which were not detected in seedlings. Timothy plants accumulated ethanol, malate, lactate and CO2 and smaller amounts of propionate and pyruvate while citrate, fumarate and shikimate were at relatively low levels, and malonate was depleted. Therefore, higher survival of ice encased seedlings in field conditions cannot be ascribed to slower respiration rates or to different respiration pathways. Instead, the effect is probably brought about by more open, and thus less compacted soil, generated during seedbed preparation the previous year. This open soil structure imposes less severe oxygen shortage under ice.

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