Response of protein and carbohydrate metabolism of Scots pine seedlings to low temperature

The short-term response of protein and carbohydrate metabolism of Scots pine (Pinus sylvestris L.) seedlings to low temperature was studied previous to the onset of growth. Two-year-old potted seedlings grown outdoors were placed in growth chambers for an adaptation period of 2 days at 18 °C in a long photoperiod. The cold treatment (4 °C) was then performed on half of the plants. One-year-old needles were harvested for analyses before (day 0), as well as 1, 4, 7, 10 and 14 days after the beginning of the experiment. The effects of cold treatment were rapidly seen as an inhibition of growth, a decrease in the water and osmotic potentials, and a change in carbohydrate metabolism. The concentration of soluble sugars in needles initially increased in seedlings placed at 4 °C, but decreased again during the last 7 days. The starch content of cold-treated needles decreased during the first 7 days, but increased during the second week of the experiment. Exposure of seedlings to 18 °C caused a decrease in the starch concentration of needles after day 4, but no effects were detected in sugar concentration. No change in specific proteins or in their quantity, as determined by SDS-PAGE, due to low temperature was observed. Immunoblots using a dehydrin antibody detected a 50-kDa protein in all samples, as well as a 42-kDa-dehydrin that was missing from the day 1 and 14 samples. The results of this study indicate that protein and carbohydrate metabolism of Scots pine adjust to low temperature within less than ten days. Neither soluble protein patterns nor dehydrin-proteins of needles are markedly altered by cold treatment.