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Environmental and Stress Physiology

Differences in Proteins Synthesized in Needles of Unshaded and Shaded Pinus ponderosa var Scopulorum Seedlings during Prolonged Drought ¹

U.S. Department of Agriculture Forest Service, Pacific Northwest Research Station, Forestry Sciences Laboratory, Corvallis, Oregon 97331, Department of Forest Science, Oregon State University, Corvallis, Oregon 97331

Proteins were radiolabeled and extracted from needles of Pinus ponderosa var scopulorum (Dougl. ex Laws.) seedlings progressively drought-stressed for about 1 month. A set of novel, low molecular weight proteins was detected in fluorographs of two-dimensional gels when relative water content of needles fell below 70%. Their synthesis was undetectable in the fully recovered seedlings within 48 hours after rewatering. In similarly stressed seedlings that were shaded to 10% full light, the low molecular weight polypeptides were not detected or appeared at very low levels. The shaded seedlings, in which drought tolerance was reduced, did not recover upon termination of the drought. The results suggest that protein synthesis induced by water deficit in drought-tolerant seedlings may contribute to resisting the effects of cellular dehydration.