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Polymorphism in macrocystis integrifolia bory in relation to water motion Pace, Danny Roy

Abstract

A field study in three parts was undertaken to investigate the relationships between the habit of Macrocystis integrifolia Bory and water movement. Morphological variation in time within populations was related to seasonal changes in wind direction and speed. Four sites covering a wide range of exposures, yet characterized by essentially the same water properties were sampled throughout a period of one year. In this way valid comparisons could also be made between populations. The sites were all situated in the vicinity [sic] of Barn-field on the west coast of Vancouver Island, B.C. A spot sampling study was undertaken to determine whether the trends established in the above study apply consistently throughout the range of exposures covered by Macrocystis in local waters. Samples were obtained from Ucluelet on Vancouver Island to Warren Island in southern Alaska. Through these studies several aspects of the habit were found to reflect the prevailing dynamic conditions to which the plant had been subjected throughout its development. A transplant study was carried out among the continuous sampling sites to establish the mechanism of response to dynamic conditions. Growth data obtained through the transplant study indicated that stipe elongation and blade initiation vary directly with water movement. Growth of individual blades appears to be independent of this factor. The results of the transplant study supported by variations observed within plants and within populations with time strongly suggest that the mechanism of response is phenotypic plasticity. However, plants observed on the outer coast were, in some respects, markedly distinct. Thus the possibility of a second mechanism operating under conditions of genetic isolation has not been discounted.

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