Growth and Reproduction Capacities of Two Bipolar Phleum alpinum Populations from Norway and South Georgia

Growth and development of two populations of Phleum alpinum L. from South Georgia (54?20'S) and the Rondane Mountains in Norway (61?42'N) were studied in controlled environment in order to test the feasibility of transequatorial migration of this bipolar species. The South Georgia population flowered more sparsely, but had much higher vegetative reproduction capacity than the Rondane population. Both had an obligatory low temperature and/or short day (SD) requirement for inflorescence initiation. Although heading and inflorescence development were enhanced by long days (LD) and higher temperature, neither population had any obligatory LD requirement for flowering. No adaptation in the flowering requirements would thus have been required for a step by step migration of this bipolar species on mountain tops across the equator. Relative growth rate (RGR) and dry matter production per plant were stimulated by LD in both populations, despite reduction in photosynthetic capacity and chlorophyll content compared with SD conditions. The main driving force for increased production in LD was LD-stimulation of individual and total leaf area which more than compensated for reduced photosynthesis per unit leaf area. Relative growth rate, photosynthetic capacity, and chlorophyll content were less in South Georgia than Rondane plants, while specific leaf area and shoot/root ratio were higher in the former. Chlorophyll alb ratios were always higher in South Georgia than Rondane plants while they increased markedly with decreasing temperature, and were always higher under SD than LD conditions in both population. Possible consequences for photosystem acclimation are discussed.