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 G eorgia (54 degrees 20'S) and the Rondane Mountains in Norway (61 degrees 42 'N) were studied in controlled environment in order to test the feasibility of transequatorial migration of this bipolar species. The South Georgia po pulation flowered more sparsely, but had much higher vegetative reproductio n capacity than the Rondane population. Both had an obligatory low temperat ure and/or short day (SD) requirement for inflorescence initiation. Althoug h heading and inflorescence development were enhanced by long days (LD) and higher temperature, neither population had any obligatory LD requirement f or flowering. No adaptation in the flowering requirements would thus have b een required for a step by step migration of this bipolar species on mounta in tops across the equator. Relative growth rate (RGR) and dry matter produ ction per plant were stimulated by LD in both populations, despite reductio n in photosynthetic capacity and chlorophyll content compared with SD condi tions. The main driving force for increased production in LD was LD-stimula tion of individual and total leaf area which more than compensated for redu ced 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 fo rmer. Chlorophyll a/b ratios were always higher in South Georgia than Ronda ne plants while they increased markedly with decreasing temperature, and we re always higher under SD than LD conditions in both population. Possible c onsequences for photosystem acclimation are discussed.