Náttúrufræðingurinn

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Náttúrufræðingurinn - 1983, Qupperneq 42

Náttúrufræðingurinn - 1983, Qupperneq 42
SUMMARY The effect of climate on grass growth and development by Aslaug Helgadóttir, The Agricultural Researclt Institute, Keldnaholti, 110 Reykjavík. Ecologically contrasting populations of Poa pratensis L. and Agrostis tenuis Sibth., collected from old fertilizer experiments in Sámsstadir and Akureyri, Iceland and Rothamsted, England, as well as from natural sites of high altitude in Iceland, were compared in spaced plant trials in Reading, England and at Korpa, Iceland. A number of morphological characters was recorded over a period of three years. In the present paper only three are reported; winter survival, heading date and reproductive ratios. Winter survival of all populations of both species was adequate at Reading. At Korpa, on the other hand, winter survival of British populations of A. tenuis was poor. Survival of British populations of P. pratensis was better, though not as good as that of Icelandic populations of both spe- cies. Differences between populations are related to their climatic origin, whereas differences between species are related to contrasting growth habits. Heading occurred earlier in P. pratensis than in A. tenuis at both Reading and Korpa. When grown at Reading, the natu- ral populations of P. pratensis from Gull- foss and Skálafell headed first, followed by the British populations, which were closely followed by the other Icelandic popula- tions. At Korpa, the natural populations headed slightly before the other Icelandic populations, but the British populations headed much later. In contrast to P. pratensis, all the Icelandic populations of A. tenuis headed much later than the Brit- ish populations at Reading and vivipary was observed in some of the Icelandic populations. At Korpa, heading occurred more or less simultaneously in the Ice- landic populations. These results indicate that the critical photoperiod for floral initiation is much longer in A. tenuis than in P. pratensis. The differences in floral development of the contrasting popula- tions are again related to their climatic origin. Populations of P. pratensis from Rothamsted had larger reproductive ratios at Reading than at Korpa, populations from Sámsstadir had larger ratios at Korpa, while populations from Akureyri, Gullfoss and Skálafell had similar ratios at both sites. The sporadic flowering in populations of A. tenuis from Sámsstadir and Akureyri resulted in fairly low repro- ductive ratios at Reading. The populations from Skálafel! and Gullfoss had, on the other hand, much higher ratios when grown at Reading than when grown at Korpa. The reproductive ratios of the con- trasting populations reflect the severity of their native habitat, but are though influ- enced by the ability of the two species to reproduce vegetatively. It is concluded that growth and develop- ment of the contrasting populations re- flects the seasonal pattern of climatic variation, particularly photoperiod and temperature, in their native habitat. 32
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