RESPONSES O F REPRODUCTIVE TRAITS TO SHORT-TERM ARTIFICIAL WARMING IN A DECIDUOUS ALPINE SHRUB GEUM PENTAPETAL UM (ROSACEAE)

Abstract: We examined the effects of short term artificial warming from 4 July to 19 September 1996 (78 days) in an open top chamber (OTC) on fruit production of a deciduous alpine shrub Geum pentapetalum (L.) Makino (Rosaceae) in the Tateyama Range, Toyama, Japan. Daily maximum temperature in the growing period significantly increased ca. 3. 6 T inside the OTC as compared to outside the chamber, while daily minimum temperature significantly decreased ca. 1. 3 T inside the OTC. Daily mean temperature was not significantly different inside and outside the OTC. There were not any significant differences of shoot characteristics such as the number of leaves, total leaf mass and current stem weight inside and outside the OTC. Dry weight of the main body of the achene (including seed) and individual achene size (IAS) were significantly increased by OTC treatment, while the plume was not. Seed ripening, estimated number of achenes (ENA) and estimated total achene mass per shoot (EAM) slightly increased inside the OTC, but they were not significantly different between the shoots affected by OTC and the unaffected. EAM was sig-nificantly positively correlated with current basal stem weight both in OTC-affected and-unaffected shoots. Analysis of covariance showed that EAM in a given stem size was significantly higher in OTC affected shoots than in the-unaffected shoots. These results imply an importance of interaction between fruit production and shoot size when we assess the effects of artificial warming on reproductive traits. Thus, we found that short-term artificial warming first affected the size rather than the number of seeds and fruits, and the reproductive organs were more sensitive to warming than vegetative organs of Geum pentapetalum, at least according to the dry weight based analysis. key words: alpine plant, artificial warming, Geum pentapetalum, plant size, seed productio