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The paper describes how absolute values of pollen deposition may be calculated from the results of volumetric sampling, supplemented by routine meteorological data. Daily mean values of concentration of birch pollen in the air at Lerwick, Shetland in 1970 and 1971 are presented, and these are used to calculate daily and annual depositions. The results are consistent with what is known about the occurrence of tree pollen in fossil and recent deposits in Shetland. [ABSTRACT FROM AUTHOR]

The aim of the investigation was to find a method of growing birch seedlings with a constant optimum nutrient status. The studies in this paper have indicated important factors in such a growth method which must be comprised in a definition of nutrient requirements. The optimum nutrient proportions in the seedlings and the optimum total concentration in the solution must be known. Special attention must be paid to the ratio between NH4+ and NO3- in the solution and in the uptake. The amounts of nutrients taken up at optimum nutrition can be followed by measurement of pH and conductivity. Thus, the nutrients consumed may be replaced by titrations which may be automated by standard equipment. The nutrient proportions to be added are determined by the optimum internal proportions. It is not necessary to change the nutrient solution even if the volume is relatively small in relation to plant mass. There was no evidence of effects of accumulation of root exudates or infections. By using the system described, it is possible to attain considerably greater fresh and dry matter production in birch seedlings than when an optimum conventional solution is used. [ABSTRACT FROM AUTHOR]

Experiments were carried out with three seed lots of Betula nana collected in 1967 from different localities in Norway. Seeds were stratified for 0-20 days in dark at +2-+3°C on filter papers moistened with distilled water, or treated with solution of GA3 for 24 h at room temperature, and then moved into special germination boxes that were placed in different temperature conditions. All the seed lots had conditional dormancy. Quantitatively, the dormancy was different in the different in the different seed lots (provenances), but there were no qualitative difference in the reaction to stratification, gibberellic acid and to germination temperature. Differences between seed lots may have been due to different stage of seed development. The dormancy was deepest at low temperatures (12 and 15°C) decreasing gradually with increasing temperature (to 24°C). The dormancy was effectively broken by a short stratification (from 5 to 15 days), and by treatment with gibberellic acid. The deeper the dormancy and the lower the germination temperature the longer the stratification that was needed for maximum germination. Similarly, the concentration of GA3 needed for maximum germination increased with decreasing temperature and with increasing dormancy. [ABSTRACT FROM AUTHOR]