Chemical Composition of Mountain Birch (Betula Pubescens Ehrh.), and Lowland Birch (Betula Pendula Roth.) Seedlings, Grown at Varying Temperature, Light and Photoperiod

1991

27 S.

zahlr. Lit. Ang.

Unselbständiges Werk

200037928

Seedling of four populations of mountain birch (Betula pubescens Erh.) and one population of lowland birch (Betula pendula Roth.), grown for 6 weeks at different temperatures (9 Grad, 15 Grad and 21 Grad C), light intensities and photoperiods, were analyzed for chemical composition of leaf, stem and root tissue. There was a strong accumulation of non-structural carbohydrates in the stem and root tissue, particularly at low temperature and short daylengths as a result of slow growth. A similar but weaker accumulation was found in total nitrogen content. The main sink for nitrogen was found to be the leaves, where the strongest accumulation was found at 21 Grad C. There was no corresponding temperature effect on leaf carbohydrates. As a result the source strength, measured by the C/N ratio between total non-structural carbohydrates and total nitrogen, decreased with increasing temperature. The highest source strength, when averaging over daylengths, was found in the slow-growing arctic mountain birch popuation from Kevo, North Finland. A similar but weaker accumulation than for nitrogen was also found in the total phosphorus content while the chlorophyll content in leaves showed a strong increase with temperature. A certain effect due to growth cessation was found in the total nitrogen and phosphorous content as well as in the chlorophyll content in the leaves, especially in th northern Kevo population, at short days and low temperatures. At the same time there was a strong increase in water soluble proteins and soluble sugars in leaves, probably as a result of hardening, most obvious in the northern population.