FIG. 17. Relative changes in weight of individual plant organs and of the total plant weight under the influence of different ligth conditions (Mean values of Pinus silvestris, Pseudotsuga taxifolia, Betula pendula, Robinia pseudoacacia, Alnus glutinosa, and Quercus borealis) I = 85 - 100%, II = 55 - 70%, III = 30 - 45% and IV = 15% of full daylight (after Lyr et al., 1963).

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