Effects of blue and red light on photosynthetic 14CO2 uptake, and distribution of 14C in free and proteinbound amino acids in fern gametophytes [Dryopteris filix-mas (L) Schott

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Abstract
Morphogenesis and metabolism of the early gametophytes (= sporelings) of the common male fern are controlled by light. The “normal” two-dimensional development of the gametophytes in white or blue light is correlated with an increase in protein content; inred light alone, on the other hand, the sporelings remain filamentous, and the protein content is markedly lower (cf. Mohr, 1965). The problem has been whether blue light increases the rate of protein synthesis or decreases the rate of protein degradation. This problem was solved in the present paper by the use of 14CO2. Blue light promotes specifically the rate of protein synthesis as indicated by the increase of 14C incorporation into protein-bound amino acids under blue light as compared with red light. Using 14CO2 we have analyzed the kinetics of free amino acid synthesis (Fig. 4) and protein synthesis (Fig. 5) under steady state conditions of photosynthetic CO2 incorporation in blue or red light (Fig. 3). Under our conditions the rate of photosynthesis is about 1.5 times higher under blue light than under red light (Fig. 3, Table 1). The facts that the total pool sizes of the free amino acids are smaller in blue than in red light (v. Deimling and Mohr, 1967; Table 2) and that, on the other hand, the 14C-contents of the thoroughly labelled amino acid pools are virtually identical in blue and red (Table 3) indicate (a) that the pool sizes of these labelled amino acids may be equal in both light qualities and (b) that there is a compartmentation of free amino acid pools in the fern sporeling. This problem will be dealt with more in detail in a forthcoming paper on the behaviour of alanine in the fern sporeling (Payer, 1969). Protein synthesis is obviously much stronger under blue light than under red light. The detailed kinetics (Fig. 5b) indicate the involvement of two sorts of proteins: a relatively small part with high turnover which is rapidly labelled with a small but significant difference in red and blue, and a larger part with a slower turnover, the synthesis of which is strongly favored by blue light. — The first sort could be enzyme protein; the latter sort might be structural protein of the chloroplasts. These organelles increase dramaticly in size under the influence of blue light (Bergfeld, 1963). The amino acid composition of the protein, however, does not show any qualitative difference in gametophytes grown in blue or red light (v. Deimling and Mohr, 1967, Table 4).