(2,4,6,7,9,12,18) and it has also been suggested that phytochrome may be the only photoreceptor involved, at least for HIR responses in the FR region (2,7,10,12,18). However, it has not been definitely proved that phytochrome is the only HIR photoreceptor and it has been suggested that other photoreactive systems may play a role in HIR responses (4,(13)(14)(15). There is some evidence for a contribution of photosynthesis to the synthesis of anthocyanins in green systems which have a functional photosynthetic apparatus, specifically apple skin sections and strawberry leaf disks (3, 4). Photosynthesis may play a role in the HIR anthocyanin synthesis of young, dark-grown seedlings exposed to continuous FR irradiation (13,14). However, the latter suggestion is not supported by results obtained in various laboratories, including our own (5,(10)(11)(12)19). The results submitted in this paper confirm and extend previous observations (11). One of the points in which we were specifically interested was to determine if the action of streptomycin on light-dependent anthocyanin synthesis would result in an alteration of the basic features of this response, that is, the R-FR reversibility and the relative effectiveness of different irradiance levels and of different spectral regions. Our interest is related to an assessment of the validity of the interpretation of in vivo inhibitor studies. Gilford 300-N spectrophotometer. The anthocyanin content of the extracts is presented as A530 -0.33 A657, a formula used to correct for the contribution of Chl and its degradation products in acid solution to the absorbance at 530 nm (11). The Chl content of the seedlings is presented as the A657 value of the acidic methanol extracts in Figure 2 and Table I. There is a good linear relationship between the absorbance of the acidic methanol extracts at 657 and the total Chl content of the seedlings as determined with extraction in 80% acetone and measurements according to Arnon (1); an A657 value of 0.5 corresponds to about 50 ,ug Chl/10 seedlings; the Arnon method was used to obtain the Chl data presented in Figures 1 and 3