Photocontrol of Anthocyanin Synthesis

Abstract

(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

Photocontrol of Anthocyanin Synthesis

“…In a previous note (10), we suggested that the reciprocity failure of the HIR could be explained in terms of phytochrome, and that the irradiance dependence perhaps was no more than (8,10), the fact that phytochrome was involved in the photocontrol of anthocyanin production under inductive conditions (8,9), and some ancillary observations (9,11,12) strongly suggested that the photoreceptor was phytochrome.…”

“…The light treatments were started 96 hr after sowing and were given in growth chambers equipped with the light sources described in previous papers (8)(9)(10)(11)(12). Temperature between the A657 values of the acidic methanol extracts and the Chl content of the seedlings (12). The volume of the extracts was either 15 ml (Figs.…”

“…Several factors are responsible for the difficulties encountered in identifying the HIR photoreceptors(s): (a) the variability of the spectral sensitivity of the HIR: some responses show maximum action in the FR region (1,2,7,8), some others in the BL (2,3,5,6), and some in the R (2); (b) the irradiance dependence of the HIR: it can be theoretically explained on the basis of phytochrome (1,7,14,17), but the assumptions made are not completely consistent with the variability of the spectral sensitivity of the HIR in different response-systemn combinations; (c) the reciprocity failure of the HIR under continuous irradiation: equal TRDs, obtained by reciprocal changes of irradiance and time (I x t = nI x tin), do not produce the same extent of the response (3, 13). The reciprocity failure suggests the possibility of a cooperation between different photoreceptors and creates difficulties in the interpretation of action spectroscopy studies (15).In a previous note (10), we suggested that the reciprocity failure of the HIR could be explained in terms of phytochrome, and that the irradiance dependence perhaps was no more than (8,10), the fact that phytochrome was involved in the photocontrol of anthocyanin production under inductive conditions (8, 9), and some ancillary observations (9, 11, 12) strongly suggested that the photoreceptor was phytochrome.Considerable amounts of anthocyanin are formed in cabbage seedlings exposed to continuous BL and R radiation (8,11,12). The objectives of the present study were to determine if reciprocity would be retained under intermittent BL and R irradiations, and if a comparative study of the action of continuous and cyclic light treatments could provide some information about the pigments active in the photocontrol of HIR anthocyanin synthesis under prolonged BL and R irradiations.…”

“…Considerable amounts of anthocyanin are formed in cabbage seedlings exposed to continuous BL and R radiation (8,11,12). The objectives of the present study were to determine if reciprocity would be retained under intermittent BL and R irradiations, and if a comparative study of the action of continuous and cyclic light treatments could provide some information about the pigments active in the photocontrol of HIR anthocyanin synthesis under prolonged BL and R irradiations.…”

“…11), incubation in streptomycin was used to enchance anthocyanin production (1 1, 12). The light treatments were started 96 hr after sowing and were given in growth chambers equipped with the light sources described in previous papers (8)(9)(10)(11)(12) …”