Effect of riboflavie and cyanide on blue light induction of betacyanin formation in Amamnthus caudatus seedlings

Abstract

The role of phyto chrome and flavins in blue light induction of betacyanin formation was studied in etiolated, three‐day‐old Amaranthus caudatus L. seedlings, using the criterion of far‐red reversibility and exogenously applied riboflavin and KCN. The effect of riboflavin was studied using high fluence rate blue light (42.7 :nmol m−2s−1nm−1 at 450 nm). When present in the incubation medium during illumination, riboflavin promoted the far‐red reversibility with short light treatments and suppressed the inductive action of continuous illumiaation. If added after light treatments, it promoted betacyanin formation. The filtration of blue light through the riboflavin solution caused profound changes in light quality without affecting the far‐red reversibility after 30 mm illumination. The effect of 1 mM KCN was tested with 70′% lower fluence of blue light. Cyanide caused the suppression of the inductive effect with 5 min blue light, which was accompanied by an enhancement of betacyanin induction by the terminal far‐red light pulse. With 30 min blue light, however, it caused the appearance of far‐red reversibility. The inductive effect of continuous blue illumination was slightly promoted by this Inhibitor. These results demonstrate that the effect of blue light on the pbyto chrome system is complex, whereas the physiological (inductive) action of the flavin triplet state is limited to low fluence, short blue light treatments.