Photoreceptive Pigments for Anthocyanin Synthesis in Apple Skin

Abstract

LIGHT is required for anthocyanin synthesis in many plant tissues. Appreciable synthesis of idaein (cyanidin 3-galactoside) in the apple skin, 1.0 × 10⁻⁹ moles/cm² of skin, requires 7 joules/cm² incident energy at the action maximum near 650 mμ and about three times as much energy in the region of the subsidiary maximum between 430 and 480 mμ (ref. 1). This high-energy photoreaction, which will later be referred to as the HER, usually must be followed by a photoreaction establishing the photomorphogenic pigment, phytochrome, in the far-red absorbing form (P_fr) which requires about 3 × 10⁻³ J/cm² for half saturation at the action maximum near 655 mμ (ref. 2). A number of photomorphogenic responses of plants including control of flowering and etiolation suppression, but not seed germination, involve both a high-energy reaction and the action of P_fr (ref. 3). The photoreceptive pigment has not previously been identified for the HER in apple skin or other objects and P_fr has not been shown to be necessary for idaein synthesis.