Flavonoid Complexes in Pisum sativum. II. Effects of Red and Far-Red Light on Biosynthesis of Kaempferol Complexes and on Growth in Etiolated Plumules

Abstract

Flavonoicl synthesis is, in many plants, either pro-mloted by light or (lepen(lent upoIn light (3). The nature of this light re(quirement appears to vary depending UpOnl the conmpounds ancl plant miiaterials being studiedl (15, 17, 19, 21, 23), and little is known regalrding the relationship between photoinduced synthesis of these compounds and photoincluced growth an(l (levelopmlenit. In etiolated pea plumules, low intensity red light stimulates both leaf growth (20, 25) ancl the procluction of an in(lole-3-acetic atcid oxidcase inhibitor (13). This inhibitor has quite recently been found to contain kaeempferol-3-triglu-coside (KG) and kaemplpferol-3-(triglucosv-l-p-couma-rate) (KGC) (9,10,18). The purposes of the present investigation were, firstly, to (letermine the effect of re(d an(d far-re(d irradiation on the biosynthesis of KGC an(d KG, and, seccundly, to dletermine whether their synthesis is re-latecl to photomorphogenic processes. The results obtained show that the red/far-red pigment systenm, phytochrome, does in(leed affect both leaf growth atncl KGC biosynthesis sinilarly in peas, although it appears to have little effect on KG biosynthesis. The results provi(le no evidlence that the levels of these kaempferol complexes affect see(dling growth in vivo. Materials and Methods Seeds of Pisum sativumll cv. Alaska, obtaine(d from Associate(l See(l Growers, Inc., New Haven, Con-necticut, were sown in moist washed vermiculite in 10 X 10 X 10 cm polyethylene containers. Each container held about 30 to 40 seedIs. The seedlings were growin in darkness at 27 + 1° and were exposed to dinm green light in the (lark rooml for occasional inspection and again at the tinme of harvesting. Red light was supplied by redl fluorescent tubes (Sylvania, 15 w). The far-red light source consisted of five 300-w internal-reflector incandlescent lamnps, light from whiclh was filteredl through 7 layers each of redl and blue (lu Pont cellophane an(d about 8 cIm1 of water (8). The emission curves for the red