Ethylene, Carbon Dioxide, and Anthocyanin Synthesis

Abstract

Ethylene has been shown to influence the biosynthesis of light-induced anthocyanin formation in plants (5, 7, 8, 12). In most studies on physiological activity of ethylene in plants, CO. is reported to interfere with plant response to ethylene (1, 3, 4), and it has been suggested that changes in the concentrations of ethylene and CO, around plant tissue may regulate plant development (9). The purpose of these experiments was to determine whether CO, could modify the effect of ethylene on anthocyanin synthesis. MATERIALS AND METHODS Plant Material. The plant materials used in these studies were as follows: dark-grown seedlings of sorghum, Sorghum vulgare L. cv. DeKalb E57, and turnip, Brassica rapa L. cv. Ferry-Morse Purple Top White Globe; plants of poinsettia, Euphorbia pulcherrima Wildenow cv. Paul Mikkelsen; and cranberries, Vaccinium macrocarpon Ait. cv. Early Black. Seeds of sorghum and turnip were surface sterilized with 0.5% sodium hypochlorite for 10 min and planted on 10 ml of sterile agar in 125-ml Erlenmeyer flasks for germination and growth in the dark as previously described for sorghum (6). Seedlings were grown in the dark for 4 (sorghum) or 2 days (turnip) before using in the experimental treatment. Poinsettia plants were grown from cuttings in the greenhouse with three plants per 14-cm pan at a night temperature of 17 + 2 C for 63 days before treatment. Bracts were showing red color at the initiation of the experimental treatment. For each treatment, three pans of plants were placed in a sealed Plexi-glas chamber (96 cm X 60 cm x 91 cm) in the greenhouse. Cranberries were collected at the white stage (5) from a bog at the Cranberry Experiment Station, E. Wareham. Massachu-setts and stored in the dark in a refrigerator at 4 C until used in the experimental treatment. For treatment, berries of uniform size were surface sterilized with 0.5% sodium hypochlo-rite for 2 min and placed on 10 ml of sterile agar in 125-ml Erlenmeyer flasks. Experimental Procedure. Plant material in Erlenmeyer flasks was treated with ethylene or CO, by sealing the flasks with rubber vaccine caps and injecting ethylene or CO, into the gaseous atmosphere around the plant tissue with a hypo-dermic needle and syringe (5, 7). Ethylene and CO2 were added to the Plexiglas chambers containing the poinsettias through a rubber vaccine cap placed in a hole in the chamber side. Erlenmeyer flasks, containing sorghum, turnip, or cranberry plant tissue as controls, had cotton plugs to prevent airborne contamination and to allow free air exchange. The poinsettia control plants were sealed like the treated plants in a Plexiglas chamber, but no ethylene or CO, was added to the chamber. All chambers containing poinsettia plants were opened three times a week for air exchange and watering. Ethylene and CO2 concentrations were re-established after each opening.