Growth Regulator Activity and Parthenocarpic Fruit Production in Snake Melon and Cucumber Grown at High Temperature1

Abstract

Abstract Snake melon (Cucumis melo var. flexuosus Naud.) set fruit in the greenhouse at 38/27°C (day/night), but Biet Alpha cucumber (C. sativus L.) failed to set fruit, although both set fruit at 27/21°C. Parachlorophenoxyacetic acid (4-CPA) induced parthenocarpic fruit in both species at 27/21°C, but few parthenocarpic fruit were produced at 38/27°C. Lettuce hypocotyl bioassay showed little gibberellin-like activity in the pistils of either species at anthesis, but showed that inhibitors were present in cucumber pistils at 38/27°C. Auxin-like activity (wheat coleoptile bioassay) was abundant in the pistils of both species at anthesis at 27/21°C, but at 38/27°C inhibitors were present, and there was little auxin-like activity.