RPO film effectively promotes fruit quality and yield of cucumber through adjusting greenhouse environment and hormone contents

Light conversion films are crucial for optimizing vegetable crop production in greenhouses, particularly during winter and spring seasons. This study investigated the effects of a europium-based light conversion film (RPO) compared to traditional polyolefin film (PO film, control) on cucumber (Cucumis sativus L.) cultivation, focusing on handle length, yield, and fruit quality in a randomized complete block design with three replications. Results demonstrated that RPO film significantly enhanced multiple light parameters: overall transmittance (8.5% increase), far-red radiation (710–760 nm, 17% increase), red-orange radiation (610–709 nm, 9.8% increase), and blue radiation (440–509 nm, 9.6% increase). The film also increased average light intensity (400–700 nm) by 13% and maximum temperature by 13%. Conversely, it reduced ultraviolet radiation (300–399 nm) by 38%, violet radiation (400–439 nm) by 3.3%, and green radiation (510–609 nm) by 5.7%. The modified light environment substantially improved cucumber production metrics. Handle length ratio decreased by 24% due to reduced cell numbers, while yield increased by 30%. Fruit quality parameters showed significant improvements: soluble protein (25% increase), vitamin C (27% increase), free amino acids (28% increase), and soluble solids (9% increase), with a 35% reduction in organic acid content. Notably, both auxin synthesis gene expression and auxin content in cucumber handles decreased by 87% and 24%, respectively.