Effects of the Leaf Number, Fruit Number and the Shading of Plants on the Occurrence of Fruit Curvature in Cucumber

Abstract

Causal relationships between the occurrence of fruit curvature and the number of leaves per fruit and shading of plants were investigated with individual plants.
When 1 fruit with 5 leaves attached was retained per plant, fruit showed normal growth and almost no curvature at harvest. On the other hand, fruit with 3 leaves or less was suppressed in growth and showed marked curvature at harvest. In addition, some of them became malformed or aborted.
When 2 or 3 fruit with 6 or 9 leaves (3 per fruit), respectively, were retained per plant, all the fruit showed normal growth and almost no curvature at harvest. When 2 or 3 fruit with 2 or 3 leaves (1 per fruit), respectively, were retained per plant, however, most fruit were suppressed in growth, and showed marked curvature at harvest, while some of them showed relatively normal growth and only slight curvature.
When 1 fruit with leaves, 1, 200 cm² in total leaf area, was retained per plant, fruit showed normal growth and almost no curvature at harvest. On the other hand, fruit with leaves, 800cm² or less in total leaf area, was suppressed in growth and showed marked curvature at harvest.
When 1 fruit was retained per plant, shading with cheesecloth suppressed the fruit growth and increased the fruit curvature angle at harvest. These effects were greater on the fruit with 3 leaves than 5 leaves per fruit.
From these results, it was concluded that the occurrence of the curvature in cucumber fruit was due to the insufficient production of photosynthates and, consequently, their poor supply to the fruit as the results of decreased leaf area, shading, etc.