A Developmental Analysis of Inherited Shape Differences in Cucurbit Fruits

Abstract

Fruit shape in the Cucurbitaceae is inherited, and there are at least four quite distinct types of shape determination, as follows: (1) Differences in shape index (ratio of length to width) which are established in the earliest visible primordia and may persist unchanged throughout development. (2) Constant differences in growth rate between length and width which occur during the entire course of development, causing a progressive change in index. The relative growth of these two dimensions may be measured by a constant. In the types studied this varies from .8 (length growing .8 times as fast as width) to 2.2 (length growing 2.2 times as fast as width). (3) Differences in shape index at maturity which necessarily result from differences in size in all cases where the relative-growth constant is other than 1. Where shape index is progressively changing, the point at which growth of fruit stops (its mature size) will affect its index. (4) Differences in pattern or profile, which are more complex than thos...