Geometric Analysis of Seed Shape Diversity in the Cucurbitaceae

Abstract

The Cucurbitaceae is a monophyletic family with close to 1000 species of climbers, including important agronomic species and varieties characterized by tendrils and pepo fruits. The seed’s morphology is varied, and the development and structure of the seed coat have been described in detail on some species. Overall description of the seed shape is based on terms comparing it with geometric figures, but quantitative methods are lacking in the literature. Here we apply a general morphological analysis to seeds of representative genera of the Cucurbitaceae, followed by curvature analysis in the poles and symmetry analysis. These methods are useful for the quantitative description of seed shape and the comparison between species and varieties. Differences between species were found for most morphological measurements, as well as for symmetry and curvature values. The comparison between three species of Cucumis (Cucumis sativus, C. myriocarpus and C. melo) and two varieties of C. melo reveals differences between species and varieties both in curvature and symmetry. The results obtained from both methods, curvature and symmetry analysis, form similar groupings in a cluster analysis. The methods described here were applied for the identification of agronomic varieties and the quantitative description of seed shape in taxonomy.

Seed Morphological Analysis in Species of Vitis and Relatives

“…In our dendrogram, the species of different genera, Ampelopsis aconitifolia, Cissus verticillata, and Parthenocissus quinquefolia, were dispersed among the species of Vitis. From the point of view of shape analysis, it may be interesting to note the increased similarity with Ampelopsis, Cissus or Parthenocissus in the different species of Vitis, as was recently observed in Cucurbitaceae [26]. However, as observed in Cucurbitaceae, these results underscore the limitations of using the J index with geometric models in taxonomy beyond the genus level.…”

“…In addition to overall seed shape description, other quantitative aspects in the analysis of seed morphology comprise the measurement of symmetry and curvature in the apex. Both aspects have been recently applied to seeds of representative species of the Cucurbitaceae [26]. The curvature of a plane curve is a magnitude that measures the rate at which the tangent line turns per unit distance moved along the curve.…”