An Angiosperm Species Dataset Reveals Relationships between Seed Size and Two-Dimensional Shape

Abstract

Datasets containing information on seed size have been published and are currently available. Nevertheless, there is a lack in the literature of a dataset dedicated to seed shape. We present a preliminary version for a dataset on seed morphology based on a comparison of seed shape with geometric figures. Similarity of the outline of seed images with geometric models is considered as a basis to classify seeds according to the geometric figures they resemble (e.g., ellipse, oval, cardioid). This allows, first, the classification of plant species according to their geometric type of seed, and second, seed shape quantification. For each seed image, the percent of similarity of their outline with a geometric figure can be calculated as a J index. Similarity in absolute terms is considered only when the J index >90. This criterion is important to avoid ambiguity and increase discrimination. The dataset opens the possibility of studying the relationship between seed shape and other variables such as seed size, genome complexity, life form or adaptive responses.

Seed Geometry in the Vitaceae

“…The seeds of the Arecaceae and the Vitaceae present a great diversity, including a combination of forms relatively infrequent in other plant families. Ellipses, ovals and cardioids are geometric forms frequent in plant families [ 18 ]; in contrast, superellipses are not so frequent. These adjust better to intermediate shapes between ellipses and rectangles.…”

“…J index measures the percent of similarity between two images (the seed and the model) and provides information on overall seed shape [ 16 , 17 ]. Bidimensional seed images of many plant species adjust well to one of three morphological types: the ellipse, the oval and the cardioid [ 18 ]. The seeds of the model plant Arabidopsis thaliana (L.) Heynh., those of the model legumes Lotus japonicus (Regel) K.Larsen and Medicago truncatula Gaertn., as well as the seeds of Capparis spinosa L., in the Capparaceae and Rhus tripartita DC.…”

“…A given geometric type is sometimes associated with other morphological or ecological characteristics. For example, cardioid-type seeds were observed to be more frequent in small-sized seeds, while elliptic shape is more frequent in larger seeds [ 18 ]. In the Malvaceae, cardioid type seeds are associated with small herbs of annual cycle [ 29 ].…”

Seed Geometry in the Arecaceae

“…The largest subfamily, the Arecoideae, contains 106 genera grouped into 14 tribes, of which the largest, the Areceae is formed by 11 subtribes mer" (Lodoicea maldivica [J. F. Gmelin] Persoon). The size and shape of fruits and seeds correspond to a diversity of types of dispersion, often in water or by zoochory by a variety of animals [6][7][8][9][10], with a predominance of the circular, ellipsoid, and oval morphology [1,11]. The combinations of fibrous mesocarps and hard endocarps enclosing a cavity made of the fruits of Cocos nucifera L. (Cocoseae, Arecoideae), L. maldivica (Borasseae, Coryphoideae), and other species, adaptations to floating in sea water, while other fruits have fleshy mesocarps and brightly colored epicarps attractive to mammalians such as civets (Caryota maxima Blume; Arenga pinnata [Wurmb] Merr.…”

“…L'Hér. (Myrtaceae), and Peganum harmala L., in the Nitrariaceae [11]. In the Arecaceae, this occurs in diverse genera (Latania, Phytelephas, Salacca .…”