¿Samaras or samaroid fruits? Macroscopic structure of the mature fruits of Myroxylon balsamum (Fabaceae, Papilionoideae)
DOI:
https://doi.org/10.30550/j.lil/2020.57.2/1Keywords:
Balsam, carpology, legume, morphology, SophoreaeAbstract
In the taxonomic descriptions of Myroxylon balsamum it is mentioned that the fruits are samaroids or samaras, but a definition of these concepts is not provided, nor is the assumed classification discussed. In this article, the macroscopic structure of the mature fruits of this species is described and the carpological classification adopted is justified. Observations on the contents of the seed-chamber are also included. Flowers in different stages of development were analyzed. The floral structures were associated with the structures of the fruits. 800 fruits were dissected. The fruits are simple, dry, indehiscent, glabrous, winged and laterally flattened. In a proximal position are the pedicel, calyx, stipe and wing; distally, the seed-chamber, style and stigma. The wing is an extension of the external wall of the gynoecium. The seed-chamber corresponds to the developed ovary; in cross section the parts of the pericarp and the loculum are observed. 92.5 % of the fruits with seed presented one, the remaining 7.5 % presented two. In seedless fruits, the seed-chamber is flattened, the loculum reduced and the mesocarp resin deposits conspicuous. In fruits with seeds, the seed-chamber is subglobose, the loculum is wide and the resin deposits occupy less space. The seeds may be damaged. Although there is no single definition of samara or samaroid fruit, these types have never been treated as equivalents. The fruits of M. balsamum are classified here as samaras; being also valid to consider them winged legumes. To explain the variation found in the content of the seed-chamber, ecological and evolutionary hypotheses must be tested.
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