Morphological study of fruits, seeds and embryo in the tropical tribe Dipterygeae (Leguminosae-Papilionoideae)

Abstract

This work analyses and describes fruit, seed and embryo morphology of 12 Dipterygeae species. The fruit is quite distinct among genera, being a legume in Taralea, a drupoid legume in Dipteryx and a cryptosamara in Pterodon. It was observed that the three genera present distinct morphological characteristics in the epicarp, mesocarp and endocarp. These structures are strongly associated with the dispersal syndromes presented by the genera. Embryonic descriptions are provided for the first time in this manuscript for the three genera presented here and the main diagnostic characteristics are: (1) a gradual extent of development of the hypocotyl-radicle axis from Taralea (undeveloped) to Dipteryx (the most developed); (2) the plumules are entire in Taralea and pinnate in Dipteryx and Pterodon; (3) a cleft below the hypocotyl-radicle axis in Taralea, absent in the other genera, because of the strongly cordate base of the cotyledonar leaves; (4) differences in the degree of development of the hypocotyl-radicle axis between D. alata, D. rosea and D. micrantha. Dipterygeae presents a noticeable diversity of fruit, seed and embryo, Taralea being the most distinct of all. The results of this morphological analysis suggest an evolutive path for the diaspores in the clade, based on phylogenetic studies which show Taralea as sister to the clade constituted by Dipteryx and Pterodon. Key words: diaspores, dispersion, taxonomy, Fabaceae. ResumoO presente trabalho analisa e descreve a morfologia de frutos, sementes e embriões de 12 espécies de Dipterygeae. O fruto é consideravelmente distinto entre os gêneros, sendo um legume em Taralea, um legume drupoide em Dipteryx e uma criptossâmara em Pterodon. Foi observado que os três gêneros apresentam características morfológicas distintas no epicarpo, mesocarpo e endocarpo. Essas estruturas são fortemente associadas com as síndromes de dispersão apresentadas pelos três diferentes gêneros. Descrições completas dos embriões são apresentadas pela primeira vez neste manuscrito para os três gêneros e as principais características diagnósticas encontradas são: (1) um gradual desenvolvimento do eixo hipocótilo-radícula de Taralea (não desenvolvido) a Dipteryx (bem desenvolvido); (2) as plúmulas são inteiras em Taralea e pinadas em Dipteryx e Pterodon; (3) uma fenda abaixo do eixo hipocótilo-radícula em Taralea, ausente nos outros dois gêneros, devido à base fortemente cordada das folhas cotiledonares; (4) diferenças no grau de desenvolvimento do eixo hipocótilo-radícula entre D. alata, D. rosea e D. micrantha. Dipterygeae apresenta uma notável diversidade de frutos, sementes e embriões, sendo os mais distintos encontrados em Taralea. Os resultados destas análises morfológicas sugerem um caminho evolutivo para os diásporos dentro do clado, com base nos estudos filogenéticos que apontam Taralea como irmã do clado constituído por Dipteryx e Pterodon. Palavras-chave: diásporos, dispersão, taxonomia, Fabaceae.

Floral ontogeny in Dipterygeae (Fabaceae) reveals new insights into one of the earliest branching tribes in papilionoid legumes

“…Diagnostic characters for each genus of Dipterygeae have been investigated by various authors (Polhill, ; Barroso et al ., ; Oliveira & Paiva, ; Francisco, ; Pinto et al ., ). Representatives of Dipteryx are characterized by asymmetric leaflets as a result of the eccentric primary vein (Francisco, ), a drupaceous fruit (Barroso et al ., ; Francisco, ; Pinto et al ., ), seeds with a coriaceous testa, a hilum in lateral or subapical position and a rugose embryo with conspicuous plumule (Francisco, ; Pinto et al ., ).…”

“…Diagnostic characters for each genus of Dipterygeae have been investigated by various authors (Polhill, ; Barroso et al ., ; Oliveira & Paiva, ; Francisco, ; Pinto et al ., ). Representatives of Dipteryx are characterized by asymmetric leaflets as a result of the eccentric primary vein (Francisco, ), a drupaceous fruit (Barroso et al ., ; Francisco, ; Pinto et al ., ), seeds with a coriaceous testa, a hilum in lateral or subapical position and a rugose embryo with conspicuous plumule (Francisco, ; Pinto et al ., ). In Pterodon , the leaf rachis is exalate (Francisco, ), the fruit is a cryptosamara with oil glands in the epicarp (Polhill, ; Barroso et al ., ; Francisco, ; Pinto et al ., ), the seed testa is smooth and the raphe is apparent, with the hilum in a lateral position covered by an aril and a smooth embryo (Francisco, ; Pinto et al ., 2014).…”

“…Representatives of Dipteryx are characterized by asymmetric leaflets as a result of the eccentric primary vein (Francisco, ), a drupaceous fruit (Barroso et al ., ; Francisco, ; Pinto et al ., ), seeds with a coriaceous testa, a hilum in lateral or subapical position and a rugose embryo with conspicuous plumule (Francisco, ; Pinto et al ., ). In Pterodon , the leaf rachis is exalate (Francisco, ), the fruit is a cryptosamara with oil glands in the epicarp (Polhill, ; Barroso et al ., ; Francisco, ; Pinto et al ., ), the seed testa is smooth and the raphe is apparent, with the hilum in a lateral position covered by an aril and a smooth embryo (Francisco, ; Pinto et al ., 2014). Representatives of Taralea have a black and rugose petiolule, an elliptical, hairy ovary (Francisco, ), a legume with elastic dehiscence (Polhill, ; Barroso et al ., ; Francisco, ; Pinto et al ., 2014) and a circular, oval, compressed seed with a basal hilum; the embryo displays a cleft below the radical–hypocotyl axis and an inconspicuous plumule (Barroso et al ., ; Francisco, ; Pinto et al ., ) (see Table ).…”

Sucupira-branca (Pterodon - Fabaceae): does wood anatomy support the distinction among species and hybrid?

“…Pterodon is a genus of arboreal species distributed in South America in Brazil and Bolivia (Pinto et al 2014;Tropicos.org 2021). The natural high resistance of Pterodon wood to xylophagous organisms makes this genus a good candidate for being used in civil construction and fences (Mainieri & Chimelo 1989).…”