Pollen Morphology and a New Combination in Tribe Justicieae (Acanthaceae), with Emphasis on Brazilian Species

Abstract

Abstract— Justicieae is one of the largest tribes of Acanthaceae, composed of 2000 species distributed in 100 genera, with highest diversity in the neotropical region. Palynological studies containing several representatives of the tribe are rare, specially species from Northeastern Brazil. The present study aims to differentiate species and evaluate palynological characters in the light of a phylogenetic hypothesis of Justicieae. Eighteen species belonging to six genera were analyzed. Pollen grains were acetolyzed, measured and photographed under light microscopy (LM) and scanning electron microscopy (SEM). Pollen grains are medium to very large in size, isopolar, planaperturate, subprolate, prolate to prolate spheroidal, and two-colporate to three-colporate, or with six pseudocolpi. The exine ornamentation is microreticulate to reticulate with areolae between the apertures in most species. Some species present a cavea in the mesocolpium. The pollen morphology of Justicia chamaedryoides, J. congrua, J. glaziovii, J. thunbergioides, J. sphaerosperma, Pseuderanthemum congestum, and P. modestum are hereby described for the first time. A new combination is also proposed, Thyrsacanthus angustissimus.

Pollen morphology of Acanthoideae species from the Shivalik Foothills in Rajaji National Park (Uttarakhand, India)

“…The findings of this current investigation reveal the strict eurypalynous nature of the subfamily Acanthoideae, aligning with earlier studies on Acanthaceae (Alcantara et al, 2022; Al‐Hakimi et al, 2017; Da Silva Monteiro et al, 2023; Dalawai & Murthy, 2021). The pollen morphological traits within the subfamily exhibit significant variability.…”

“…Pollen morphology of various taxa of family Acanthaceae has been also studied by other researchers from different geographical regions of the world (Alcantara et al, 2022;Al-Hakimi et al, 2017;Da Silva Monteiro et al, 2023;Dalawai & Murthy, 2021;Perveen & Qaiser, 2010;Raza et al, 2020;Rueangsawang et al, 2013;Scotland, 1992aScotland, , 1992bScotland, , 1992cScotland, , 1993. However, work on Indian species of Acanthaceae is very limited, including Gupta and Sharma (1986) and Ghosh and Karmakar (2012).…”

La tribu Justicieae (Acanthaceae) en la región oriental del Nordeste de Brasil

“…Comentarios taxonómicos: Thyrsacanthus angustissimus, especie recientemente combinada a este género por Alcantara et al (2022), es morfológicamente relacionada con las especies de Justicia sección Chaetothylax (Nees) V.A.W. Graham, sin embargo, la morfología de los granos de polen de T. angustissimus es similar a aquella reportada en el linaje Tetramerium (Cortês y Rapini 2011, Alcantara et al 2022). Thyrsacanthus angustissimus se caracteriza por la inflorescencia en espiga, brácteas y bractéolas triangulares, cáliz con tricomas glandulares y corola lila con mácula blanquecina.…”