ABSTRACT Waltheria encompasses about 60 species distributed in Brazil and Mexico. To improve the palynology of the genus, we analyzed 14 species occurring in the Brazilian State of Bahia. Pollen grains were acetolyzed and examined using light microscopy and scanning electron microscopy. Non-acetolyzed pollen grains were viewed by transmission electron microscopy. The results revealed two general pollen types based on exine ornamentation, such as reticulate and echinate, which are distinct with regard to (1) size and shape, (2) apertural type and number, (3) relative length of ectoapertures, and (4) thickening of the nexine compared to the sexine. An ultrastructural analysis of the pollen wall revealed a continuous foot layer and a compact and discontinuous endexine in most cases. The sexine consisted of heterogeneous columellae, which support a perforated semitectum (echinate type) or the semitectum was composed of perforations and muri-shaped thickening (reticulate type). These results confirm a high degree of pollen dimorphism in Waltheria associated with heterostyly.

Rubiaceae foi representada na flora de Brejinho das Ametistas por dezesseis espécies, as quais foram tratadas palinologicamente no presente estudo: Coccocypselum hirsutum Bartl. ex DC., Cordiera rigida Kuntze, Coutarea hexandra K.Schum., Declieuxia fruticosa Kuntze, Diodella apiculata (Willd. ex Roem. & Schult.) Delprete, D. radula (Willd. ex Roem. & Schult.) Delprete, D. teres Small., Emmeorhiza umbellata K.Schum., Leptoscela ruellioides Hook. f., Mitracarpus baturitensis Sucre., Mitracarpus villosus Cham. & Schltdl., Palicourea rigida Kunth, Psyllocarpus asparagoides Mart., Richardia grandiflora Steud., Staelia aurea K. Schum., Staelia galioides DC. Para análise sob microscopia de luz e eletrônica de varredura, os grãos de pólen foram acetolisados, mensurados, descritos, foto e eletromicrografados. Os grãos de pólen variaram de pequenos a grandes; suboblatos a subprolatos. Inaperturados em P. rigida, colpados, e colporados na maioria das espécies, com número de aberturas variável de três a várias. Exina predominantemente microrreticulada entre as espécies, sendo reticulada (C. hirsutum, C. rigida, P. rigida), birreticulada (D. fruticosa), microequinada-perfurada (C. hexandra), equinado-granulada (R. grandiflora), equinado-granulado-perfurada (D. apiculata e D. teres), e psilada (P. asparagoides). Os resultados mostraram que as espécies são palinologicamente distintas.

The palynology of the following 16 species of Rubiaceae, from Brejinho das Amestistas, was investigated: Coccocypselum hirsutum Bartl. ex DC., Cordiera rigida Kuntze, Coutarea hexandra K.Schum., Declieuxia fruticosa Kuntze, Diodella apiculata (Willd. ex Roem. & Schult.) Delprete, D. radula (Willd. ex Roem. & Schult.) Delprete, D. teres Small., Emmeorhiza umbellata K.Schum., Leptoscela ruellioides Hook. f., Mitracarpus baturitensis Sucre., Mitracarpus villosus Cham. & Schltdl., Palicourea rigida Kunth, Psyllocarpus asparagoides Mart., Richardia grandiflora Steud., Staelia aurea K. Schum., and Staelia galioides DC. The pollen grains were acetolysed to and their morphological characters were analyzed using light and scanning electron microscopy. They varied in size from small to large; were suboblate to subprolate; inaperturate (P. rigida), colpate and colporate in the remaining species, with an aperture number that varied from three to several. The exines were microreticulate in most species, reticulate (C. hirsutum, C. rigida and P. rigida), bireticulate (D. fruticosa), microechinate-perforated (C. hexandra), echinate-granulate (R. grandiflora), echinate-granulate-perforate (D. apiculata and D. teres), and psilate (P. asparagoides). Based on the results, palynological data can be used to distinguish these species.