Multi-loci phylogeny and morphological evidence support the recognition of Januaria (Spermacoceae, Rubiaceae), a new monospecific genus endemic to the North of Minas Gerais (Brazil).

Januaria is described as a new monospecific genus of Rubiaceae, based on material from Januária, northern Minas Gerais, Brazil. The new taxon is endemic to Brazil, occurring in a vegetation type that is known locally as "carrasco", in the southern limit of the Caatinga biome. Morphological (including palynological and SEM analyses) and molecular phylogenetic analyses based on nuclear (ETS, ITS) and plastid (atpB-rbcL, peth, rps16, trnL-trnF) sequence data were performed in the Spermacoce clade (tribe Spermacoceae). The molecular position and morphological features (a unique fruit dehiscence type, and pollen exine with simple reticulum) support Januaria as a new genus, with Mitracarpus as sister group, from which it differs principally in calyx morphology, corolla shape, and fruit dehiscence. Additionally, a further comparison with other morphologically similar genera is presented. We provide a formal description of Januaria, together with a distribution map and comments on its conservation. In addition, a discussion about the Brazilian endemics of the Spermacoce clade is given, also with a key to all the genera of this group present in the country.

Anther structure and pollen development in species of Rubiaceae and anatomical evidence of pathway to morphological dioecy.

we conducted anatomical analysis of anthers with the aim to establish the differences in the development pattern of microsporophytes and microgametophytes between perfect and imperfect flowers in the tribe Gardenieae (Rubiaceae). The species studied were: Tocoyena formosa (monoecious with perfect flowers), Cordiera concolor, Genipa americana, Randia calycina, and Randia heteromera (dioecious with imperfect flowers). Flowers in successive stages of development were collected and fixed. The material was processed and examined using light microscopy and scanning electron microscopy. The present study revealed the stage when pollen is arrested in the functionally pistillate flowers of the dioecious taxa. Based on these observations an evolutionary sequence of changes towards the reduction of non-functional anthers in Rubiaceae is proposed. In addition, we describe and discuss characters that might be of importance in future phylogenetic studies in Rubiaceae (e.g., pollen morphology and its dispersal unit, the presence of orbicules, and a new type of placentoid).

Anatomy and development of the edible fruits of Cordiera concolor (Rubiaceae).

A comprehensive study on the fruit anatomy and development of Cordiera concolor was carried out to establish the origin of the gelatinous tissue surrounding the seeds at maturity. Cordiera currently belongs to tribe Cordiereae, forming part of the species-rich lineage called Gardenieae complex. Most genera of Gardenieae complex has many-seeded fleshy fruits, with seeds usually imbedded in a pulp, which historically was considered of a placental nature. For the histological analyses, fruits at different stages of development were fixed in formalin-acetic acid-alcohol and examined with light microscopy. The endocarp has no woody consistency, it is what classifies a fruit as berry. The pericarp is differentiated into three histological zones: 1) the exocarp, formed of the epidermis and the sub-epidermal tannin cells, 2) the mesocarp, consisting of parenchyma with tannins and druses, and 3) the endocarp, derived from the internal epidermis of the ovary. The placental tissue has little development during the formation of the pericarp. We concluded that the gelatinous tissue surrounding the seeds in the ripe fruit is formed of the mesocarp and endocarp. The present results disagree with the widely accepted conception of the placental origin of the gelatinous pulp surrounding the seeds in Gardenieae Complex species.

Embryology of some flowers of the Gardenieae complex (Rubiaceae).

Different breeding systems occur in the Gardenieae complex (Rubiaceae), from homoecy to dioecy which is present in two tribes, Gardenieae and Cordiereae. As part of a broad project focused on the reproductive anatomy of the species of these two tribes, we described the structural and functional differences of the gynoecium in the different floral morphs and determined the degree of gynoecium development in the staminate flowers. We conducted a comparative anatomical study focused on the gynoecium of one homoecious species (Tocoyena formosa, with perfect flowers) and three dioecious species (Genipa americana, Randia calycina, and Randia heteromera) of Gardenieae and one dioecious species (Cordiera concolor) of Cordiereae. The dioecious species have flowers that are morphologically perfect and functionally unisexual. Flowers in successive stages of development were collected, photographed, and fixed in formalin-acetic acid-alcohol. The material was examined using light microscopy and scanning electron microscopy. The anatomy of the ovary, style, and stigma was analyzed, and megasporogenesis and megagametogenesis were studied. The results achieved in this study, together with previously obtained data of the androecium, show that dioecy originated from homoecy in these species, since the unisexual flowers conserve some characteristics of the perfect flowers. In addition, a new type of ovule for the Rubiaceae family is described.

Androecium anatomy of Isertia laevis, a polysporangiate species of Rubiaceae.

In this study, we performed an anatomical analysis of the polysporangiate anthers and the development of pollen in Isertia laevis (Rubiaceae) with the aim to elucidate the internal structure of these atypical anthers. For this purpose, flowers in successive stages of development were dissected and the anthers were processed for conventional anatomical analysis. The material was examined using light microscopy and scanning electron microscopy. The present study shows that the anthers of Isertia laevis have two thecae divided into multiple microsporangia. This division is due to the presence of transverse and longitudinal septa formed of parenchyma and idioblasts with crystals. The septa appear together with the microsporangia and remain in the mature anther, even developing fibrous thickening. As the anther matures, the idioblasts in the septa accumulate crystals until they break, facilitating the separation of the septa from the outer wall of the theca, and thus apparently assisting the process of dehiscence. The mature anther opens through the longitudinal dehiscence of each theca. In addition to the anatomy of the anther, the development and morphology of the pollen, and the presence of orbicules are described. The structure of the anthers of I. laevis is discussed with other polysporangiate species in the Rubiaceae and angiosperms.