Phenological data of a Neotropical savanna community.

Savanna plant species commonly have different adaptive mechanisms in response to fire. In this biome, phenology is a functional trait characterizing the responses of plant communities to fire. The database presented here provides phenological data on 95 angiosperm species, in plots with natural vegetation and/or in burned plots. We used 10 plots (5 × 5 m) installed in "campo cerrado" physiognomy, in the Santa Bárbara Ecological Station, located in the municipality of Águas de Santa Bárbara, São Paulo state, southeastern Brazil. Half of these plots was burned in Aug/2013 and the other half was kept intact as a control. For one year (Sep/2013 to Aug/2014), we collected monthly data on the presence of sprouting (new branches or new unexpanded leaves), flowers (flower buds and flowers at anthesis) and fruits (immature and mature) in all angiosperm individuals present in the plots. This phenological data can support other studies on these sampled species, involving different aspects of their ecology, and on the conservation of this type of vegetation and management plans in relation to the prescription of fire.

A flower with several secretions: anatomy, secretion composition, and functional aspects of the floral secretory structures of Chelonanthus viridiflorus (Helieae-Gentianaceae).

Floral secretory structures have been reported for Gentianaceae; however, morphoanatomical studies of these glands are rare. We described the development and secretory activity of the colleters and nectaries throughout the floral development of Chelonanthus viridiflorus. We collected flower buds, flowers at anthesis, and fruits to be investigated using light and scanning electron microscopy. We performed histochemical tests on the secretion of colleters and used glycophyte to confirm the presence of glucose in nectar. Colleters are located on the ventral surface of sepals and nectaries occur in four regions: (i) the dorsal and (ii) ventral surfaces of sepals; (iii) apex of petals; and (iv) base of ovary. The colleters have a short peduncle and a secretory portion with homogeneous cells. They are active in flower buds and secrete polysaccharides and proteins. In flowers at anthesis, they begin to senescence presenting protoplast retraction, cell collapse, and lignification; these characteristics are intensified in fruit. The nectaries of sepals and petals have two to five cells surrounding a central cell through which the secretion is released. Nectaries are numerous, forming a nectariferous area on the dorsal surface of sepals, like that observed on petals, and can form isolated units on the ventral surface of sepals. They are active from flower buds to fruits. A region with secretory activity was identified at the base of the ovary. The secretion of colleters acts in the protection of developing organs, while nectaries are related to defenses against herbivores and the supply of nectar to potential robbers or pollinators.

Timing of pollen release and stigma receptivity period of Piper vicosanum: New insights into sexual reproduction of the genus.

PREMISE OF THE STUDY: Dichogamy is a common characteristic among angiosperms, including Piper species. In this genus, the tiny flowers are morphologically similar and have an asynchronous stamen development. However, there is no information on the duration of stigma receptivity and whether it overlaps with pollen release. To better understand mechanisms of floral function in Piper vicosanum, we provide a detailed characterization of the timing of pollen release from the four stamens and the period of stigma receptivity and exposure mode of the receptive areas. METHODS: We investigated plants of a natural population in a semideciduous seasonal forest (Viçosa, Minas Gerais State, southeastern Brazil), based on chemical tests, light microscopy, and scanning electron microscopy analyses. KEY RESULTS: Incomplete protogyny-a mechanism that favors outcrossing-was recorded. The period of stigma receptivity was long (14 d), and the sequential exposure and senescence of stigmatic papillae occurred gradually and in a basipetal direction. Pollen release began 2-6 d after the beginning of the pistillate phase, with an average pollen viability of 87.7%, during the bisexual flower phase. Pollen was released for up to 6 d and occurred in one stamen at a time. The fruit set observed in tests of self-pollination indicated self-compatibility. CONCLUSIONS: The gradual and sequential exposure of stigmatic papillae in P. vicosanum flowers is described here as the mechanism for the long duration of receptivity. Anther development and pollen release were also sequential. These findings are yet unreported reproductive characteristics of the genus and offer new perspectives for future studies on the floral biology of other Piper species.