Among cereal crops, rice is considered the most tolerant to aluminium (Al). However, variability among rice genotypes leads to remarkable differences in the degree of Al tolerance for distinct cultivars. A number of studies have demonstrated that rice plants achieve Al tolerance through an unknown mechanism that is independent of root tip Al exclusion. We have analysed expression changes of the rice ASR gene family as a function of Al treatment. The gene ASR5 was differentially regulated in the Al-tolerant rice ssp. Japonica cv. Nipponbare. However, ASR5 expression did not respond to Al exposure in Indica cv. Taim rice roots, which are highly Al sensitive. Transgenic plants carrying RNAi constructs that targeted the ASR genes were obtained, and increased Al susceptibility was observed in T1 plants. Embryogenic calli of transgenic rice carrying an ASR5-green fluorescent protein fusion revealed that ASR5 was localized in both the nucleus and cytoplasm. Using a proteomic approach to compare non-transformed and ASR-RNAi plants, a total of 41 proteins with contrasting expression patterns were identified. We suggest that the ASR5 protein acts as a transcription factor to regulate the expression of different genes that collectively protect rice cells from Al-induced stress responses.

The pollination process and breeding system of the sympatric Habenaria johannensis, H. macronectar, H. megapotamensis and H. montevidensis was documented for native populations from Rio Grande do Sul, Brazil. All species investigated offer a nectar reward (mean values of total sugars ranging from 18 to 26%) concealed in a spur. Habenaria montevidensis is pollinated by butterflies (Hesperiidae, especially of the genus Urbanus) that carry pollinaria on their eyes; the other three species are pollinated by Sphingidae. Habenaria johannensis is pollinated by the moths Manduca rustica and M. sexta that carry the pollinaria at the base of the proboscis. Habenaria macronectar is pollinated by the moths Eumorpha labrusca and M. cf. lucetius, and these bear pollinaria between the palpi. Habenaria megapotamensis is pollinated by moths of M. cf. lucetius that bear the pollinaria on the proboscis. All species studied are self‐compatible, but pollinator dependent. They also displayed high reproductive success (ranging from 69.48 to 97.40%) and male efficiency factors slightly higher than 1, suggesting that at least one flower was pollinated for each flower acting as pollen donor. At the study sites, the investigated Habenaria spp. are isolated (in terms of pollination) by a set of factors that includes differing floral morphologies, different pollinators and/or different pollinarium placement on the pollinator. © 2012 The Linnean Society of London, Botanical Journal of the Linnean Society, 2012, ••, ••–••.

As a step towards a revision of the sectional classification of Neotropical species of Habenaria, we focus here on section Pentadactylae. In its current delimitation, this is the largest of the 14 New World sections and embraces a group of 34 morphologically heterogeneous species. We expanded the sampling of Neotropical species currently placed in this section and performed Bayesian, maximum likelihood and parsimony analyses using nucleotide sequences from one nuclear (internal transcribed spacer, ITS) and three plastid (matK, trnK intron, rps16-trnK) DNA regions. In addition, morphological features of these species were reassessed. Based on our analyses, we propose that Habenaria section Pentadactylae should be recircumscribed to include only seven species: H. pentadactyla (the type species of the section), H. dutrae, H. ekmaniana, H. exaltata, H. henscheniana, H. megapotamensis and H. montevidensis. Thirty-two species previously assigned to the section grouped within unrelated clades and are therefore excluded from the section. There are no unambiguous morphological synapomorphies for the section, but the group can be confidently recircumscribed and identified on the basis of a combination of diagnostic morphological vegetative and floral characters. Morphological floral features in Habenaria montevidensis are distinct from those of other species in the section, probably as a result of a shift to diurnal pollinators. Following a taxonomic revision of the group, H. crassipes is placed under the synonymy of H. exaltata and neotypes are designated for H. crassipes, H. montevidensis and H. recta (= H. ekmaniana). All species in the section live in marshes or wet grasslands from northern Argentina to central Brazil; most species are concentrated in southern Brazil. Most species are probably rare, and five may be threatened according to the World Conservation Union (IUCN) criteria.

Chloraea membrancea is pollinated by deceit. Together, self-compatibility, pollinarium texture, pollinator abundance and behaviour may account for the observed high fruiting success. It is suggested that a reappraisal and re-analysis of important flower features in Chloraeinae orchids is necessary.