Biological invasions are a major ecological and socio-economic problem in many parts of the world. Te Beest et al. synthesize current knowledge on the importance of polyploidy for the invasion of introduced plants, and suggest that it may increase the success of plant invaders through a combination of pre-adaptation, where polyploids have a higher survival rate and fitness in the earliest establishment phase, and the possibility for subsequent adaptation due to a larger gene pool. Alternatively, polyploidization may play an important role by restoring sexual reproduction after hybridization or, conversely, allowing for asexual reproduction in the absence of suitable mates.

Population differentiation in a variable environment is related to the selection pressures that plants experience. Ward et al. compare differences in growth- and defence-related traits in two isolated populations of Acacia raddiana trees from sites at either end of an extreme environmental gradient in the Negev desert. They find no evidence of trade-offs between physical and chemical defences and plant growth parameters; rather, there appears to be positive correlations between plant size and defence parameters. The great variation in several traits in both populations may result in a diverse potential for responding to selection pressures in different environments.

Valentine’s Day is here and unless you share the cynics’ view that this is a holiday invented by the flower industry, you might set off to buy a bunch of flowers for your other half on the day. Next time, why not do something completely different this year and create your own unique flowers?

The procedure is very simple (but requires planning ahead!). You will need white flowers and water stained with food colouring. Cut off the flower stems at an angle and leave them in a glass with the dyed water to soak up the fluid over night.

If you are a botany ninja and up for a serious challenge, have a go at creating a rainbow rose. Peter van de Werken (‘River Flowers‘) developed the technique based on his knowledge about plant phyllotaxy. Rose petals are arranged in a  Fibonacci spiral. This means that petal number one and six will be on the same vertical imaginary line. When you cut the stem vertically into four equal parts and transfer each end into a different glass with coloured water, the petals will take up the dye depending on their position in the spiral. Pretty, isn’t it?

“Rainbow Rose” reference: António A. Monteiro, Roberto Lopez and Jules Janick. “Gilding the Lilies: Rainbow Roses and Confetti Poinsettias“. Chronica Horticulturae – Volume 48, Number 1, 2008. 

Photo: Rainbow Rose by Ryan Amos. Licenced under a Creative Commons BY-SA licence.

Assessments of the phylogeny of the green algal class Chlorophyceae using standard, single markers, such as 18S rRNA and rbcL, have generally been unable to match the robust trees produced from analyses of chloroplast genomic data. Buchheim et al. study the orders Chaetophorales, Oedogoniales and Chaetopeltidales and demonstrate that sequence-structure analysis of ITS2 yields results that are largely congruent with those from genomic data. The technique thus provides an economical supplement or alternative to the single-marker approaches used in green algal phylogeny.

Subfamily Hyacinthoideae (Hyacinthaceae) comprises more than 400 species, which show distjunct distribution patterns. Ali et al. use dispersal-vicariance and Bayesian binary MCMC analyses to determine that Hyacinthoideae originated in sub-Saharan Africa. The results suggest a bimodal distribution pattern with sub-Saharan Africa as the primary centre of diversity and the Mediterranean region is the secondary centre. Sub-Saharan Africa was the source area for radiation toward Madagascar, the Mediterranean region and India, whilst radiations occurred from the Mediterranean region to eastern Asia, Europe, western Asia and India

Reproduction imposes a cost as resources are diverted from other functions within the plant. Ida et al. use both defoliation and shading to reduce photosynthate supply in fully pollinated plants of a perennial legume, Oxytropis sericea (Fabaceae), and find that although nectar production is reduced, fruit and seed production are not altered. Allocation of photosynthate to reproductive organs is almost doubled whilst the mass of the taproot declines by almost a third. The insensitivity of fruit and seed production to leaf manipulation is consistent with either compensatory mobilization of stored resources or ovule limitation.

In distylous plant species, skewed morph ratios are not uncommon and may arise from a range of factors such as demographic stochasticity and leakage of the heteromorphic incompatibility system. Meeus et al. study microsatellite variation among 27 Belgian populations of Pulmonaria officinalis (Boraginaceae), and find that, for all genetic measures used, morph bias is more important in explaining patterns of genetic diversity than population size. Significant deviations from equal morph ratios thus not only affect plant reproductive success, but also population genetic diversity of heterostylous plant species.

The extreme complexity of asclepiad flowers (Asclepiadoideae–Apocynaceae) has generated much interest in the pollination biology of this group of plants. Wiemer et al. study pollination mechanisms and pollinators of two South American species, Morrenia odorata and M. brachystephana. The detailed structure of the flowers reveals a complex system of guide rails and chambers precisely arranged in order to achieve effective pollinaria transport, with wasps being the main pollinators. A putative new function of nectar, as a lubricant for pollinaria entering the guide rail, is suggested.

Genome size is known to affect various plant traits such as stomatal size and seed mass but these associations are not well understood for species with very large genomes, which are largely represented by geophytic plants. Veselý et al.  survey genome size across 219 geophytes and find that it is associated with species’ ecology and phenology, and analysis also shows an association with changes in DNA base composition. They suggest that although production of larger cells appears to be an advantageous strategy for fast development in seasonal habitats, the drought sensitivity of large stomata may restrict the occurrence of geophytes with very large genomes to regions not subject to water stress.

Germination timing, a major determinant of fitness, is extremely sensitive to environmental conditions but the physiological mechanisms regulating it are largely unknown. Barua et al. study Arabidopsis thaliana and find that some attributes, such as sensitivity to GA, predict germination responses to multiple seasonal cues while others, such as ABA sensitivity and seed-coat properties, predict responses to specific cues. The physiological mechanism associated with germination responses to specific environments can therefore influence the potential to adapt to novel combinations of environmental factors experienced during colonization or future climate change.