Dust seeds, orchids from two different continents and pollination in S-shaped flower heads – read in latest issue of NJB
Submitted by nordicjbotany on 16 May 2014.Pyrolae dust seeds
Dust seeds are the smallest seeds in angiosperms weighing just about a few micrograms. These seeds are characteristic of most orchids, but in this study the authors examined seed features, seed production and seed dispersal in another plant group with dust seeds, the Pyroleae (Monotropoideae, Ericaceae). Seed production per capsule among the six studied species was in the range between ca 1000 and 7800. Based on the present study, the Pyroleae species were suggested to have a generally efficient pollination system. The investigated Pyroleae species had a seed production comparable to the less fecund orchid species. Seed dispersal in the field was studied in one of the species, P. chlorantha. Despite the extremely small and potentially buoyant seeds, the vast majority of seeds were deposited close to the seed source, within a few meters.http://onlinelibrary.wiley.com/doi/10.1111/j.1756-1051.2013.00307.x/abst...
New orchids from Brazil, Thailand and India
Two new species of Specklinia were found in the northern part of the Brazilian Atlantic Forest, one of the world’s biodiversity hotspots. Specklinia integritepala is a small epiphytic orchid which grows in moist highland forests of Pernambuco state. Specklinia ianthina has purplish flowers and grows low on trees in deciduous dry forests of Bahia state. http://onlinelibrary.wiley.com/doi/10.1111/j.1756-1051.2013.00183.x/abst...
In Thailand, a new Oberonia-species was discovered. Oberonia pygmaea is one of the smallest species of its genus, and this tiny epiphyte grows in hill evergreen forest around 1100 m above sea level. http://onlinelibrary.wiley.com/doi/10.1111/j.1756-1051.2013.00289.x/abst...
The large genus Dendrobium got a new addition in India. Dendrobium tamenglongense is found in subtropical forest in the Tamenglong district in Manipur.
http://onlinelibrary.wiley.com/doi/10.1111/j.1756-1051.2013.00124.x/abst...
Sigmoid corolla and pollination
The S-shaped flowerheads of Oreocharis pumila make sure that only small sweat bees can pollinate its flowers. During flower evolution, attraction of pollinators and successful pollen transfer has led to diversification of floral forms. Most studies in floral evolution focus on the characteristics of flowers with straight corolla tubes. Oreocharis pumila, however, has an unusual form of sigmoid corolla, where the base of the corolla tube is inclined at an oblique angle downwards before the tube bends forward. In contrast to other sigmoid flowers, the sigmoid corolla of O. pumila was not found to favor insect pollinators with long flexible proboscises. A mechanical fit between floral morphology and pollinator was found, in which only small insect visitors with specialized visiting behavior, in this case small sweat bees, are legitimate pollinators. The authors hypothesize that such a corolla has arisen through selection due to inadequate pollination in early spring in the mountainous habitat that O. pumila occupies.http://onlinelibrary.wiley.com/doi/10.1111/j.1756-1051.2013.00105.x/abst...
Root morphology in Juncellus
Summary by Editor in Chief Dr. Torbjörn Tyler
Wetland plants have to be able to adapt to differences in water depth and such plastic adaptive responses may involve both above-ground and below-ground parts. In this new study, changes in root parameters of the widespread Euroasian sedge Juncellus serotinus in response to different water regimes are investigated. It is shown that at water depths of more than 30 cm this species gradually allocates less and less to root growth. With increasing water depth, roots become both shorter and thinner. In addition, while the thickest roots are found 5–10 cm away from the shoot/rhizome in plants grown in less deep water, the root thickness decrease monotonically with distance from the rhizome in plants grown in deeper water. The possible adaptiveness of the observed changes in root morphology are discussed as well as their implications when using this species for wetland restoration.http://onlinelibrary.wiley.com/doi/10.1111/j.1756-1051.2013.01710.x/abst...