How orchids feed specialized bee pollinators

A significant proportion of orchids in the subtribe Oncidiinae produce floral oil as a food reward that attracts specialized bee pollinators. This oil is produced either by glands (epithelial elaiophores) or by tufts of secretory hairs (trichomal elaiophores). Although the structure of epithelial elaiophores has been well documented, trichomal elaiophores are less common and have not received as much attention.

Variation in floral morphology in the genus Lockhartia

The flowers of Lockhartia are 5–30 mm in length and lack fragrance perceptible to humans. Oil secretion by flowers of Lockhartia was first reported by Silvera (2002), but the morphology and anatomy of their elaiophores have not previously been studied in detail. A recent paper in Annals of Botany surveys the flowers of 16 species of Lockhartia and shows that all have elaiophores (oil glands) of the trichomal type.

Specialized hairs on the legs or abdomen (but not the mouthparts) of oil-gathering bees are used to collect oils, and the latter are then used as food for larvae. Pollinaria of Lockhartia are small (typically 0·7–1·3 mm long) and their attachment to the bodies of bees has not been reported. This may be due to the fact that the thin stipe collapses upon drying and this obfuscates identification of the pollinarium to generic level. The situation is further exacerbated by the fast-flying and extremely timid nature of oil-collecting bees. As a result, they are much more difficult to capture or observe from short distances than male euglossine bees, for which an abundance of observational data exists.

Blanco, M. A., Davies, K. L., Stpiczyńska, M., Carlsward, B. S., Ionta, G. M., & Gerlach, G. (2013). Floral elaiophores in Lockhartia Hook. (Orchidaceae: Oncidiinae): their distribution, diversity and anatomy. Annals of Botany, 112(9), 1775-1791.

 

VN:F [1.9.22_1171]
Rating: 0.0/5 (0 votes cast)

Morphology of lateral root development – free review article

Morphology of lateral root development

Morphology of lateral root development

The crucial role of roots in plant nutrition, and consequently in plant productivity, is a strong motivation to study the growth and functioning of various aspects of the root system. Numerous studies on lateral roots mostly focus on the physiological and molecular bases of developmental processes. Unfortunately, little attention is paid either to the morphological changes accompanying the formation of a lateral root or to morphological defects occurring in lateral root primordia. The latter are observed in some mutants and occasionally in wild-type plants, but may also result from application of external factors.

A recent free review article in Annals of Botany discusses morphological aspects of lateral branching in roots are analysed, examining studies that have looked at developmental changes in lateral root morphology in order to understand better the process of lateral root development.

Our knowledge of the molecular bases of lateral root initiation and development has increased rapidly within recent decades. Building on these advances, we may try to widen our knowledge of the probable relation between auxin and root system morphology, based in part on the auxin-related mutants whose root growth and development are altered in comparison with wild-type plants. Yet it is important to remember that, as a physical object, the lateral root (as well as other plant organs) also has characteristic physical properties. A change of form of such an object implies either a change in the distribution of mechanical stress or a change in mechanical properties. Direct measurement of both of these remains a challenge, mostly because of technical difficulties. However, the few reports examining the mechanical parameters of tissues of roots show that no challenge in science is so great that it is not taken up.

Szymanowska-Pułka, J. (2013). Form matters: morphological aspects of lateral root development. Annals of botany, 112(9), 1643-1654.

 

VN:F [1.9.22_1171]
Rating: 0.0/5 (0 votes cast)

Spatial and temporal functional changes in alpine summit vegetation are driven by increases in shrubs and graminoids

13080-TR1Classical approaches to investigating temporal and spatial changes in community composition offer only partial insight into the ecology that drives species distribution, community patterns and processes, whereas a functional approach can help to determine many of the underlying mechanisms that drive such patterns. In order to determine the mechanisms that drive changes in plant community composition across spatial and temporal scales, a new study published in AoB PLANTS by Venn et al. used plant functional traits to interpret the results of a repeat species survey across a gradient of five alpine summits in south-east Australia. Vegetation changes were strongly affected by the high and increasing proportion of tall shrubs and graminoids, especially at the lower elevation summits. Several significant relationships between the community trait-weighted mean of different traits and elevation suggest that processes such as competition are influencing vegetation preferentially across the elevation gradient, with shrubs and graminoids driving these patterns.

VN:F [1.9.22_1171]
Rating: 0.0/5 (0 votes cast)