Annals of Botany 2008 101(5):NP; doi:10.1093/aob/mcn036
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ContentSnapshots
Molcular self-assembly of helicoidal structures (Botanical Briefing)
In the above-ground
phytosphere, the outer epidermal wall of the growing stem forms
a ‘tensile skin’.
Kutschera (pp. 615–621) shows that this sturdy, growth-limiting organ wall is composed
of helicoidally organized cellulose microfibrils. This complex
design evolved independently in peripheral tissues of plants
and animals (e.g. the insect cuticle).
Fire cues do not alter seed coat permeability in Grevillea
Seed dormancy of
some chaparral species is broken by smoke from fires. This alters
seed coat permeability to germination inhibitors. However,
Briggs and Morris (pp. 623–632) find that in
G. linearifolia neither smoke nor heat shock remove
multiple seed coat barriers to the diffusion of apoplastic tracers.
Thriving in harsh environments
The need to maintain
adequate levels of genetic variation is especially strong in
endemic species living in a restricted habitat.
Mameli et al. (pp. 633–640) investigate the genetic structure of endangered
Centaurea horrida by means of microsatellites. A significant amount of variability
is found, which, if correctly managed, will ensure the survival
of the species.
Floral divergence and pollinator preference in Mimulus
Adaptation to pollinators
is thought to drive floral divergence.
Cooley et al.(pp. 641–650) test whether pollinator preference is associated with floral
diversity in four closely related
Mimulus species. Surprisingly,
they find little evidence for pollinator differentiation, suggesting
that factors other than pollinator shifts contribute to floral
diversity in these species.
Phylogeny and conservation of Sinojackia
Sinojackia is a
Chinese endemic genus of the Styracaceae comprising eight species.
The phylogeny and species circumscription in
Sinojackia is problematic.
Yao et al. (pp. 651–659) give the first account of phylogenetic
relationships in
Sinojackia based on molecular and morphological
data. This may help develop successful conservation strategies
for the genus.
Cell wall changes in space
Effects of spaceflight
on xylem anatomy and arrangement of cellulose microfibrils in
vessel walls of soybean are examined by
De Micco et al. (pp. 661–669) using morphometric ultrastructural analyses. They reveal that
cell-wall building is perturbed in space only at early stages
of development. Anatomy is unaltered in more mature structures.
Clonal integration and competitive ability of alligator weed
Clonal integration
may enhance competitive ability of clonal invaders. However,
Wang et al. (pp. 671–678) find the beneficial effects
on alligator weed,
Alternanthera philoxeroides, are minimal
when it competes severely with a neighbour grass. Integration
also fails to affect the relative neighbour effect. Thus, clonal
integration is of little importance for alligator weed under
severe competition.
Precocious flowering and dwarfing in apple trees
Flower initiation
in axillary buds, induced by dwarfing rootstocks and interstocks
during the first year of tree growth, influences types of growth
units and number of growth cycles produced in the second year
(Seleznyova et al ., pp. 679–687). This changes canopy
structure and reduces the vigour of young apple trees.
Acclimation to cold and high light in barley
Rapacz et al. (pp. 689–699) examine effects of cold and high light stress separately and
together on photosynthetic characteristics. They suggest that
accumulation of COR14b protein during cold acclimation helps
protect the photosynthetic apparatus from photodamage especially
during light exposure following freezing.
Mimicking the Australian outback to alleviate seed dormancy
High temperatures
and sporadic rainfall in summer characterize Australia's semi-arid
tropics. By mimicking these conditions,
Hoyle et al. (pp. 701–708) show that dry/wet cycling alleviates physiologically dormancy
of
Actinobole uliginosum,
Goodenia cycloptera and
Velleia glabrata.
In contrast,
Goodenia fascicularis responds more to short periods
of warm stratification.
Impact of human presence on tree species
Species' richness
and human population density are often positively correlated.
At the regional scale in Italy,
Pautasso and Chiarucci (pp. 709–715) show a strong positive correlation between human population
and species' richness of veteran trees. But this relationship
fails to hold for tree abundance at either regional or provincial
levels. Implications for conservation are highlighted.
Sexual dimorphism in an andromonoecious spurge
In the Mediterranean
Euphorbia nicaeensis, male and hermaphrodite cyathia differ
in longevity, size, pollen production and nectar secretion.
Narbona et al. (pp. 717–726) reveal that most differences
between both types of cyathia are the result of positional effects.
Sexual dimorphism based on the gender was found only in the
nectar secretion pattern.
Retaining mechanical strength in the shade
Leaves that develop
in shade must be mechanically strong with minimal investment
in support. With their model, quantifying how leaf anatomical
traits contribute to mechanical strength,
Onoda et al. (pp. 727–736) show that shade leaves are stronger relative to their mass because
they are thinner and have a relatively thick epidermis.
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