Annals of Botany 2009 104(1):i; doi:10.1093/aob/mcp143
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Sucrose-mediated translational control (Botanical Briefing)
Environmental factors
greatly impact plant gene expression and concentrations of cellular
metabolites such as sugars and amino acids.
Hummel et al. (pp. 1–7) discuss the role of sucrose signalling in the translational
control of bZIP11 and the regulation of ribosomal biogenesis
in response to metabolic changes and stress conditions.
Nitric oxide differentially regulates nitrate reductase activity
Nitric oxide (NO)
is an indispensable signal molecule involved in various physiological
functions, and may regulate the activity of nitrate reductase
(NR) in plant roots.
Jin et al. (pp. 9–17) show that a
low concentration of NO stimulates NR activity of tomato roots,
and increasing NO concentration increases NR activity in roots
fed with 0·5 m
M nitrate but decreases it at 5 m
M nitrate. (
Featured article in ContentSelect on p. iii.)
Genome-specific chromosome stability in Brassica
Ge et al. (pp. 19–31) demonstrate that the chromosomes belonging to the three different
genomes in synthetic
Brassica allohexaploids show contrasting
stabilities in crosses with
Orychophragmus violaceus where chromosomes
are eliminated. This is thought to be affected by nucleolar
dominance, with only rRNA genes from
B. nigra being expressed
in all allohexaploids and complex hybrids.
Host mating system and effects of nectar-robbing
When studying the
widespread phenomenon of nectar-robbing and its consequences,
Zhang et al. (pp. 33–39) find that attention needs to
be paid to the mating system of the host plants. Examining nectar-robbing
by
Bombus pyrosoma among three sympatric host species of
Corydalis,
they find that it can have variable effects on female plant
reproduction, which can be explained, at least in part, by whether
the species is an obligate or facultative outcrosser.
Pollination syndromes in African Marantaceae
Within the species
of Marantaceae characterized by an explosive pollination mechanism,
Ley et al. (pp. 41–56) describe four distinct floral syndromes
in Africa (approx. 40 species). Their detection of a diverse
pollinator fauna, including first records of bird-pollination
in these species, and observations of specific adaptations between
flowers and pollinators lead to the hypothesis that pollinators
have played an important role in the speciation of this family.
Seed longevity is related to embryo size and climate of origin
Probert et al. (pp. 57–69) report that seed longevity in air-dry storage is correlated
with seed structure and climate of origin. Rapid ageing of 195
diverse species indicates that seeds with small embryos from
cool, moist regions tend to be shorter-lived than seeds with
large embryos from warm, dry regions. This understanding will
improve the management of conservation collections. (
Featured article in ContentSelect on p. iii.)
Demographic–genetic study of a clonal herb
In order to gain
a better understanding of clonal life-history,
Araki et al. (pp. 71–79) explore demography, growth patterns and spatial distributions
of ramets within genets for a rhizomatous clonal herb,
Convallaria keiskei. Field monitoring of genotypically identified ramets
demonstrates that ramet performance regulates genet dynamics
and distribution, which are different among genets.
Sexuality cannot be replaced by apomixis
Apomixis may be transferred
into sexual populations via the pollen function.
Hörandl and Temsch (pp. 81–89) test this hypothesis by experimental crossings of diploid sexual
plants and polyploid apomictic pollen donors of the
Ranunculus auricomus complex. Flow cytometric seed screening reveals that
introgression of apomixis is inhibited by seed abortion and
also by induced selfing (mentor effects) of sexual individuals.
Sexuality cannot be replaced by apomixis.
Phytolith identification in Mozambican trees
The preservation
of phytoliths in fossil records makes them a tool to study early
plant communities, with ancient types being compared with living
morphotypes.
Mercader et al. (pp. 91–113) examine samples
from 90 species from Mozambique, producing the most extensive
phytolith key for any African ecoregion. Local woody species
are hypervariable silica producers and their phytolith morphotypes
are highly polymorphic; nonetheless, some have taxonomic significance
in a number of families and orders.
Ageing effects in an iteroparous plant species
Ageing effects may
be due to dysfunction, but other causes cannot be excluded in
plants.
Van Dijk (pp. 115–124) shows that in sea beet,
Beta vulgaris, a species with a variable life span, there is
a decline in seed production and root growth in the last year
of life, whatever the life span, but that plants flower about
1·3 days later each year over their whole lifetime. (
Featured article in ContentSelect on p. iv.)
Molecular systematics of Gagea and Lloydia
Zarrei et al. (pp. 125–142) present phylogenetic analyses for 142 in-group taxa of
Gagea and
Lloydia (Liliaceae) using nrITS and plastid sequences. The
results support the monophyly of
Gagea/
Lloydia collectively
and provide the basis for a new classification of
Gagea. Incongruence
between plastid and nrITS trees is potentially due to ancient
hybridization and/or paralogy of ITS rDNA.
Phylogenetics and lineage differentiation of Olea
Besnard et al. (pp. 143–160) report a comprehensive phylogeny of the olive genus, and find
that polyphyly indicates the necessity of revising the current
taxonomic boundaries of
Olea. Phylogenetic dating indicates
that the main lines of evolution in this genus were promoted
by major Tertiary climatic shifts; in particular, diversification
within the olive section (characterized by a dense abaxial indumentum)
was concomitant with the aridification of Africa in the Late
Miocene.
Phylogeny correlates with genome size in hawkweeds
Nuclear genome size
variation is studied within a phylogenetic framework in
Hieracium subgen.
Hieracium (Asteraceae) by
Chrtek et al. (pp. 161–178).
They find that species of western-European origin have significantly
lower genome size than those of eastern-European origin, which
correlates with two major phylogenetic clades based on ETS sequences.
Water-use responses to CO2 in a warm polar environment
Coniferous forests
populated polar regions 140–50 million years ago when
atmospheric CO
2 was at least double that of the present-day.
Llorens et al. (pp. 179–188) investigate how the interaction
between a CO
2-rich atmosphere and variations in daylight might
have influenced water use of these conifers. Although plant
water-use efficiency is improved by CO
2-enrichment, transpiration
is relatively insensitive to atmospheric CO
2. (
Featured article in ContentSelect on p. iv.)
Measurement of Al uptake by fluorescent lifetime imaging
Measuring the aluminium
uptake rate across the plasma membrane of intact root cells
is crucial for understanding the mechanisms and time course
of Al toxicity in plants, requiring high spatial and temporal
resolution.
Babourina and Rengel (pp. 189–195) find that
fluorescent lifetime imaging analysis of the fluorescence of
Al–lumogallion complexes can be used to reliably quantify
Al uptake in the cytoplasm of intact root cells of
Arabidopsis during the initial stages of stress.
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