1. Improving crop models in the face of
climate change (Viewpoint)
doi:10.1093/aob/mct016 and 10.1093/aob/
mct130
Crop models need improving for an accurate assessment of
the impacts of climate change on crop productivity. Yin
(pp. 465–475) considers that most existing models are unable
to accommodate photosynthetic acclimation to CO2
concentrations, and therefore tend to overpredict crop responses
to elevated CO2. Strong evidence is provided for the need to
quantify carbon–nitrogen interactions in order to simulate this
acclimation mechanism. This would provide a basis for a
mechanistic framework that models critical physiological
processes and traits in response to other climatic factors and
extreme weather events. In an accompanying article, Kimball
(pp. 477–478) comments on a methodological error in a
previously published report of a free-air CO2 enrichment
(FACE) study that is cited by Yin.
Plant biodiversity conservation in
montane ecosystems (Invited
Review)
doi:10.1093/aob/mct125
Mountain ecosystems are hot spots for plant conservation
efforts because they have high plant diversity as communities
replace each other along altitudinal and climatic gradients, and
they have a high proportion of endemic species. Khan et al.
(pp. 479–501) review the need to integrate different
conservation criteria and methodologies and suggest new
means of assessing anthropogenic pressure on plant
biodiversity at both species and community levels. They
consider plant diversity in mountain ecosystems with special
reference to the western Himalayas, ethnobotanical and
ecosystem service values of mountain vegetation within the
context of anthropogenic impacts, and local and regional plant
conservation strategies and priorities.
Pectin and AGP mapping in
germinating olive pollen
doi:10.1093/aob/mct118
Cell wall pectins and arabinogalactan proteins (AGPs) are
important for pollen tube growth. Castro et al. (pp. 503–513)
study AGPs in olive (Olea europaea) pollen and find that they
are newly synthesized during germination, with production and
secretion being spatially and temporally regulated. They
suggest that galactans may provide mechanical stability to the
pollen tube, reinforcing those regions that are sensitive to
tension stress and mechanical damage, and arabinans and AGPs
may be important in recognition and adhesion properties of the
pollen tube and the stylar transmitting cells, as well as the egg
and sperm cells.
Species coherence in a
cytogenetically diverse sedge
doi:10.1093/aob/mct119
The sedge genus Carex, the most diversified angiosperm genus
of the northern temperate zone, is known for its holocentric
chromosomes and karyotype variability. Escudero et al.
(pp. 515–526) provide the first comprehensive study of
population-level patterns of molecular and cytogenetic
differentiation in the genus. They demonstrate dispersal and
genetic connectivity among populations of the North American
Carex scopariathat differ in chromosome numbers, demonstrating
that cytogenetically variable sedge species can still cohere
genetically. This finding is important to our understanding of what
constitutes a species in one of the world’s largest angiosperm
genera.
Highly conserved B chromosomes in
rye
doi:10.1093/aob/mct121
Supernumerary B chromosomes (Bs) represent a specific type of
‘selfish’ genetic element. As they are dispensable for normal
growth, they generally show polymorphisms among populations.
Marques et al. (pp. 527–534) analyse the distribution and
activity of B-located repeats in cultivated rye, Secale cereale
subsp. cereale, and weedy relatives from seven countries ranging
from Turkey to Japan and find that Bs maintain a similar
molecular structure at the subspecies level. The high degree of
conservation of the non-disjunction control region underlines its
functional importance for the maintenance of B chromosomes.
The conserved structure suggests that although rye Bs
experienced rapidevolutionincludingmultiplerearrangementsat
the early evolutionary stages, this process has slowed
significantly and may have even ceased during its recent
evolution.
Gymnosperm B-sister genes and
ovule/seed development
doi:10.1093/aob/mct124
Seeds are producedbygymnosperms andangiosperms butonly the
latter have an ovary to be transformed into a fruit. Lovsisetto et al.
(pp. 535–544) study B-sister genes from two gymnosperms,
Ginkgo biloba and Taxus baccata, and find that in Ginkgo the gene
is involved in the growth of ovular-derived fleshy fruit. They
functionally characterize the gene by ectopically expressing it in
tobacco. In contrast, the fleshy structure in Taxus derives from an
outgrowth of the ovule peduncle, and the B-sister gene is not
involved in its growth. They suggest that B-sister genes have a
primary function in ovule/seed development and a subsidiary role
in the formation of fleshy fruit-like structures when the latter have
an ovular origin, as observed in Ginkgo.
i
ContentSnapshots Annals of Botany Volume112 Number 3 2013
byguestonAugust14,2013http://aob.oxfordjournals.org/Downloadedfrom

2. Repetitive component of the peanut
A genome
doi:10.1093/aob/mct128
Peanut (Arachis hypogaea) is an allotetraploid (AABB-type
genome) of recent origin. Bertioli et al. (pp. 545–559) study the
evolution of the A genome, focusing on its highly repetitive
component. They find that a substantial proportion of the repetitive
content appears to be accounted for by relatively few long
terminal repeat (LTR) retrotransposons and their truncated copies
or solo LTRs, mostly non-autonomous. The retrotransposons
described are all transcribed, although levels are low. They
conclude that the activity of these retrotransposons has been a very
significant driver of genome evolution since the divergence of the
peanut A and B genomes.
Individual mating patterns in mixed
oak stands
doi:10.1093/aob/mct131
Individual variation in mating patterns may have significant
implications for persistence and adaptation of plant populations,
but field data generally focus on population averages. Using a
Bayesian approach, Chybicki and Burczyk (pp. 561–574)
examine the extent of individual variation of several components
of mating patterns in a mixed stand of Quercus robur and
Q. petraea. They find that there is a great variation in intra- and
inter-specific individual mating preferences, individual pollen
immigration rates and heterogeneity of immigrating pollen. They
show that trees can mate assortatively, with little respect to spatial
proximity. Such selective mating may be a result of variable
compatibility among trees due to genetic and/or environmental
factors.
Carbohydrate storage and
allometric partitioning in juvenile
trees
doi:10.1093/aob/mct132
Biomass partitioning for resource conservation might affect plant
allometry, accounting for a substantial amount of unexplained
variation in existing plant allometry models. Tomlinson et al. (pp.
575–587) compare root carbohydrate storage and organ biomass
allometries for juveniles of 20 savannatree species of different leaf
habit – nine evergreen and 11 deciduous – and find that deciduous
species have greater root non-structural carbohydrate than
evergreens, and lower scaling exponents for leaf-to-root and
stem-to-root partitioning. The data provide strong support for the
hypothesis that deciduous and evergreen trees differ in juvenile
biomass allometries because of differences in allocation to root
storage. Substantial unexplained variation in biomass allometry of
woody species may be related to selection for resource
conservation against environmental stresses, such as resource
seasonality.
Molecular analyses help resolve the
evolution of Platanus
doi:10.1093/aob/mct134
Recent research on the history of Platanus has shown that complex
hybridization phenomena occurred in the central American
species, and its evolutionary history remains unresolved. De
Castro et al. (pp. 589–602) employ sequencing of a uniparental
cpDNA marker ( psbA-trnH(GUG)
intergenic spacer) and
qualitative and quantitative SNP genotyping of biparental nrDNA
markers (LFY-i2 and ITS2) to confirm that hybridization and
introgression events between lineages ancestral to modern central
and eastern North American Platanus species occurred.
Chloroplast haplotypes and qualitative and quantitative SNP
genotyping provide information critical for understanding the
complex history of Mexican Platanus. Compared with the usual
molecular techniques of sub-cloning, sequencing and genotyping,
the real-time PCR assay employed provides a quick and sensitive
technique for analysing complex evolutionary patterns.
HvAACT1 increases Al31
-tolerance
in wheat and barley
doi:10.1093/aob/mct135
Al3+
-activated release of citrate from the root apices of
aluminium-tolerant genotypes of barley is controlled by a MATE
gene named HvAACT1 that encodes a citrate transporter. Zhou
et al. (pp. 603–612) over-express HvAACT1 in wheat (Triticum
aestivum) and barley (Hordeum vulgare) using the maize ubiquitin
promoter, and find that increased expression in both species is
associated with increased citrate efflux from root apices, and that
this enhances Al3+
tolerance in both hydroponic solution and in
acid soil. Genetically modifying barley and wheat to express the
barley gene HvAACT1 gene therefore has potential in helping to
alleviate the effects of aluminium toxicity in acid soils.
Maternal sex effects and inbreeding
depression in Fragaria
doi:10.1093/aob/mct120
Gynodioecy (coexistence of females and hermaphrodites) is a
sexual system that occurs in numerous flowering plant lineages. In
order to understand the maintenance of gynodioecy, Dalton et al.
(pp. 613–621) examine the effect of maternal sex type and
inbreeding depression (IBD) on plant performance across several
resource conditions and life stages in woodland strawberry,
Fragariavesca subsp. bracteata. They find that maternal genotype
and resources influence the magnitude of both maternal sex effects
and IBD, with progeny of females being more likely to germinate
under benign conditions and survive under stress. Cumulative IBD
is low but increases with life stage. Assuming the results are
representative for this long-lived perennial, then neither female
maternal advantage nor IBD are strong enough to maintain
gynodioecy under nuclear models of sex inheritance.
ii
byguestonAugust14,2013http://aob.oxfordjournals.org/Downloadedfrom

3. Carbon budgets in deciduous and
evergreen treeline species
doi:10.1093/aob/mct127
The growth limitation hypothesis proposes that treelines form
becausecarbonsinksaremorerestrictedbylowtemperaturesthanby
carbonsources,butmostsupportingevidencecomesfromevergreen
species. Fajardo et al. (pp. 623–631) examine tree growth and
concentrations of non-structural carbohydrates (NSCs) at four
elevations in six deciduous–evergreen mixed-species forests in the
southern Andes and the Swiss Alps, and find that both foliar
types are sink-limited when faced with decreasing temperatures.
Despitethe deciduoustreespecies havingsignificantlyhigher NSCs
than evergreens, no indication is found of carbon limitation in
deciduous species in the alpine treeline ecotone.
miRNAs responsive to low nitrate
doi:10.1093/aob/mct133
MicroRNAs (miRNAs) play an important role in adaptation of
plants to many stresses including low nitrogen availability.
Zhao et al. (pp. 633–642) identify miRNAs and their targets
in maize (Zea mays) subjected to low-nitrogen stress by
combined analysis of deep sequencing of small RNA and
degradome libraries. Of 85 potentially new miRNAs, 25 show a
more than two-fold relative change in response to low-nitrogen
compared to optimal conditions, and two novel putative
miR169 species are identified. The results will help increase
understanding of the physiological basis for low-nitrogen
tolerance and adaptation in maize.
Plant Cuttings Annals of Botany 112: iii–v, 2013
Available online at www.aob.oxfordjournals.org
News in Botany: Nigel Chaffey presents a round-up of plant-based items from the world’s media
Plant Cuttings has changed . . .
We’re experimenting with a new
format for the Plant Cuttings this
month. Whilst applauding the
eclectic mix of content each issue,
some readers of this column have
expressed concern that inclusion of
thefullcitationswithinthetextspoils
their enjoyment of the news items
because this hinders the narrative
flow. So, balancing the need to
provideevidence-basedsciencecommunicationandreadability,
for this issue, in-text references are replaced with numbers, and
fullercitation(s)appearbelowthenewsitem.Whatdoyouthink?
Is this better? Do let me know – either on Twitter: @NChaffey,
or via e-mail: n.chaffey@bathspa.ac.uk. Thank you.
Image: Wikimedia Commons.
Brachypodium is NOT Arabidopsis(!)
Yes, arabidopsis is a model
organism[1–3]
, but for what exactly?
Many would like us to believe that it
is a model for all things botanical,
i.e. plants. However, with those
organisms newly defined as
‘photosynthetic eukaryotic
organisms, including algae and
possibly cyanobacteria’[4]
, that is a
truly tall order for such a slight
specimen! And arguably an extreme
point of view (although entirely
understandable if one’s past, present
and future employment is tied to research grants using this
beast). And, at the other end of the spectrum, there are those
who espouse the view that arabidopsis is truly only a model for
other arabidopses. Well, adding to the debate, David
Pacheco-Villalobos et al. reveal that interactions between the
plant hormones[5,6]
ethylene and auxin in roots of the
monocot Brachypodium distachyon (‘another’ model
plant[7,8]
) differ to those in roots of the dicot Arabidopsis[9]
.
Wheras lowered levels of auxin in Arabidopsis, which can be
caused by increases in another hormone – ethylene – result in
shorter roots, in Brachypodium increases in ethylene lead to
elevated levels of auxin and longer roots(!). The latter’s
‘inverted regulatory relation between the two hormones’ points
to ‘a complex homeostatic crosstalk between auxin and
ethylene in Brachypodium roots, which is fundamentally
different from Arabidopsis and might be conserved in other
monocotyledons’. So, and as those scientists sagely state,
‘Observationsgainedfrommodelorganismsareessential,yetit
remains unclear to which degree they are applicable to distant
relatives’. And, further complicating the ethylene story – if
suchwasneededatthisstage – ‘Scientistsidentifythousandsof
plant genes activated by ethylene gas’[10]
. Examining
transcriptional response to ethylene, Katherine Chang et al.
have shown that this gaseous plant hormone is involved in an
extensive network of cross-regulation with many other plant
hormones centred around EIN3, a transcription factor that
acts as the ‘master regulator’ of the ethylene signalling
pathway[11]
. Although this work was performed in arabidopsis,
EIN3 orthologs[12,13]
exist in many other plants, so this
study is anticipated to have broader relevance to . . . poplar,
soybean, rice, maize, moss and multicellular algae.
Image: Neil Harris, University of Alberta/Wikimedia Commons.
[1]
http://bit.ly/12QsSbE; [2]
http://bit.ly/182JpPt; [3]
http://bit.ly/10IwGzf;
[4]
http://aobblog.com/2013/07/seb2013-science-with-impact/;
[5]
http://en.wikipedia.org/wiki/Plant_hormone;
[6]
http://www.plant-hormones.info/Index.htm; [7]
John Draper et al.,
Plant Physiology 127: 1539–1555, 2001; [8]
http://1.usa.gov/12lOxIW;
[9]
Pacheco-Villalobos et al., PloS Genetics 9: e1003564, 2013;
[10]
http://bit.ly/14CJRT9; [11]
Chang et al., eLIFE, 2: e00675, 2013;
[12]
http://bit.ly/13w5U0W; [13]
http://bit.ly/12lPhh2.
iii
byguestonAugust14,2013http://aob.oxfordjournals.org/Downloadedfrom