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Malus baccata is an apple rootstock that is highly resistant to low temperature (down to –45 °C) but is sensitive to iron deficiency chlorosis, and is often found in calcareous soils in north China. Xiao et al. (pp. 881–889) determine the subcellular localization and function of an iron regulator gene, NRAMP1, cloned from Malus baccata.
Little is known about domestication processes of vegetables lacking archaeological data. Using ancient Chinese literature, Wang et al. (pp. 891–897) reveal that the domestication process of eggplant in China involved three principal aspects of fruit quality. This indicates that evidence as to modifications in domestication traits can be traced through ancient literature in some civilizations.
Less than 0·5 % (approx. 80 species) of Neotropical Melastomataceae produce flower nectar. These are mostly vertebrate-pollinated, and exhibit several morphological shifts. Verassin et al. (pp. 899–909) determine that nectar release seems to be related to stomata located on stamens and ovary apices that are supplied by large vascular bundles. The distribution of nectary stomata in different lineages suggests that nectariferous flowers have evolved independently within the Melastomataceae.
Both localized population-level effects and shared biochemistry between floral scent and floral colour may contribute to variation in floral scent phenotypes for colour-polymorphic plants. Majetic et al. (pp. 911–922) find that for Hesperis matronalis, biochemistry alone cannot explain floral scent variation; rather, floral scent variation may be better explained by localized biotic and abiotic factors, and/or greater complexity in biochemical associations.
Plants exposed to stress can find shelter under the shade of established plants. However, as found by Valladares et al. (pp. 923–933) for two evergreen shrubs from continental, Mediterranean habitats, beneficial effects of shade can be eclipsed by reduced soil moisture during dry years, which are expected to be more frequent due to climate change in this region.
Although genotypes of the clonal plant Potentilla reptans have shown differences in plastic responses to shade, they do not differ in height when directly competing. Vermeulen et al. (pp. 935–943) find that the most abundant genotypes after 5 years of competition do not capture disproportionally more light per unit mass. This suggests that the competition for light is symmetric between genotypes.
Neotropical pioneers occur preferentially in particular sized canopy gaps. Daws et al. (pp. 945–951) show that seed mass-related differences in germination performance contribute to these distribution patterns. Slow germination and a high sensitivity to limited water availability restrict small-seeded pioneers to small gaps while large-seeded species can geminate in the harsh environment of large gaps.
Plant traits that are characteristic of either low altitude or high altitude environments remain a matter of controversy. Milla et al. (pp. 953–966) suggest that formerly neglected traits, such as architectural or organogenetic characters, may differ consistently among altitudes. They propose that architecture is functionally related to other traits typical to either highland or lowland species.
Greenwood et al. (pp. 967–977) derive a mechanistic model that relates whole-crop N : P ratio to biomass during crop growth with near-optimum levels of nutrients. It has only two constants, one of which is close to the average for freshwater autotrophs. The validity of the model is supported by the results of 38 field experiments on numerous species.
Onobrychis viciifolia responds with increased concentrations of condensed tannin (CT) to simulated attacks by fungi, bacteria or herbivorous insects – regardless of the nutrient status of the plant. Häring et al. (pp. 979–987) thus argue that these results challenge some classical defence theories and suggest that the biosynthesis of CTs is inducible by enemy-derived substances.
Puijalon et al. (pp. 989–996) hypothesize that a continuous water current would induce plastic alterations of clonal architecture among aquatic plants. Plastic responses for clonal traits led to two contrasting strategies to cope with mechanical stress: an escape strategy (e.g. through increased length of creeping stems and spacer lengths) and a resistance strategy (through a denser canopy and enhancement of anchorage efficiency).
The Mediterranean habitat of Populus alba is highly fragmented and has been subject to long-term human interference, so it is not known whether some populations are native or exotic in origin. Using chloroplast and nuclear microsatellites, Brundu et al. (pp. 997–1006) study populations of uncertain origin from the island of Sardinia, and demonstrate that white poplar could be regarded as a floristic relict of the native flora with an unusual prevalence of vegetative spread capable of giving rise to very large monoclonal stands, with a restricted number of genets and unique haplotypes.
The relationships within Sauropus (Phyllanthaceae) are largely resolved, and the genus is closely related to Phyllanthus, Glochidion and Breynia. Pruesapan et al. (pp. 1007–1018) show the Australian and Asian Sauropus species to be distinct clades. Breynia is part of the Asian Sauropus clade. Sauropus/Breynia (to be united) are sister to Glochidion and included in Phyllanthus.
Geographic and temporal variation in the timing of reproduction of a columnar cactus of the Sonoran Desert are studied by Bustamante and Búrquez (pp. 1019–1030). They find considerable intraspecific variation in phenological parameters within and between populations, and report for the first time that climatic variance (several months before flowering) is closely associated with the onset of flowering. Geographic variation in plant size and its effect on individual plant fecundity as well as in flowering time are also considered.
Low reproductive output is often problematic in small populations of self-incompatible plants. In such cases ‘genetic rescue’ is a conservation management option, but there is potential for outbreeding depression. Holmes et al. (pp. 1031–1041) reveal pollinator- and mate-limitation in Grevillea repens and demonstrate that its response to inter-population pollination varies with genetic distance and the genetic and ecological background of the pollen-recipient population.
Floral longevity plays an important role in plant reproduction, but also has its costs. Castro et al. (pp. 1043–1048) observe that flower senescence is activated by pollen receipt but delayed pollination has negative impacts on plant reproductive success. Reduced female fitness associated with long floral life span can constitute a cost of extend longevity, counteracting the selection for longer life spans mediated by pollinator limitation.