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Gynodioecy is defined by the co-occurrence of females and hermaphrodites. Sex determination in such systems is often cyto-nuclear. McCauley and Bailey (pp. 611–620) review recent studies of gynodioecy, including field studies that address the circumstances that determine female and hermaphrodite fitness, studies of the genetics of sex determination, and models that consider the conditions necessary for persistence of cyto-nuclear polymorphism.
Epidermal phenolic compounds are important for protecting the leaf from damage by natural ultraviolet (UV) radiation. Meyer et al. (pp. 621–633) investigate in vivo the spatial pattern of the epidermal UV-absorbance during oak leaf development by fluorescence imaging. They reveal that, in growing leaves, UV-absorbance varies from cell to cell and reflects the asynchronous development of epidermal cells. (Featured article in ContentSelect on p. v.)
The major economic product of Hevea brasiliensis is a rubber-containing latex. Sucrose is the unique precursor of rubber synthesis and its transporters may play an important role in latex production. Dusotoit-Coucaud et al. (pp. 635–647) clone seven putative full-length cDNAs of sucrose transporters from a latex-specific cDNA library, and show that two isoforms HbSUT1A and HbSUT2A are related to ethylene-stimulated latex production. (Featured article in ContentSelect on p. v.)
Ibicella lutea, Proboscidea parviflora, Cleome droserifolia and Hyoscyamus desertorum are semi-desert species of glandular sticky plants suspected of carnivory. However, Płachno et al. (pp. 649–654) consider that the principal criterion between carnivorous and non-carnivorous plants should be based on whether prey capture and the subsequent nutrient uptake is or is not ecologically important. In these terms only Roridula and Drosophyllum appear to be fully carnivorous.
Lychnophora ericoides (Asteraceae) is an endangered shrub with a disjunct geographical distribution in the Brazilian cerrado. Collevatti et al. (pp. 655–664) find a remarkable differentiation between populations from the south-east and centre of the country, which may represent a climatic relict dating from at least 600 000 years ago before warmer and moister conditions caused population extinctions.
On the Tibetan Plateau, shrubs grow at higher altitudes than trees and hence offer a unique opportunity to expand the dendrochronological database beyond the upper treeline. Liang and Eckstein (pp. 665–670) show the potential of alpine rhododendron, Rhododendron nivale, to reconstruct the environmental history for those regions where dendrochronology has not been applied previously.
Erythrina speciosa is a neotropical tree found in flood-prone habitats. Biochemical, physiological and morphological responses under hypoxic conditions are evaluated by Medina et al. (pp. 671–680) using young individual trees. High levels of γ-aminobutyric acid (GABA) and the presence of some aerenchyma even in root tissues of control plants indicates that seedlings of E. speciosa are ready to cope with flooding episodes.
There are very few existing data on the evolution of intercontinental-dispersed species, particularly in combination with hybridization and polyploidy. In the context of nuclear and chloroplast DNA phylogenies, Dierschke et al. (pp. 681–688) provide GISH and FISH evidence supporting a bicontinental hybrid origin of Australian/New Zealand Lepidium polyploids.
Over ten flowering seasons, Sánchez-Lafuente and Parra (pp. 689–701) show that, despite pollinator preferences for Paeonia broteroi plants with larger flowers, and their greater success at seed production, differences in floral traits and integration among regions cannot be attributed to the action of pollinators. Factors limiting seed germination and survival seem to constrain any rapid spread of these otherwise apparently successful phenotypes.
Fruit development can be sustained by many sources in clonal plants: the floral ramet, nearby non-floral ramets and carbohydrate reserves. Nevertheless, Gauci et al. (pp. 703–713) show that fruit development in Rubus chamaemorus (cloudberry) appears to be source-limited, relying mostly on the carbon fixed by the floral ramet. The rhizome and the developing shoot may even compete with the developing fruit for resources.
Seed longevity in soil is difficult to measure, experiments are time consuming and the scarcity of data on seed decay for rare species hampers conservation efforts. To overcome this, a longevity index based on literature data has been proposed. Saatkamp et al. (pp. 715–724) re-evaluate the accuracy of this index in the light of experimental data from a seed burial experiment with rare and common cereal weeds and find it of limited reliability. Using literature data they show that the index is correlated to seed production but not to experimental seed decay.
Early-generation oak hybrids have a trunk with red veins inherited from the pollen-parent cork oak, Quercus suber, but like the mother-parent holm oak, Q. ilex, they have no cork. Lumaret and Jabbour-Zahab (pp. 725–736) find evidence for bi-directional nuclear introgression in 4 % of plants of both species throughout the range where they overlap. Ancient introgression, shown from palynological records, is likely to have led to replacement of Q. suber chloroplast-DNA by that of Q. ilex in two geographical areas. (Featured article in ContentSelect on p. vi.)
Soil salinity is often heterogeneous, yet the physiology of halophytes has typically been studied with uniform salinity treatments around the roots. Using a split-root system, Bazihizina et al. (pp. 737–745) examine the responses of the halophyte Atriplex nummularia to non-uniform salinity in the root-zone. Their results indicate that having only one half of the roots at high salinity does not affect net photosynthesis, shoot growth or shoot water potential.
Weeds resistant to glyphosate pose a substantial problem for grain growers in parts of the sub-tropical northern Australian grain belt. A modelling approach used by Thornby and Walker (pp. 747–756) predicts the evolution of resistance under selection pressure exerted by a range of typical weed-control strategies, and demonstrates that agricultural decision-making explains within-region differences in real rates of resistance evolution.
The largest flowering plant family, the Orchidaceae, relies on mycorrhizal fungi for germination, growth and survival. Huynh et al. (pp. 757–765) demonstrate that mycorrhizal fungi colonizing the terrestrial orchid, Caladenia formosa, are genetically diverse. The results suggest that our current knowledge of fungal–host specificity may be incomplete due to experimental and analytical limitations. (Featured article in ContentSelect on p. vi.)
In field populations of the white campion, Silene latifolia, fruits are often multiply-sired. Burkhardt et al. (pp. 767–773) measure seed paternity, seed mass, pollen tube growth and stigma wilting, and show that later-arriving pollen has decreased chances of fertilizing the ovules. Thus, multiple paternity must result from pollen carry-over or pollinator visits within short intervals.
Modelling the carbon and water balances of forests generally requires many parameters. Reynolds et al. (pp. 775–784) show that the seasonal pattern of leaf biochemical activity and soil moisture response can be parameterized with straightforward general relationships. The authors propose that the response patterns can be generalized when simulating carbon exchange among deciduous species.
A UK-wide survey of meadows of known ages is used by Warren (pp. 785–788) to establish the relationship between the age of the vegetation and the number of creeping buttercup plants with more than five petals per flower. Each plant with flowers with additional petals in a sample of 100 is found to equate to approximately 7 years. An estimate of the heritability of extra petals suggests that the phenotype results from the slow accumulation of somatic mutations in a species that primarily reproduces vegetatively. (Featured article in ContentSelect on p. vi.)