125 years of the Annals of Botany
doi:10.1093/aob/mcu220
The Annals of Botany was founded in 1887 and reached its 125th year of publication in 2012. Jackson (pp. 1–18) marks this anniversary in the first of a two-part history of the journal by investigating the first 50 years of its existence. He considers how the journal was started by nine young but already eminent botanists, headed by Sir Isaac Bayley Balfour, and the cultural influences that brought them together. Recently discovered highly personal letters reveal a falling-out, in 1899, between two of the founders that threatened the journal’s future. He also assesses the impact of World War I and analyses the planning of the Annals of Botany ‘New Series’, which appeared 50 years after the journal’s initial founding.
Development of erumpent buds in Echinocereus
doi:10.1093/aob/mcu208
In Cactaceae, the areole is the organ that forms the leaves, spines and buds, and in Echinocereus the buds are erumpent, i.e. they break through the epidermis of the stem adjacent to the areole. Sánchez et al. (pp. 19–26) study 50 species in the genus and find that the areole is sealed by the periderm, and the areole meristem is moved and enclosed by the differential growth of the epidermis and surrounding cortex. The enclosed areole meristem is differentiated in a vegetative or floral bud, which develops internally and breaks through the epidermis of the stem. This is deduced to be an adaptation to protect the meristem and the bud from low temperatures. The anatomical evidence supports the hypothesis that an enclosed bud represents one synapomorphy for Echinocereus.
Disruption of the distylous syndrome in Primula veris
doi:10.1093/aob/mcu211
Flowers of distylous species typically show reciprocal herkogamy and several other polymorphisms. Although distyly has been traditionally described as a discrete floral polymorphism, Brys and Jacquemyn (pp. 27–39) show remarkable habitat-specific variation in flower morphology in populations of the distylous Primula veris (cowslip). In particular, they find strong deviations in stigma length and asymmetric reciprocity levels in several forest populations of the species, especially in L-morph individuals. Surprisingly, these deviations are associated with significant reductions in seed set, indicating that substantial within- and among-population variation in sexual organ reciprocity can have far-reaching ecological and evolutionary implications.
In situ analysis of foliar zinc absorption and movement
doi:10.1093/aob/mcu212
Despite widespread use of foliar-applied Zn fertilizers, much remains unknown regarding the movement of Zn from the leaf surface into the tissues. Du et al. (pp. 41–53) use synchrotron-based X-ray fluorescence microscopy (µ-XRF) to examine absorption of foliar-applied Zn in fresh leaves of tomato (Solanum lycopersicum) and citrus (Citrus reticulatus). They find that once Zn has passed through the leaf surface it appears to bind strongly with limited redistribution, but where movement occurs it is into lower-order veins, with concentrations 2- to 10-fold higher than in the adjacent tissues. Even when it reaches higher-order veins, movement is still comparatively limited, with concentrations decreasing to levels similar to the background within 1–10 mm. The results illustrate the merits of this innovative methodology for studying foliar Zn translocation mechanisms.
Fucosylated xyloglucan in tomato pollen tubes
doi:10.1093/aob/mcu218
In contrast to most eudicots, the fucosyl residues in xyloglucan (XyG) of somatic cells from Solanaceae are replaced by arabinose. Dardelle et al. (pp. 55–66) analyse the cell walls of pollen tubes from wild (Solanum pimpinellifolium, S. peruvianum) and domesticated (S. lycopersicum) tomato, and show that their XyGs are composed of both fucosylated and arabinosylated motifs. The highest levels of fucosylated entities are found in pollen tubes from wild species. The results clearly indicate that the male gametophyte and the sporophyte have different XyG structures, suggesting that the fucosylation of XyG may have an important role in the tip-growth of pollen tubes.
Expansin-like 2 and arabidopsis hypocotyl growth
doi:10.1093/aob/mcu221
Although expansins have been subject to much research, the role and involvement of expansin-like genes/proteins in cell wall metabolism and growth remain mostly unclear. Boron et al. (pp. 67–80) grow transgenic plants of Arabidopsis thaliana and identify lines over-expressing At-EXLA2, a member of the expansin-like A family. They find that over-expression results in an increase of more than 10 % in the length of dark-grown hypocotyls and in slightly thicker walls in non-rapidly elongating etiolated hypocotyl cells. Biomechanical analysis by creep tests shows that At-EXLA2 over-expression may decrease the wall strength in the hypocotyls. They conclude that At-EXLA2 may function as a positive regulator of cell elongation in the dark-grown hypocotyl of arabidopsis by possible interference with cellulose metabolism, deposition or its organization.
AGPs and pectins during pollen development in cork oak
doi:10.1093/aob/mcu223
Arabinogalactan proteins (AGPs) are closely associated with plant reproductive functions. Costa et al. (pp. 81–92) use immunolocalization in male flowers of cork oak, Quercus suber, and find ubiquitous labelling in all cell types with anti-homogalacturan antibodies for methyl-esterified pectins. In contrast, antibodies labelling non-methyl-esterified homogalacturans have a preferential presence in microsporocyte cell walls. Intense labelling is obtained with anti-AGP antibodies both in the tapetum and in the intine, and later in the generative cell wall. A database search identifies four putative AGPs preferentially expressed in the male flower, which probably play a significant role in cork oak reproduction.
Joint analysis of plant growth and development
doi:10.1093/aob/mcu227
Plant growth and development are often studied as two separate processes, but there is structural and functional evidence that the two processes are strongly related. Dambreville et al. (pp. 93–105) study mango, Mangifera indica, and develop a multi-stage model based on absolute growth rate sequences deduced from measurements for given cultivars and growth unit types (either vegetative or flowering), and then they compare developmental stages with growth stages deduced from the model. They find that the growth stages highlight growth asynchronisms between two topologically connected organs, namely the vegetative axis and its leaves. Strong matches are obtained between developmental stages, determined on the basis of morphological changes, and growth stages, leading to a consistent definition of integrative developmental growth stages.
Functional traits and root nitrogen uptake ability
doi:10.1093/aob/mcu233
Leaf functional traits have been used to categorize resource-use specialization, from plants that conserve available resources to those that exploit them, but the contribution of root traits is less well studied. Grassein et al. (pp. 107–115) study N uptake for eight grass species and find that both leaf and root traits can contribute towards differentiating between the two resource-use strategies. Species with high specific leaf area and shoot N content, and low leaf and root dry matter content (RDMC), which are traits associated with the exploitative syndrome, have higher uptake and affinity for both nitrate and ammonium. However, only RDMC and, to a lesser extent, root N content are related to leaf traits, highlighting that root and leaf traits are not necessarily correlated.
Plant trait responses to fine-scale competitive neighbourhoods
doi:10.1093/aob/mcu206
Clonal plants can plastically modify their traits in response to competition, but little is known regarding the spatio-temporal scale at which a competitive local neighbourhood determines the variability in species’ traits. Bittebiere and Mony (pp. 117–126) grow fragments of the rhizomatous Elytrigia repens (Poaceae) in experimental plant communities that vary in species identity and abundance, and find that most of the traits measured respond to the local neighbourhood (5–10 cm radius), with a few additional effects of the wider neighbourhood (20–25 cm radius) also being observed. The temporal influence is not due to the organ lifespan, and most traits respond both to the past and present neighbourhoods. The results demonstrate that plant traits respond to different competitive environments in space and time.
Clonal integration and carbon accumulation capacity
doi:10.1093/aob/mcu207
Enhanced availability of photosynthates increases nitrogen mineralization and nitrification in the rhizosphere via deposition from plant roots. Chen et al. (pp. 127–136) subject clonal fragments of the stoloniferous herb Glechoma longituba with either intact or severed ramets to heterogeneous light environments, and find that the microbial community composition in the rhizosphere of shaded offspring ramets is significantly altered by clonal integration. Increased leaf nitrogen allocation to photosynthetic machinery improves the photosynthetic capability of shaded offspring ramets when the stolon is left intact, suggesting that clonal integration may ameliorate carbon assimilation capacity of clonal plants, thus improving their fitness in temporally and spatially heterogeneous habitats.
Effect of germination time on offspring traits
doi:10.1093/aob/mcu210
Diaspores of heteromorphic species may germinate at different times due to distinct dormancy breaking and germination requirements. Yang et al. (pp. 137–145) determine the effect of germination time of the two seed morphs of Suaeda corniculata on life history traits of the offspring, and find that plants that germinate late in the year have a higher proportion of non-dormant brown than dormant black seeds. They conclude that altering the proportion of the two seed types in response to germination timing can help alleviate the adverse effects of delayed germination, and provide species such as S. corniculata with a flexible strategy that may favour the maintenance and regeneration of populations in unpredictable environments.
Seed bank dynamics and persistence of Brassica hybrids
doi:10.1093/aob/mcu213
Gene flow from crops to their wild relatives has the potential to alter population growth rates and demography of hybrid populations, especially when a new crop has been genetically modified. Hooftman et al. (pp. 147–157) estimate full life-cycle demographic rates of non-GM Brassica rapa × B. napus F1 hybrids and their parent species in both agricultural and semi-natural habitats and model altered fitness potential using periodic matrices, including crop rotations and outcrossing between parent species. They find that hybrid persistence is highly dependent on the seed bank, suggesting that targeting hybrid seed survival could be an important management option. For local risk mitigation, an increased focus on the wild parent is suggested. Management actions, such as control of B. rapa, could indirectly reduce hybrid populations by blocking hybrid replenishment.
Ontogenetic trajectories of foliar terpenes in Eucalyptus
doi:10.1093/aob/mcu222
Foliar terpenes influence a broad range of ecological interactions, including plant defence. Borzak et al. (pp. 159–170) study seedlings of Eucalyptus globulus sourced from different families and genetically distinct populations, representing relatively high and low chemical resistance to mammalian herbivory. They find that foliar terpenes show a series of dynamic changes with ontogenetic trajectories differing between populations and families. Sesquiterpenes change rapidly through ontogeny and express opposing trajectories between compounds, but show consistency in pattern between populations, whereas changing expression in monoterpene trajectories are population- and compound-specific. They hypothesize that these observed genetic-based patterns reflect multiple changes in the regulation of genes throughout different terpene biosynthetic pathways.