Miscanthus is a perennial energy grass predominantly used for combustion but there is increasing interest in fermenting the cell-wall carbohydrates or green-cutting for soluble sugars to produce bioethanol. Our aims were to: (1) quantify non-structural carbohydrates (NSC), (2) observe the timing of seasonal shifts in the stems and rhizome, and (3) identify developmental and/or climatic conditions that promoted carbohydrate remobilization from the stems to the rhizome during senescence. Two genotypes of Miscanthus sinensis, a Miscanthus sacchariflorus and a Miscanthus × giganteus were grown at replicated field sites in Aberystwyth, West Wales and Harpenden, South East England. NSC were quantified from the rhizome and aboveground organs and then correlated with climatic data collected from on-site weather stations. PAR and maximum daily temperatures were higher at Harpenden throughout the year, but daily minimum temperatures were lower. Senescence was accelerated at Harpenden. Carbohydrates were retained within the stems of nonflowering genotypes, at both sites, in winter and were still present after a frost event to −2°C. Rhizome starch concentrations were at least equal to the previous winter's levels (February 2011) by September. Lower daily minimum temperatures accelerate the rate of senescence and warmer daily maximum temperatures cannot counteract this effect. At current yields, M. × giganteus, could produce 0.7 t ha −1 of NSC in addition to ligno-cellulosic biomass in November but with concerted breeding efforts this could be targeted for improvement as has been achieved in other crops. Shifting harvests forward to November would not leave the rhizome depleted of carbohydrates.

Despite much recent activity in the phylogeny and developmental genetics of grasses, the enigmatic homologies of their reproductive structures remain largely unresolved, partly because their highly derived morphology has resulted in a unique associated terminology. Outstanding questions include whether grass lodicules and stamens are derived from a single perianth or stamen whorl, respectively, whether the grass caryopsis is homologous with a nut, and how the scutellum evolved. We investigated the reproductive structures of the putative sister group of grasses, the southwestern Australian family Ecdeiocoleaceae, which includes two genera, Ecdeiocolea and Georgeantha. The zygomorphic arrangement of the four (rather than six) stamens in male flowers of Ecdeiocolea indicates that they may represent three outer stamens plus the adaxial inner stamen. Within Ecdeiocoleaceae, characters such as the highly unusual nucellus structure of Ecdeiocolea are autapomorphic. Sister-group comparisons indicate that some characteristic grass features, notably the scutellum, do not occur in their putative closest relatives and that more data are needed on early-diverging grass genera to resolve these issues. The grass caryopsis could represent one end of a transformation series embodied by the reduced gynoecial structure and indehiscent fruit of other Poales such as Flagellaria, Joinvillea, and Ecdeiocolea.

Willows (Salix spp.) grown as short rotation coppice (SRC) are viewed as a sustainable source of biomass with a positive greenhouse gas (GHG) balance due to their potential to fix and accumulate carbon (C) below ground. However, exploiting this potential has been limited by the paucity of data available on below ground biomass allocation and the extent to which it varies between genotypes. Furthermore, it is likely that allocation can be altered considerably by environment. To investigate the role of genotype and environment on allocation, four willow genotypes were grown at two replicated field sites in southeast England and west Wales, UK. Above and below ground biomass was intensively measured over two two-year rotations. Significant genotypic differences in biomass allocation were identified, with below ground allocation differing by up to 10% between genotypes. Importantly, the genotype with the highest below ground biomass also had the highest above ground yield. Furthermore, leaf area was found to be a good predictor of below ground biomass. Growth environment significantly impacted allocation; the willow genotypes grown in west Wales had up to 94% more biomass below ground by the end of the second rotation. A single investigation into fine roots showed the same pattern with double the volume of fine roots present. This greater below ground allocation may be attributed primarily to higher wind speeds, plus differences in humidity and soil characteristics. These results demonstrate that the capacity exists to breed plants with both high yields and high potential for C accumulation.

Small-seeded plant species are often reported to have high relative growth rate or RGR. However, because RGR declines as plants grow larger, small-seeded species could achieve higher RGR simply by virtue of their small size. In contrast, size-standardized growth rate or SGR factors out these size effects. Differences in SGR can thus only be due to differences in morphology, allocation, or physiology. We used nonlinear regression to calculate SGR for comparison with RGR for 10 groups of species spanning a wide range of life forms. We found that RGR was negatively correlated with seed mass in nearly all groups, but the relationship between SGR and seed mass was highly variable. We conclude that smallseeded species only sometimes possess additional adaptations for rapid growth over and above their general size advantage.

The reasons why some plant species were selected as crops and others were abandoned during the Neolithic emergence of agriculture are poorly understood. We tested the hypothesis that the traits of Fertile Crescent crop progenitors were advantageous in the fertile, disturbed habitats surrounding early settlements and in cultivated fields. We screened functional traits related to competition and disturbance in a group of grass species that were increasingly exploited by early plant gatherers, and that were later domesticated (crop progenitors); and in a set of grass species for which there is archaeological evidence of gathering, but which were never domesticated (wild species). We hypothesised that crop progenitors would have greater seed mass, growth rate, height and yield than wild species, as these traits are indicative of greater competitive ability, and that crop progenitors would be more resilient to defoliation. Our results show that crop progenitors have larger seed mass than wild species, germinate faster and have greater seedling size. Increased seed size is weakly but positively correlated with a higher growth rate, which is primarily driven by greater biomass assimilation per unit leaf area. Crop progenitors also tend to have a taller stature, greater grain yield and higher resilience to defoliation. Collectively, the data are consistent with the hypothesis that adaptations to competition and disturbance gave crop progenitors a selective advantage in the areas surrounding early human settlements and in cultivated environments, leading to their adoption as crops through processes of unconscious selection.

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Bioenergy crops have a secondary benefit if they increase soil organic C (SOC) stocks through capture and allocation belowground. The effects of four genotypes of short-rotation coppice willow (Salix spp., 'Terra Nova' and 'Tora') and Miscanthus (M. × giganteus ('Giganteus') and M. sinensis ('Sinensis')) on roots, SOC and total nitrogen (TN) were quantified to test whether below-ground biomass controls SOC and TN dynamics. Soil cores were collected under ('plant') and between plants ('gap') in a field experiment on a temperate agricultural silty clay loam after 4 and 6 years' management. Root density was greater under Miscanthus for plant (up to 15.5 kg m −3 ) compared with gap (up to 2.7 kg m −3 ), whereas willow had lower densities (up to 3.7 kg m −3 ). Over 2 years, SOC increased below 0.2 m depth from 7.1 to 8.5 kg m −3 and was greatest under Sinensis at 0-0.1 m depth (24.8 kg m −3 ). Miscanthus-derived SOC, based on stable isotope analysis, was greater under plant (11.6 kg m −3 ) than gap (3.1 kg m −3 ) for Sinensis. Estimated SOC stock change rates over the 2-year period to 1-m depth were 6.4 for Terra Nova, 7.4 for Tora, 3.1 for Giganteus and 8.8 Mg ha −1 year −1 for Sinensis. Rates of change of TN were much less. That SOC matched root mass down the profile, particularly under Miscanthus, indicated that perennial root systems are an important contributor. Willow and Miscanthus offer both biomass production and C sequestration when planted in arable soil.

Miscanthus is a rhizomatous C4 grass of great interest as a biofuel crop because it has the potential to produce high yields over a wide geographical area with low agricultural inputs on marginal land less suitable for food production. At the moment, a clonal interspecific hybrid Miscanthus × giganteus is the most widely cultivated and studied in Europe and the United States, but breeding programmes are developing newer more productive varieties. Here, we quantified the physiological processes relating to whole season yield in a replicated plot trial in Wales, UK. Light capture and conversion efficiency were parameterized for four carefully selected genotypes (M. sinensis, M. sacchariflorus and Miscanthus × giganteus). Differences in the canopy architecture in mature stands as measured by the extinction coefficient (k) were small (0.55–0.65). Sensitivity analysis on a mathematical model of Miscanthus was performed to quantify the accumulative intercepted photosynthetically active radiation (iPAR) in the growing season using (i) k, (ii) variation in the thermal responses of leaf expansion rate, (iii) base temperature for degree days and (iv) date start of canopy expansion. A 10% increase in k or leaf area per degree day both had a minimal effect on iPAR (3%). Decreasing base temperature from 10 to 9 °C gave an 8% increase in iPAR. If the starting date for canopy expansion was the same as shoot emergence date, then the iPAR increases by 12.5%. In M. × giganteus, the whole season above ground and total (including below ground) radiation‐use efficiency (RUE) ranged from 45% to 37% higher than the noninterspecific hybrid genotypes. The greater yields in the interspecific hybrid M. × giganteus are explained by the higher RUE and not by differences in iPAR or partitioning effects. Studying the mechanisms underlying this complex trait could have wide benefits for both fuel and food production.