Summary Crassulacean acid metabolism (CAM) is a specialized mode of photosynthesis that features nocturnal CO2 uptake, facilitates increased water‐use efficiency (WUE), and enables CAM plants to inhabit water‐limited environments such as semi‐arid deserts or seasonally dry forests. Human population growth and global climate change now present challenges for agricultural production systems to increase food, feed, forage, fiber, and fuel production. One approach to meet these challenges is to increase reliance on CAM crops, such as Agave and Opuntia, for biomass production on semi‐arid, abandoned, marginal, or degraded agricultural lands. Major research efforts are now underway to assess the productivity of CAM crop species and to harness the WUE of CAM by engineering this pathway into existing food, feed, and bioenergy crops. An improved understanding of CAM has potential for high returns on research investment. To exploit the potential of CAM crops and CAM bioengineering, it will be necessary to elucidate the evolution, genomic features, and regulatory mechanisms of CAM. Field trials and predictive models will be required to assess the productivity of CAM crops, while new synthetic biology approaches need to be developed for CAM engineering. Infrastructure will be needed for CAM model systems, field trials, mutant collections, and data management.

Among several candidate perennial taxa, Miscanthus  giganteus has been evaluated and promoted as a promising bioenergy crop. Owing to several limitations, however, of the sterile hybrid, both at the taxon and agronomic production levels, other options need to be explored to not only improve M.  giganteus, which was originally collected in Japan, but to also consider the development of other members of its genus, including Miscanthus sinensis, as bioenergy crops. Indeed, there is likely much to be learned and applied to Miscanthus as a bioenergy crop from the long history of intensive interaction between humans and M. sinensis in Japan, which in some regions of the country spans several thousand years. Combined with its high amount of genetic variation, stress tolerance, biotic interactions with fauna, and function as a keystone species in diverse grasslands and other ecosystems within its native range, the unique and extensive management of M. sinensis in Japan as a forage grass and building material provides agronomists, agroecologists, and plant breeders with the capability of better understanding this species in terms of potential contribution to bioenergy crop development. Moreover, the studies described in this review may serve as a platform for future research of Miscanthus as a bioenergy crop in other parts of the world.

We investigated interactions between plant roots, protozoa and nematodes after addition of patches containing inorganic or organic nitrogen in order to determine whether root proliferation could explain the capture of N by the plant from the patch. Decomposition of a "&N\"$C, dual-labelled, organic patch in the absence of plant roots was also examined. In the decomposing patch the amounts of "$C and "&N remaining co-varied and both declined with time. Nematode numbers increased. However, protozoan biomass and inorganic N (NO $ − and NH % + ) availability did not significantly alter as decomposition of the patch progressed. Addition of inorganic N patches, as NH % NO $ solutions, to the first lateral to emerge from the main seminal root axis of Lolium perenne L. seedlings had no effect on root growth compared with controls 16 d after addition. Protozoan biomass increased. Furthermore, log protozoan biomass and NO $ − concentrations of the growth medium were significantly (P 0n05) and positively related. Plant response (i.e. biomass production, N capture and root length) to an added organic patch was examined using five different grass species (Festuca arundinacea L., Phleum pratense L., Poa pratensis L., Dactylis glomerata L. and L. perenne). Total plant biomass was significantly (P 0n05) repressed by an organic patch. Plant N content was reduced when an organic patch was present but N concentrations were greater. Roots were generally slow to proliferate within the patch but there was a significant (P 0n05) speciesipatch interaction for root length within the patch at harvest and in the 2-cm band below it. However, "&N capture by the plants was not related to mean root length duration. All species captured similar amounts of "&N (c. 3-5 %) at harvest as a percentage of the initial "&N added in the organic patch. Similarly, the percentage of the total N captured from the patch was not related to the proportion of the root weight within the patch. The fraction of the captured N from the organic patch as a percentage of the plants' total N, however, did differ among species. Substantial amounts ( 62 %) of the "&N initially added remained in the patch at harvest. Much less (c. 13-21 %) "$C remained in the patch. Protozoan biomass and nematode numbers increased significantly (P 0n05) in the organic patch, although the relationship between the two groups was not significant. As in the inorganic N study, the relationship between log protozoan biomass and NO $ − concentrations in the soil was significantly positive. We conclude that, when grown in monoculture, plants' N capture from an organic patch is not a simple function of root proliferation. External factors, not plant attributes, are more important in controlling patch exploitation.

In this review, we synthesize the current knowledge of the ecology and impacts of Rhamnus cathartica L., a shrub from Europe and Asia that is a successful invader in North America. Physiological studies have uncovered traits including shade tolerance, rapid growth, high photosynthetic rates, a wide tolerance of moisture and drought, and an unusual phenology that may give R. cathartica an advantage in the environments it invades. Its high fecundity, bird-dispersed fruit, high germination rates, seedling success in disturbed conditions, and secondary metabolite production may also contribute to its ability to rapidly increase in abundance and impact ecosystems. R. cathartica impacts ecosystems through changes in soil N, elimination of the leaf litter layer, possible facilitation of earthworm invasions, unsubstantiated effects on native plants through allelopathy or competition, and effects on animals that may or may not be able to use it for food or habitat.