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Switchgrass (Panicum virgatum L.) shows great bioenergy potential and provides multiple ecological services. However, its severe seed shedding causes biomass waste and seed diffusion risk. Questions arise as to the production performance of switchgrass after panicle removal (PR), which remains unknown. We revealed switchgrass growth responses to PR and illustrated physiological reasons. Compared to the untreated switchgrass, PR significantly stimulated stem elongation (32.13%) and increased tiller number (39.70%), as well as aboveground biomass (24.69%). Importantly, PR significantly increased contents of nonstructural carbohydrates (NSCs) in the stem, which was directly beneficial to the ethanol conversion, and in the rhizome and root. The chlorophyll contents, net photosynthetic efficiency, and photochemical quantum efficiencies of flag leaf increased significantly. PR switchgrass allocated more assimilates into the stem, root, rhizome, and NSCs. Activities of phosphoenolpyruvate carboxylase, ribulose-1, 5-diphosphate carboxylase, sucrose phosphate synthase (SPS) in flag leaf and adenosine diphosphate glucose pyrophosphorylase (AGPase) and SPS in the stem and rhizome all increased significantly. In contrast, activities of the AGPase in flag leaf and sheath decreased significantly. Contents of zeatin nucleoside, gibberellins, and indoleacetic acid in flag leaf, stem, and rhizome all increased. Abscisic acid contents in flag leaf and stem decreased significantly while increased significantly in the rhizome. In conclusion, growth-promoting hormones delayed plant senescence, enhanced leaf photosynthesis, and enhanced vegetative growth through regulating assimilates-metabolism-related enzymes, which increased biomass accumulation in PR switchgrass. This work provided new insights for yield and digestibility improvement in switchgrass through field management practices, hormones regulation, or genetic modification strategies. [Display omitted] • Panicle removal (PR) retarded plant senescence in switchgrass. • PR increased biomass dry weights of switchgrass. • PR increased contents of nonstructural carbohydrates in stem, root and rhizome. • AGPase and SPS facilitated storage and transport of C assimilates in PR switchgrass. • Growth promoting hormones played critical roles in delaying plant senescence. [ABSTRACT FROM AUTHOR]

• Vegetated ditch can effectively intercept nitrogen in farmland runoff. • The 15N stable isotope tracer method was used to analyze the fate of vegetated ditch intercepting farmland runoff nitrogen. • The nitrogen remaining in the L. perenne and E. repens ditch beds was almost completely absorbed by the plants after 60 d of growth. During periods of heavy precipitation, farmland drainage ditches are the main routes for farmland nitrogen flowing into surface waters in northern China. Vegetated ditches can be engineered to mitigate N loss from agricultural runoff. We used a simulation study to evaluate the interception of nitrogen in a ditch without vegetation and three vegetated ditches. The 15N stable isotope tracer method was used to analyze the fate of ditch intercepting farmland runoff nitrogen. The three vegetated ditches were planted with Lolium perenne L., Bromus inermis Leyss. and Elytrigia repens (L.) Nevski. The results showed that the interception rates of nitrogen in the three vegetated ditches were higher than in the ditch without vegetation. The L. perenne ditch had the lowest interception rates of nitrogen among the three vegetated ditches. The interception of nitrogen by the three vegetated ditches was primarily achieved by the capture of nitrogen runoff in the soil ditch bed, which allowed water infiltration. Nitrogen retained in the ditch bed soil of the ditch without vegetation was enriched in the 0–10 cm soil layer from surface mainly. However, in the three vegetated ditches, it was transported to the 50 cm soil layer. All of the nitrogen retained in the vegetated ditches was absorbed by the L. Perenne and E. repens , and the interception of nitrogen was affected by plant species and growth stage in the vegetated ditch. [ABSTRACT FROM AUTHOR]

Switchgrass ( Panicum virgatum L.) has been developed into a major herbaceous bioenergy crop for the production of cellulosic biofuels in North America and many counties in European. As cultivar selection has a major impact on the ultimate biomass productivity, we evaluated the adaptability and yield potential of 12 switchgrass cultivars including both upland and lowland ecotypes from 2010 to 2013 in the Beijing region, Northern China. Plant height was measured after anthesis, but phytomer number and tiller density were investigated at harvest. One single autumn harvest was carried out each year and biomass yields were determined. It was found that the lowland cultivars ‘Alamo’, ‘Kanlow’ and ‘NewYork’ produced the most biomass for their better performances in number of phytomers per tiller and mass per phytomer, though upland cultivars had higher tiller density. ‘Cave-in-rock’ and ‘Trailblazer’ had better biomass production among the upland cultivars and they were also recommended for planting together with lowland ones for their excellent cold tolerance in this region. [ABSTRACT FROM AUTHOR]

In this study, various alkali-pretreated lignocellulose enzymatic hydrolyses were evaluated by using three standard pairs of Miscanthus accessions that showed three distinct monolignol (G, S, H) compositions. Mfl26 samples with elevated G-levels exhibited significantly increased hexose yields of up to 1.61-fold compared to paired samples derived from enzymatic hydrolysis, whereas Msa29 samples with high H-levels displayed increased hexose yields of only up to 1.32-fold. In contrast, Mfl30 samples with elevated S-levels showed reduced hexose yields compared to the paired sample of 0.89–0.98 folds at p < 0.01. Notably, only the G-rich biomass samples exhibited complete enzymatic hydrolysis under 4% NaOH pretreatment. Furthermore, the G-rich samples showed more effective extraction of lignin–hemicellulose complexes than the S- and H-rich samples upon NaOH pretreatment, resulting in large removal of lignin inhibitors to yeast fermentation. Therefore, this study proposes an optimal approach for minor genetic lignin modification towards cost-effective biomass process in Miscanthus . [ABSTRACT FROM AUTHOR]

Polyploidization is regularly regarded as an important tool for the generation of innovative germplasm resources and plant breeding. In this study, autopolyploid switchgrass lines were produced from calli derived from immature inflorescence of tetraploid switchgrass ( Panicum virgatum L.), both lowland cv. Alamo and Kanlow, and upland cv. Ranlow, through colchicine treatments. Ploidy levels of plantlets regenerated from the calli were screened by flow cytometry. Growth characteristics of the tetraploid and octoploid switchgrass cultivars were further investigated in a field experiment. Compared with the tetraploid plants of the three switchgrass cultivars, the corresponding octoploid plants showed significant reduction in plant height, number of tillers per plant and fresh matter, but an increase in leaf length and width. [ABSTRACT FROM AUTHOR]