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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]

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]

As an important bioenergy crop, switchgrass (Panicum virgatum L.) can produce high biomass yield. However, its biomass yield could be further increased by using beneficial microbe inoculation methods. In this study, a plant beneficial symbiotic microbe strain 11F was isolated and identified as Streptomyces alfalfae , which can produce IAA and siderophore. It is also known to have phosphate-solubilizing and N 2 fixing abilities. In addition, the promoting effects of strain 11F on seed germination and plant growth were evaluated. The results indicated that seeds treated with 11F showed higher germination rates, which observed an increase of 21.9%. Compared with the control, the switchgrass plants treated with strain 11F were found to have longer leaf lengths; greater plant heights, shoot fresh weights and root fresh weights; longer overall total lengths; and larger total plant root surface areas, which were significantly increased, by 30.7%, 25.8%, 49.5%, 42.9%, 39.3%, and 44.8%, respectively. Moreover, an egfp -tagged 11F strain was constructed and the mycelium of the 11F strain was observed on the surfaces of the switchgrass root hairs. The colonization dynamics of the egfp -tagged 11F strain to the rhizosphere soil of the switchgrass showed that it remained stable up to 30 days at 2.65 × 105 CFU g−1 dry weight from the initial inoculums. All of the aforementioned observational results suggest the potential of the S. alfalfae 11F strain in improving establishment and biomass yield of switchgrass. • The strain 11F was isolated and identified as Streptomyces alfalfa based on 16S rRNA and the genomic collinearity. • The S. alfalfa 11F strain can produce IAA and siderophore and have phosphate-solubilizing and N 2 fixing abilities. • The S. alfalfa 11F strain inoculations can effectively promote the seed germination and growth of switchgrass. • The colonization of S. alfalfa 11F strain in the switchgrass rhizosphere was investigated using an egfp -tagged one. [ABSTRACT FROM AUTHOR]

Abstract: Crop productivity is greatly affected by soil salinity, so improvement in salinity tolerance of crops is a major objective of many studies. We overexpressed the Arabidopsis thaliana SOS1 gene, which encodes a plasma membrane Na+/H+ antiporter, in tobacco (Nicotiana tabacum cv. Xanthi-nc). Compared with nontransgenic plants, seeds from transgenic tobacco had better germination under 120mM (mmolL−1) NaCl stress; chlorophyll loss in the transgenic seedlings treated with 360mM NaCl was less; transgenic tobacco showed superior growth after irrigation with NaCl solutions; and transgenic seedlings with 150mM NaCl stress accumulated less Na+ and more K+. In addition, roots of SOS1-overexpressing seedlings lost less K+ instantaneously in response to 50mM NaCl than control plants. These results showed that the A. thaliana SOS1 gene potentially can improve the salt tolerance of other plant species. [Copyright &y& Elsevier]

Abstract: Drought is a major environmental stress factor that affects growth and development of plants. Abscisic acid (ABA), osmotically active compounds, and synthesis of specific proteins, such as proteins that scavenge oxygen radicals, are crucial for plants to adapt to water deficit. LOS5/ABA3 (LOS5) encodes molybdenum-cofactor sulfurase, which is a key regulator of ABA biosynthesis. We overexpressed LOS5 in tobacco using Agrobacterium-mediated transformation. Detached leaves of LOS5-overexpressing seedlings showed lower transpirational water loss than that of nontransgenic seedlings in the same period under normal conditions. When subjected to water-deficit stress, transgenic plants showed less wilting, maintained higher water content and better cellular membrane integrity, accumulated higher quantities of ABA and proline, and exhibited higher activities of antioxidant enzymes, i.e., superoxide dismutase, catalase, peroxidase and ascorbate peroxidase, as compared with control plants. Furthermore, LOS5-overexpressing plants treated with 30% polyethylene glycol showed similar performance in cellular membrane protection, ABA and proline accumulation, and activities of catalase and peroxidase to those under drought stress. Thus, overexpression of LOS5 in transgenic tobacco can enhance drought tolerance. [Copyright &y& Elsevier]

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]