High salinity land may provide an alternative resource for the cultivation of dedicated biomass crops for renewable energy and chemicals, thus avoiding competition for land use with food crops. The commercial perennial grass Miscanthus 9 giganteus is a leading biomass crop; however, its response to salt stress is largely unknown. Miscanthus 9 giganteus was grown in pots irrigated with nine different NaCl concentrations (0, 2.86, 5.44, 7.96, 10.65, 14.68, 17.5, 19.97 and 22.4 dS m À1 ). Biomass yield was reduced by 50% at 10.65 dS m À1 NaCl. Root dry matter inhibition occurred at the highest salt concentration tested, while rhizome dry weight and the ratios of root/rhizome and below-/above-ground dry matter were not affected by elevated salinity. The accumulative effect of increasing salinity reduced stem height and elongation, while photosynthesis was reduced to a smaller extent. The duration and strength of salinity exacerbated the reduction. Water use efficiency (WUE) was maintained except at the highest salinity and plants maintained stomatal conductance (g s ) and leaf water content at low to moderate salinity. Miscanthus 9 giganteus showed strong induction of the osmoprotectant, proline and no significant increase in malondialdehyde content under increasing salinity. The ash content in leaves, increased, reducing the biomass quality at high salinity concentrations. The effects of salinity on the yield and the availability of land area in European geographical area for agriculture were investigated. Understanding the potential for growth of the C4 biomass crop Miscanthus on underutilized or abandoned land may offer a new range of targets for improved economics, crop management and breeding.
Background and AimsWater deficit and salinity stresses are often experienced by plants concurrently; however, knowledge is limited about the effects of combined salinity and water deficit stress in plants, and especially in C4 bioenergy crops. Here we aim to understand how diverse drought tolerance traits may deliver tolerance to combinations of drought and salinity in C4 crops, and identify key traits that influence the productivity and biomass composition of novel Miscanthus genotypes under such conditions.MethodsNovel genotypes used included M. sinensis and M. floridulus species, pre-screened for different drought responses, plus the commercial accession Miscanthus × giganteus (M×g.). Plants were grown under control treatments, single stress or combinations of water deficit and moderate salinity stress. Morphophysiological responses, including growth, yield, gas exchange and leaf water relations and contents of proline, soluble sugars, ash and lignin were tested for significant genotypic and treatment effects.Key ResultsThe results indicated that plants subjected to combined stresses showed more severe responses compared with single stresses. All novel drought-tolerant genotypes and M×g. were tolerant to moderate salinity stress. Biomass production in M. sinensis genotypes was more resilient to co-occurring stresses than that in M×g. and M. floridulus, which, despite the yield penalty produced more biomass overall. A stay-green M. sinensis genotype adopted a conservative growth strategy with few significant treatment effects. Proline biosynthesis was species-specific and was triggered by salinity and co-occurring stress treatments, mainly in M. floridulus. The ash content was compartmentalized differently in leaves and stems in the novel genotypes, indicating different mechanisms of ion accumulation.ConclusionsThis study highlights the potential to select novel drought-tolerant Miscanthus genotypes that are resilient to combinations of stress and is expected to contribute to a deeper fundamental knowledge of different mechanistic responses identified for further exploitation in developing resilient Miscanthus crops.
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