Soil salinization is a growing concern that degrades soil quality and inhibits agricultural productivity. Miscanthus species have received wide attention because of their high calorific potential, their value as an energy plant, and their ability to maintain high biomass accumulation. However, most studies focused on the biochemical and physiological responses to salt stress while neglecting the osmotic adjustment processes and the contribution of both organic and inorganic substances to these processes. This study evaluates the response mechanism of Miscanthus sinensis to salt stress (0-300 mM of NaCl) by evaluating the growth and photosynthetic parameters, photosynthetic response to light, and contribution of organic and inorganic substances to osmotic potential. The results revealed that M. sinensis adopted Na + compartmentalization and reallocation of biomass to the aboveground parts to mitigate the negative impact of salinity stress. Specifically, Na+ accumulated more in the root and leaf, with an increment magnitude of 75.4-173.9 and 56.7-217.1 times, respectively. This was supported by the changing trend of the stem/leaf ratio (25.1 %-55.9 %) compared to the root/shoot ratio (12.3 %-18.3 %). Also, salt-induced stress decreased the leaf's water content and water use efficiency as a result of low intracellular osmosis, and to mitigate osmotic damage, M. sinensis enhanced the accumulation of proline. These results offer theoretical and scientific insights into managing the cultivation and improving the yield of M. sinensis and other energy herbaceous plants in saline soils.

Miscanthus is a promising perennial lignocellulosic crop for biomass production. To avoid competing with arable land used for food crops to promote carbon neutrality, cultivating Miscanthus on marginal land, especially in saline soils in China, is a recommended strategy. However, the adaptability of Miscanthus species in saline soil remains largely unknown. In this study, a total of 354 genotypes, including Miscanthus sinensis, Miscanthus floridulus, Miscanthus sacchariflorus, Miscanthus lutarioriparius and interspecific species hybrids derived from M. sinensis and M. lutarioriparius, were evaluated under different planting times (May and August), salinity levels (low and moderate) and pest damage assessment by Helicoverpa armigera in the Yellow River Delta (YRD), in China. The significant effects of planting time on the adaptability of Miscanthus were observed. Planting in May in the YRD, Miscanthus had a lower establishment survival rate (28.76%) and overwintering rate (72.31%), but a dry weight higher than that of planting in August. In contrast, planting in August in the YRD had a very high establishment survival rate (91.14%) and overwintering rate (80.65%), which indicated August was the optimal month for planting Miscanthus in the YRD, while May could be suitable for screening salinity tolerance in Miscanthus. In addition, using the overall adaptability score calculated by establishment survival, overwintering ability, key agronomic traits and pest damage assessments to evaluate all genotypes in this study indicated that the adaptability of M. lutarioriparius was superior to other species. However, M. lutarioriparius is more sensitive to pest damage than others. Furthermore, interspecific hybrids in Miscanthus exhibited outstanding biomass production and adaptability in this region, indicating that creating hybrids would be the best breeding strategy for marginal lands. These results provide an important theoretical basis for the development of Miscanthus in saline soil in the YRD, China.

Miscanthus x giganteus is often considered as a suitable plant species for phytomanagement of heavy metal polluted sites. Nevertheless, its physiological behavior in response to the level of metal toxicity throughout the growing season remains poorly documented. Miscanthus x giganteus was cultivated on three sites in Belgium (BSJ: non-polluted control; CAR: slightly contaminated; VM strongly polluted by Cd, Pb, Cu, Zn, Ni and As). The presence of Miscanthus improved soil biological parameters assessed by measurement of enzyme activity and basal soil respiration on the three considered sites, although to a lower level on VM site. Heavy metal accumulation in the shoot was already recorded in spring. It displayed a contrasting distribution in the summer leaves since heavy metals and As metalloid accumulated mainly in the older leaves of CAR plants while showing a uniform distribution among leaves of different ages in VM plants. Comparatively to plants growing on BSJ, net photosynthesis decreased in plants growing on CAR and VM sites. The recorded decrease was mainly related to stomatal factors in CAR plants (decrease in stomatal conductance and in Ci) but to non-stomatal factors such as decrease in carboxylation efficiency and non-photochemical quenching in VM plants. Stomata remained open in VM plants which presented lower instantaneous and intrinsic water use efficiencies than CAR and BSJ plants. High proportions of heavy metals accumulated in CAR plants were bound to the cell wall fraction while the soluble and organelle-rich fractions were proportionally higher in VM plants, leading to a decrease in cell viability and cell membrane damages. It is concluded that not only the intensity but also the nature of physiological responses in Miscanthus x giganteus may drastically differ depending on the pollution level.