This study was designed to investigate the relationship between the caloric value and salt tolerance of two varieties of Miscanthus sacchariflorus (Amur silvergrass: M127 and M022). The salt tolerance capacity, photosynthetic characteristics, Na⁺ and K⁺ uptake by the roots and aboveground parts, and caloric value of different parts of the aboveground parts were obtained under hydroponic conditions. The results showed that M022 was more tolerant to salt stress than M127 and the former had a higher photosynthetic efficiency as well as a lower aboveground Na⁺ accumulation, K⁺ efflux, and larger K⁺/Na⁺ ratio. The calorific values of stems, spear leaves, aging leaves, and functional leaves of the two varieties showed a decreasing trend with increasing NaCl concentration. At 270 mM NaCl, the calorific values of the stems, aging leaves, functional leaves, and spear leaves was reduced by 18.10%, 46.73%, 26.11%, and 18.35% for M022 and 41.99%, 39.41%, 34.82%, and 45.09% for M127 compared to the controls, respectively. We observed that the aging leaves of M022 had a faster decline rate in calorific value than those of M127, indicating that the aging leaves of M022 preferentially isolated the harmful Na⁺ ion, reduced its accumulation in other parts, and increased the K⁺/Na⁺ ratio in the corresponding parts, thus inhibiting the decrease in calorific value. Following this result, it can be inferred that M022 inhibited the decline in calorific values during stress by efficiently compartmentalizing the distribution of Na⁺ and K⁺. Our results provide a theoretical basis and technical support for the efficient cultivation of salt-tolerant energy plants in saline–alkaline soil.

As one of the most salt-tolerant grasses, characterizing salt-tolerance genes of Zoysia matrella [L.] Merr. not only broaden the theoretical information of salt tolerance, but also provide new salt-resistant genetic resources for crop breeding. The salt-inducible protein disulfide isomerase (ZmPDI) of Zoysia matrella [L.] Merr. was proved to enhance salt tolerance in homologous overexpression transgenic plants. In order to evaluate its potential application in crops, we conducted the salt tolerance evaluation in heterologous overexpression transgenic rice (OX-ZmPDI), Wild-type (WT) rice, and LOC_Os11g09280 (OsPDI, homologous gene of ZmPDI in rice) knock-out rice generated by CRISPR-Cas9 system (CR-OsPDI). Our findings revealed that OX-ZmPDI rice was higher and exhibited longer main root length, more proline (Pro) and malondialdehyde (MDA), and higher peroxidase (POD) activity than WT control after salt treatment, while CR-OsPDI resulted in contrary phenotypes. These results indicated that ZmPDI can significantly enhance the salt tolerance in rice, whereas loss-of-function of OsPDI reduces the salt tolerance. To further investigate these differences at the molecular level, we collected roots from OX-ZmPDI transgenic, CR-OsPDI transgenic, and wild-type (WT) plants at 0 and 24 h after salt treatment for RNA-seq and data-independent acquisition (DIA) proteome sequencing. Combined analysis of the transcriptome and proteome revealed that ZmPDI has the potential to enhance the salt tolerance of rice by modulating the expression of laccase-6, zingipain-2, WIP3, FKBP65, AKR4C10, GBSSII, Pho1, and TRXf1. Those results provided new information for the molecular regulation mechanism by which ZmPDI improves salt tolerance, and prove the potential of ZmPDI for application in crop breeding.

Elucidating the response mechanisms of seashore paspalum (Paspalum vaginatum) roots to salt stress is crucial for breeding salt-tolerant varieties. This study aimed to investigate the morphological, physiological, and surface electrochemical responses of seashore paspalum roots to salt stress. The salt-tolerant genotype Sealsle2000 and salt-sensitive genotype 17U-45 were subjected to 300 mM salt stress for 4 and 8 days. Results showed that salt stress exerted a more pronounced inhibitory effect on root growth than on shoot growth, with Sealsle2000 exhibiting less growth inhibition compared to 17U-45. Under salt stress, Sealsle2000 adsorbed more Na⁺ on the root surface and sequestered them within the roots than 17U-45; furthermore, Sealsle2000 was able to maintain higher K⁺/Na⁺ ratios. In terms of physiological mechanisms, Sealsle2000 maintained higher activities of superoxide dismutase and catalase, as well as elevated levels of osmotic adjustment substances (proline and soluble sugars) in roots, which collectively alleviated membrane lipid peroxidation damage and osmotic stress. Compared to 17U-45, Sealsle2000 possessed more negative charges and functional groups on the root surface, which contributed to its higher Na⁺ adsorption capacity and enhanced salt tolerance. Collectively, these findings establish a theoretical framework for understanding the salt tolerance mechanisms of seashore paspalum and other plants.