"Exogenous boron alleviates salt stress in cotton by maintaining cell wall structure and ion homeostasis".

Salt stress is considered one of the major abiotic stresses that impair agricultural production, while boron (B) is indispensable for plant cell composition and has also been found to alleviate salt stress. However, the regulatory mechanism of how B improves salt resistance via cell wall modification remains unknown. The present study primarily focused on investigating the mechanisms of B-mediated alleviation of salt stress in terms of osmotic substances, cell wall structure and components and ion homeostasis. The results showed that salt stress hindered plant biomass and root growth in cotton. Moreover, salt stress disrupted the morphology of the root cell wall as evidenced by Transmission Electron Microscope (TEM) analysis. The presence of B effectively alleviated these adverse effects, promoting the accumulation of proline, soluble protein, and soluble sugar, while reducing the content of Na+ and Cl- and augmenting the content of K+ and Ca2+ in the roots. Furthermore, X-ray diffraction (XRD) analysis demonstrated a decline in the crystallinity of roots cellulose. Boron supply also reduced the contents of chelated pectin and alkali-soluble pectin. Fourier-transform infrared spectroscopy (FTIR) analysis further affirmed that exogenous B led to a decline in cellulose accumulation. In conclusion, B offered a promising strategy for mitigating the adverse impact of salt stress and enhancing plant growth by countering osmotic and ionic stresses and modifying root cell wall components. This study may provide invaluable insights into the role of B in ameliorating the effects of salt stress on plants, which could have implications for sustainable agriculture.

Effect of exogenous l-aspartate nano­calcium on root growth, calcium forms and cell wall metabolism of Brassica napus L.

Currently, l-aspartate nano­calcium (Ca(L-asp)-NPs) has been sued as a calcium supplement for humans, but its effects on plants are not well elucidated. This study aimed to investigate the effect of exogenous Ca(L-asp)-NPs on the growth of rapeseed (Brassica napus L.) for the first time. Different concentrations (0, 50, 100, 150, and 200 mg L-1) of Ca(L-asp)-NPs and 1.18 g L-1 Ca(NO3)2 were used in the nutrient solution. The results indicated that Ca2+ released from Ca(L-asp)-NPs were absorbed by the roots, and had a significant effect on plant height, root length, biomass accumulation, and root structure formation, especially on the growth and development of coarse roots at 100 mg L-1 Ca(L-asp)-NPs. Calcium (Ca) accumulation, Ca-pectinate, Ca-phosphate and Ca­carbonate, and Ca-oxalate in plant roots and leaves were positively linked with Ca(L-asp)-NPs concentration. For cell wall, Ca(L-asp)-NPs treatment increased the content of pectin, and the activity of cell wall degrading enzymes in roots, such as pectin methyl-esterase (PME), cellulose enzyme (CE), polygalacturonase (PG), and ß-galactosidase (ß-Gal). For cell membrane osmotic regulation, Ca(L-asp)-NPs promoted the accumulation of soluble sugar and soluble protein. This finding suggests that 100 mg L-1 Ca(L-asp)-NPs had the best growth-promoting effect on rapeseed. This study provides a valuable reference for exogenous Ca(L-asp)-NPs as new nano Ca supplements for plant growth.