(1) Background: Previous research has demonstrated that the cation exchange capacity (CEC) of soil and the balance of exchangeable cations Ca, Mg, and K are key factors affecting plant growth and development. We hypothesized that balancing exchangeable cations based on increased CEC would improve plant growth and development. (2) Methods: This study conducted a two-phase experiment to evaluate methods for increasing soil CEC and the effects of increasing CEC and balancing Ca, Mg, and K on plant growth. Therefore, we first conducted a soil culture experiment using organic fertilizer, montmorillonite, and humic acid to investigate fertilizers that can effectively increase CEC in the short term. Then, a tomato seedling pot experiment was conducted using the control (CK) and OMHA fertilizer-treated soils collected from soil culture experiments. The CK and OMHA treatment soils were constructed with balanced exchangeable cations and an unbalanced control, respectively. (3) Results: The soil culture experiments revealed that the combination of organic fertilizer, montmorillonite, and humic acid (OMHA treatment) had the most significant effect on increasing CEC. The CEC of the OMHA treatment increased by 41.07%, reaching 27.10 cmol·kg⁻¹. The tomato pot experiments demonstrated that balancing the exchangeable cations in OMHA soil improved the Mg and K nutrition of tomato seedlings and significantly increased SPAD, leaf nitrogen content, and dry weight, while balancing the exchangeable cations in CK soil improved only the K nutrition of tomato seedlings. (4) Conclusions: Overall, balancing exchangeable cations based on increasing CEC can improve soil nutrient availability and alleviate the competition effects of Ca, Mg, and K cations. Low CEC and imbalanced exchangeable cations can be detrimental to tomato seedling growth.

Silicon(Si) is the only element which can enhance the resistance to multiple stresses. However, the role of silicon in medicinal plants under salt stress is not yet understood. This experiment was conducted to study the effects of silicon addition on the growth, osmotic adjustments, photosynthetic characteristics, chloroplast ultrastructure and Chlorogenic acid (CGA) production of Honeysuckle plant (Lonicera japonica L.) under salt-stressed conditions. Salinity exerted an adverse effect on the plant fresh weight and dry weight, whilst 0.5 g L⁻¹K₂SiO₃·nH₂O addition obviously improved the plant growth. Although Na⁺concentration in plant organs was drastically increased with increasing salinity, higher levels of K⁺/Na⁺ratio was obtained after K₂SiO₃·nH₂O addition. Salinity stress induced the destruction of the chloroplast envelope; however, K₂SiO₃·nH₂O addition counteracted the adverse effect by salinity on the structure of the photosynthetic apparatus. K₂SiO₃·nH₂O addition also enhanced the activities of superoxide dismutase and catalase. To sum up, exogenous Si plays a key role in enhancing its resistance to salt stresses in physiological base, thereby improving the growth and CGA production of Honeysuckle plant.

Salvia miltiorrhiza, which is commonly known as Danshen, is a traditional Chinese herbal medicine. To illustrate its physiological and biochemical responses to salt stress and to evaluate the feasibility of cultivating this plant in saline coastal soils, a factorial experiment under hydroponic conditions was arranged on the basis of a completely randomised design with three replications. Five salinity treatments (0, 25, 50, 75 and 100 mM NaCl) were employed in this experiment. The results showed that salinity treatments of <100 mM NaCl did not affect the growth of Salvia miltiorrhiza in a morphological sense, but significantly inhibit the accumulation of dry matter. Salinity treatments significantly decreased the Chl-b content but caused a negligible change in the Chl-a content, leading to a conspicuous overall decrease in the T-Chl content. The Na⁺ content significantly increased with increasing hydroponic salinity but the K⁺ and Ca²⁺ contents were reversed, indicating that a high level of external Na⁺ resulted in a decrease in both K⁺ and Ca²⁺ concentrations in the organs of Salvia miltiorrhiza. Salt stress significantly decreased the superoxide dismutase (SOD) activity of Salvia miltiorrhiza leaves in comparison with that of the control. On the contrary, the catalase (CAT) activity in the leaves markedly increased with the increasing salinity of the hydroponic solution. Moreover, the soluble sugar and protein contents in Salvia miltiorrhiza leaves dramatically increased with the increasing salinity of the hydroponic solution. These results suggested that antioxidant enzymes and osmolytes are partially involved in the adaptive response to salt stress in Salvia miltiorrhiza, thereby maintaining better plant growth under saline conditions.

In this study, the carbon (i.e., C) bio-sequestration within phytoliths (PhytOC) in 51 rice cultivars was evaluated to breed cultivars with a high efficiency of carbon sequestration in phytoliths and high productivity. The phytolith extraction from rice plants was achieved through wet digestion procedures, and the C content of phytoliths was determined using an Elemental Analyzer 3000. The phytolith contents in the rice organs ranged from 9.69 to 175.52 mg g⁻¹, with significant differences in the phytolith contents in the different organs of each rice cultivar. The estimated PhytOC fluxes of rice plants in 51 rice cultivars were approximately 0.006–0.035 Mg-e-CO₂ per ha per year. High variation coefficients of phytoliths and contents of phytoliths of plant in indica and japonica rice cultivars implied considerable variation among these rice cultivars. Additional results showed no correlation between the phytolith contents and the C content of phytoliths (R = 0.170, p > 0.05), and the C content of phytoliths was significantly correlated with the PhytOC content in dry plant weight (R = 0.804, p < 0.01). However, the estimated PhytOC flux was significantly correlated with the phytolith content (R = 0.651, p < 0.01), with the C content of phytoliths (R = 0.512, p < 0.01) and with the PhytOC content in dry plant weight (R = 0.727, p < 0.01). Selected rice cultivars herein with a high efficiency of C sequestration in phytoliths and high productivity, therefore, played important roles in controlling the C sink and Si biogeochemical cycle in soil-rice systems.