To determine the optimal salinity of irrigation water for fruit radish cultivated in peat, five levels of salinized water were used to evaluate their effect on the growth and quality of fruit radish (Raphanus sativus L.). Results showed that with an increase in salinity, the leaf growth was somehow inhibited, but the fleshy root growth increased, and quality improved with more soluble solids, sugar, protein, and Vitamin C substances in fleshy roots. With an increase in water salinity up to 4.2 dS/m, the weight of fleshy roots increased by 51.10% with a high increment in the root/shoot ratio. With the same salt concentration, the content of soluble solids in both root peal and pulp was the highest and improved by 11.06% and 6.70%, respectively. The soluble sugar content was the highest in root peals with the 4.2 dS/m treatment and in fleshy roots with the 7.4 dS/m treatment, with a 55.85% and 32.30% increase, respectively. The content of both soluble protein and vitamin C with the 4.2 dS/m treatment increased by 11.99% and 113.36%, respectively. Strong evidence derived from the study has indicated that 4.2 dS/m salinized irrigation water is optimal for growing ‘ice-cream’ fruit radishes and maintaining ultimate root weight and quality.

Light quality is an important variable affecting plant growth, so we aimed to explore the impact of light quality on plants under salt stress. The salt tolerance of pea (Pisum sativum L.) seedlings illuminated by LED red light and 4:1 of red/blue light in a hydroponic system was evaluated at three salinity levels (0, 50, and 100 mmol/L of NaCl) for their morphological and physiological parameters and their root growth characteristics in response to salt stress. Results demonstrated that, as salt stress intensified, the plant height, aboveground fresh/dry mass, root growth indices, and chlorophyll content of pea seedlings exhibited a decreasing trend, while the malondialdehyde (MDA) content and the activity of superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT) in leaves increased. Also, more sodium (Na⁺) but less potassium (K⁺) ions were detected due to the change in electrolyte balance. Compared with pea seedlings under no salt stress, the growth rate, plant height, and K⁺ ion content significantly increased with the red light treatments, but both lights did not affect the aboveground fresh/dry mass, chlorophyll content, or root growth index. Under medium salt stress (50 mmol/L), red light helped generate more chlorophylls by 17.06%, accelerate leaf electrolyte exudation by 23.84%, accumulate more K⁺ ions by 46.32%, and increase the K⁺/Na⁺ ratio by 45.45%. When pea seedlings were stressed by 100 mmol/L salinity stress, red light was able to maintain the leaf chlorophyll level by 114.66%, POD enzyme activity by 157.78%, MDA amount by 14.16%, leaf and stem electrolyte leakage rate by 38.76% and 21.80%, respectively, K⁺ ion content by 45.47%, and K⁺/Na⁺ ratio by 69.70%. In conclusion, the use of red light has proven to enhance the salt tolerance of pea seedlings in a hydroponic system, which can and should be a promising approach to prime pea seedlings for more salt tolerance.

The global shortage of freshwater, especially in agriculture, has become a serious threat to food security and safety; therefore, using brackish water with soil amendments in facility-grown vegetable production has drawn more attention recently. In this study, the effects of the combined use of peat or biochar at different rates (1%, 3%, and 5%) on soil properties, plant growth, and physiological responses were investigated in cherry belle radish (Raphanus sativus L.) irrigated with brackish water (5 g/L). The results revealed that peat significantly cut soil electrical conductivity (EC) by 42.61% and the pH value by 0.29, while biochar reduced soil EC by 32.44% but increased the pH value slightly. Both peat and biochar significantly increased the chlorophyll content and photosynthetic characteristics in cherry belle radish leaves and effectively promoted the accumulation of plant biomass. The net photosynthetic rate (Pn) of cherry belle radish in the soil amended with 5% peat or with 3% biochar increased by 89.06% and 85.94%, respectively, compared with CK, while the fresh weight of fleshy roots rose by 74.40% and 50.27%, respectively. This study further found that peat and biochar had effectively inhibited lipid peroxidation and proline accumulation in plants. The plasma membrane permeability was reduced by 41.18% and 39.90%, and the malondialdehyde (MDA) content decreased by 49.66% and 41.90%, respectively. In addition, peat and biochar significantly improved ion homeostasis in plants by increasing the ratios of K⁺/Na⁺ and Ca²⁺/Na⁺ in leaves, with the increment amplitudes reaching 90.21%/81.45% and 60.47%/79.15%, respectively. Nevertheless, biochar exhibited a superior effect compared to peat on balancing plant ions. In conclusion, a proper application of peat or biochar under brackish water irrigation has a significant potential to ameliorate soil properties and alleviate salt stress in plants, providing a safe approach for using brackish water with soil amendments in facility vegetable production in arid and semi-arid regions.