Atsushi Kamata

Salt stress is a major constraint to crop productivity, negatively affecting plant physiology and fruit quality. This study hypothesized that seed priming with polyethylene glycol (PEG6000) might enhance antioxidant activity by mitigating oxidative stress in Solanum lycopersicum ‘Micro-Tom’ under salt stress. Seeds primed with –1.2 MPa PEG6000 were grown in Rockwool and treated with 0, 50, 100, 150, and 200 mM NaCl. Primed plants showed a 32% increase in leaf potassium (K⁺) and a 28% decrease in sodium (Na⁺) accumulation compared to non-primed plants under 150 mM NaCl. Glucose, fructose, and sucrose contents increased by 25%, 22%, and 19%, respectively, in primed fruits, while citric acid decreased by 15%. Malondialdehyde (MDA) and electrolyte leakage were reduced by 35% and 29%, respectively, in primed plants under moderate salinity. Antioxidant enzyme activities—SOD, POD, CAT, and APX were enhanced by 30–45% in primed plants under 100 and 150 mM NaCl, compared to non-primed controls. Abscisic acid (ABA) levels increased by 40% in primed roots under salt stress. Activities of polyamine-related enzymes (DAO, PAO, and ADC) also rose significantly. Priming improved protein content by 20% and relative water content by 18%. These results suggest that PEG6000 seed priming enhances salt tolerance by boosting antioxidant defense, regulating osmotic balance, and improving ion homeostasis, offering a viable strategy for sustaining tomato productivity under salinity.

This study investigated the accumulation of nitrate and nitrite, as well as the vitamin C content, in various leafy vegetables, including amaranth greens, katuk, morning glory, squash leaves, vine spinach, leaf lettuce, romaine lettuce, Vietnamese basil, Vietnamese perilla, komatsuna, leeks, and spinach, grown with either organic or synthetic fertilizers. The findings indicate that the type of fertilizer significantly influences nitrate accumulation and vitamin C content in these vegetables. Organic fertilizers were found to reduce nitrate levels and increase vitamin C content in amaranth greens, katuk, morning glory, squash leaves, vine spinach, leaf lettuce, Vietnamese basil, Vietnamese perilla, and spinach compared to the results for synthetic fertilizers. However, high nitrate concentrations in leaf lettuce, komatsuna, and spinach pose potential health risks. The study also identified elevated nitrate levels in vegetables that are not currently regulated. Furthermore, more than half of the samples contained nitrite, for which no maximum permissible level has been established. These findings underscore the importance of organic vegetable cultivation in enhancing both human health and environmental sustainability.

Water scarcity and climate change pose significant challenges to sustainable agriculture, emphasizing the need for optimized irrigation practices. This study evaluates the impact of limited irrigation (0.45 L/day per plant) compared to a control (0.87 L/day per plant) on tomato fruit quality and metabolic responses. Limited irrigation enhanced fruit flavor by reducing the pH from 4.2 to 3.4 and improved cellular integrity, with electrolyte leakage decreasing from 50% to 26%. Antioxidant levels increased, with the vitamin C content rising from 49 to 64 mg 100 g⁻¹ FW, while glucose and fructose accumulation contributed to improved sweetness. Notably, limited irrigation suppressed ethylene biosynthesis, reducing methionine, ACC, ACO activity, and ethylene production, which are key regulators of ripening and senescence. This suppression suggests the potential for extending shelf life and delaying over-ripening. These findings underscore the dual benefits of limited irrigation: enhancing fruit quality and supporting sustainable water use. This research provides a viable strategy for optimizing tomato production and postharvest quality in water-limited regions.

The excess presence of calcium carbonate (CaCO₃) in soil poses challenges for production of horticultural crops, including tomatoes. This condition is prevalent in arid and semi-arid regions of Afghanistan. The objective of this study was to evaluate the effects of elevated concentrations of CaCO₃ on growth, physiology, and quality attributes of tomato. Seedlings were exposed to different concentrations of CaCO₃ (0%, 2.5%, 5%, 10%, and 20% w/w) in soil. The results showed that elevated concentrations of CaCO₃ (10% and 20%) significantly increased soil electrical conductivity (EC) and pH, and subsequently affected growth, physiology, and quality of tomato. CaCO₃ effects resulted in an increase in leaf electrolyte leakage, leaf calcium content, root respiration rate, root ethylene production, fruit firmness, total soluble solids, ascorbic acid, and organic acids, as well as a decrease in plant height, leaf length, leaf magnesium content, leaf SPAD value, number of leaves per plant, root weight and length, and root activity. At higher concentrations, CaCO₃ decreased number of flowers and fruit per plant, as well as fruit weight and diameter, consequently affecting yield production. Although elevated concentrations of CaCO₃ is characteristic of soils in Afghanistan, limited information is available about this topic. These findings enhance our understanding of soil conditions in the country and provide valuable insights for farmers.