The effects of solar radiation and presence or absence of fruit on transpiration and the moisture retained by the growing plant itself were investigated at the individual level using pot-grown cucumber plants. Plants with 5 to 12 fruits were used to assess transpiration over time by measuring the pot weight on an electronic scale for 3 days. Fruits were removed on the second day of the study to determine whether the presence of fruits caused differences in transpiration and water content in the same plants. Most of the water retained by the plants was in the fruits, and about half of the water absorbed during the night was accumulated in the fruits. The variation in water uptake of cucumber plants with fruit enlargement was greater at night than during the day. Transpiration tended to be higher in the presence of fruit when solar radiation was high. The average solar radiation and transpiration per leaf area could be regressed by a quadratic equation, and the coefficient of the square of the solar radiation term was negative.

We sowed onion (Allium cepa L.) in the same field in fall or spring of the same year and investigated differences in growth at bulb formation and harvest, as well as factors affecting bulb weight. Compared with fall-sown onions, bulb initiation in spring-sown onions was delayed by 1 month while harvest was delayed by 18 days; bulb weights were also lower for spring-sown than fall-sown onions. These results suggest that bulb initiation is related to achievement of the four-leaf stage and subsequent effective cumulative temperature. Leaf bud differentiation was related to cumulative temperature above a base temperature of 5°C. The final number of differentiated leaf buds was constant and did not depend on the sowing time. Given that lodging occurs 2 weeks after the cessation of leaf bud differentiation, which depends on the cumulative temperature, the approximately 20-day delay in harvesting time of spring-sown compared with fall-sown onions is considered to reflect slower accumulation of temperature. Although the timing of flag leaf bud differentiation was affected by the sowing time and degree of development, given that flag leaves emerged in late May regardless of the sowing time, the lower bulb weight of spring-sown onions is attributed to lower numbers of emerged leaves and bulb scales. These results indicate that increasing the total number of emerged leaves and number of bulb scales is important for improving the bulb weight of spring-sown onions.

In this study, the effects of ridge height, planting depth, and presprouting soil mounding on the growth and yield of asparagus were examined using the whole harvest cultivation method for one-year-old plants. The results showed that the planting depth and soil mounding affected the yield parameters of asparagus, such as the mean spear weight and total spear number. The planting depth or soil mounding was effective in increasing the number of thick spears, and factors affecting the mean spear weight differed depending on the planting depth and soil mounding. Soil mounding in shallow plantings increased the mean spear weight and marketable yield rate, resulting in higher yield values compared with no soil mounding. This indicates that soil mounding in presprouting ridges can be used to control the mean spear weight and total spear number.

Lutein is an antioxidant with potential health benefits and is accumulated in spinach. However, little is known about the factors causing variations in the lutein content in spinach for processing. Thus, the effects of seasonal/cultivar variations, seedling thinning, and environmental conditions on lutein contents were investigated. The lutein content rose with increasing cultivation days, despite cultivation seasons. However, the lutein content interacted between cultivation days and cultivars in winter cultivation. A lower leaf water content under low temperatures may also enhance the lutein content. In addition, although plant growth, such as leaf/plant weight, was two-fold higher in thinning than in non-thinning plants, the lutein content was not affected by thinning. Furthermore, positive and negative interactions between environmental conditions and lutein contents were observed. The regression models between the lutein content and plant height/weight could be divided into two linear regressions according to plant development, such as whether the plant had started to bolt at harvest. Therefore, these results suggest the involvement of a decrease in the lutein content by flower bud differentiation/development. We conclude that the lutein content in spinach for processing is affected by cultivars, environmental conditions, and the developmental stage of the plant, such as flower bud differentiation.

Gerbera is one of the important floricultural plants in Japan, and year-round production has been established with soilless culture. Here we investigated the effects of night lighting with red and far-red light emitting diodes (LEDs) on the growth and flower quality of cut gerberas. In the one-year-old gerbera ‘Sandy’, the combinations of end-of-day and night break lightings with either red or far-red LEDs significantly increased the scape length and cut flower weight. In addition, all-night lighting with red LEDs also increased them. However, night lighting with far-red significantly reduced SPAD values in leaves. Of the three night-time periods (end-of-day, night break, and end-of-night), night break was the most effective for elongation of the scape length. In addition, night lighting with red LEDs in a long-photoperiod and high-temperature season (from June to August) might decrease the scape length of cut flowers in October. Taken together, night break lighting for around 4 hours with red LEDs might improve the cut flower quality of gerbera.

In this study, we investigated the response to low temperature and effect of 1-MCP treatment on maintaining fruit quality during postharvest storage in Japanese apricot (Prunus mume Sieb. et Zucc.) fruit of Taiwanese and Japanese cultivars. In all cultivars, fruit softening was repressed at 2, 5, and 8°C compared with 15°C, and the effect was enhanced at lower temperatures. Among the cultivars, ‘Hakuo’ and the Taiwanese cultivar, ‘Taiwan’, which showed no and a very low incidence of chilling injury (CI), respectively, could be stored for a long time at 2°C. On the other hand, ‘Gojiro’ showed frequent CI at 2, 5, and 8°C, and so these temperature conditions were considered unsuitable for long-term storage. As the other 5 cultivars (‘Nanko’, ‘Ellching’, ‘ST’, ‘Hakufunbai’, and ‘85486’) showed frequent CI when stored at 2°C, storage at 5 or 8°C was considered favorable for these cultivars. In addition, ripening-inhibitory effects of 1-MCP treatment were observed as repressed fruit softening, peel color change, and ethylene production in both the Taiwanese cultivar ‘Ellching’ and Japanese cultivar ‘Nanko’. 1-MCP was effective in ‘Ellching’ for suppressing peel color change at 15 and 20°C, and fruit softening at 15°C. On the other hand, 1-MCP treatment at lower storage temperatures such as 0 and 5°C induced CI and adversely affected the maintenance of fruit quality in both cultivars. These results collectively suggest that the late-maturing Taiwanese cultivars have the same or higher resistance to low temperatures compared with Japanese cultivars, and 1-MCP treatment at a certain temperature range is promising for maintaining fruit quality during postharvest storage of Japanese apricot.