View full abstract

We investigated the effects of leaf- and root-pruning treatment of cell seedlings at planting time on plant growth, nitrogen uptake, harvest time, and yield in Japanese bunching onion (Allium fistulosum L.). Leaf-pruning treatment had a negative effect on the number of living leaves and leaf sheath diameter, which were inhibited until harvest on August 20; however, although the number of roots and root growth were temporarily inhibited, the growth was equal to that of the control on July 19. Root-pruning treatment negatively affected the number of emergent leaves, plant height, number of living leaves, shoot weight, leaf sheath diameter, number of roots, and growth of roots until harvest on August 20. The total amount of nitrogen uptake was lower in the root-pruning treatment than that in the leaf-pruning treatment. Plants of all treatments reached the market standards for height on July 19, although the target yield of 300 kg・a⁻¹ was reached from the control on July 19, then from the leaf-pruning treatment on August 5, and from the root-and leaf-pruning treatments on August 20.

View full abstract

We developed a new culture system to facilitate the indoor use of bedding plants. In this system, lightweight organic culture medium is wrapped in a flat cloth container made of a discarded school uniform. In this study, the composition and volume of culture medium appropriate for this culture system were investigated. Marigold and dianthus planted in coir or a mixture of coir and peat moss grew as well as those in the standard mixed red clay soil, while peat moss alone inhibited growth. Plants grown in the cloth container were slightly smaller than those grown in a usual plastic pot, presenting no problem for practical production. The appropriate volume of the medium was 200 mL or more, because a smaller volume such as 100 mL caused growth inhibition. Fungus often grew on the cloth container, which should be controlled to maintain the commercial value. It was classified as the genus Simplicillium on the basis of ITS sequence analysis.

View full abstract

To effectively produce apple with red coloration and marked eating quality, we investigated the efficacy of a chemical defoliant. The manual removal of leaves covering fruit to improve coloration is a labor-intensive process, and a defoliant consisting of fenitrothion is expected to be a substitute for this process. Leaves fell heavily on treatment with the defoliant, with an increase in the average maximum temperature for three days from days one to three after the treatment, and the optimum efficiency of defoliation was obtained when the average maximum temperature for three days was 27°C. The optimal time point to apply the defoliant to ‘Fuji’ was two months before harvest, being one month earlier than the standard time point for Morioka. When leaves covering fruit were removed two months before harvest, the soluble solid concentration of the fruit in trees with a low leaf-fruit ratio was lower than in trees with a high leaf-fruit ratio. The water core of ‘Fuji’ was not reduced by leaf removal at two months before harvest in the case of a high leaf-fruit ratio, whereas it was reduced by leaf removal at one month before harvest in the case of a low leaf-fruit ratio. The fruit eating quality was not influenced by leaf removal at two months before harvest when 60 leaves per fruit were maintained on the trees. Therefore, when leaves are removed by a defoliant two months before harvest, the crop load of the trees should be controlled to maintain 60 leaves per fruit. Since the improvement of fruit coloration raised the price rating, the profit per day was estimated to increase, although the number of fruit on the trees was reduced to maintain a high leaf-fruit ratio. The time required for manual leaf removal was estimated to be reduced by 60% using the defoliant.

View full abstract

In order to improve the uniformity in the flowering period of summer-to-autumn flowering-type chrysanthemums, the influence of a previous history of cuttings on flowering was investigated in Exp. 1 using two cultivars, ‘Minoru’ and ‘Okinamaru’. The flowering period was markedly influenced by individual mother stocks and the node number where the cuttings were taken from. In Exp. 2, paying attention to the difference between mother stocks, the possibility of line selection was examined to improve the uniformity of flowering. In the first year, using three cultivars, ‘Okinamaru’, ‘Hiroshimabeni’, and ‘Kosuzu’, 1-5 lines of each cultivar were chosen as earlier or later flowering lines. In the next year, these selected lines were cultivated under the condition of rain-protected culture. In comparison with the control, the flowering periods became shorter and the coefficient of variance in the flowering became smaller. The earlier or later flowering characters of these selected lines were replicated in the examination under the condition of an open field in another year. In the supplementary test without training, the flowering period of these selected lines became shorter and the ratio of cut flowers which bloomed for the peak seven days increased.

View full abstract

The relationship between Brix values of the butt end of spears and storage roots was examined in semi-forcing green asparagus (Asparagus officinalis L.) cultivation. The Brix values of spring stems peaked at the beginning of harvest and then gradually decreased over the harvest period. The Brix values at 7 to 9 years after planting were significantly higher than those after 3 and 5 years. This difference in Brix values with plant aging was similar to that in the summer-autumn stems. Brix values were also used to estimate sugar concentrations in the roots; the patterns of increase and decrease in Brix values of the butt end of spears were similar to those of storage roots. A strong positive correlation (r = 0.9166, P < 0.01) was found between the Brix values of the butt end of spears and those of storage roots during the harvest period of spring stems. Similarly, a positive correlation (r = 0.6963, P < 0.01) was found for the Brix values of spears and storage roots during the harvest period of summer-autumn stems. These results suggest that the amount of sugar accumulated in roots can be estimated from the Brix values of the butt end of spears.

View full abstract

The effects of high-temperature treatment for enhancing budbreak in ‘Delaware’ grapes grown under forced conditions in Shimane Prefecture were investigated. Cuttings (10 cm) with one bud each were treated with high temperature at 35°C and 40°C in November, December, and January. Treatments for 48 h at 35°C and 24–48 h at 40°C led to a significantly higher budbreak rate than in controls (23°C 12 h-L/18°C 12 hD). Additionally, the number of days required for budbreak (NDRB) increased when treated at 25°C in November and December compared to treatments at 30°C in November and 35°C in December. On the other hand, NDRB for 24 and 48-h treatments in December and January were lower than for 8-h treatments. Treatment at 40°C also resulted in a lower NDRB than that at 35°C, where the NDRB with intermittent treatment (heating for 4 h/d) was higher than that with continuous treatment. The NDRB on treatment at 25°C in November and December was higher than on treatment at 30°C in November or 35°C in December. NDRB with 24-h treatment was also higher than that with 48 and 64-h treatments in November. Lastly, the NDRB was lower if the high-temperature treatment was performed for longer. These results suggest that high-temperature treatments may promote budbreak and may also be dependent on the exposure period and temperature.

View full abstract

Typically, in forcing culture of strawberry (Fragaria × ananassa Duch.), plants raised in a nursery are transplanted to fields immediately after low temperature and dark treatments for the induction of terminal inflorescence. However, often after transplantation, the flowering of the primary axillary inflorescence is delayed due to a high field temperature after transplanting. Here, we analyzed a method for reducing the flowering delay. We noted that the flowering delay could be reduced by maintaining the plants in the nursery for an extended period of three weeks and applying 2 g of isobutylidenediurea fertilizer containing 10% nitrogen to each plant maintained under 50% shade. Our results showed the reduction of flowering delay in non-transplanted plants compared with transplanted ones. This treatment was found to be useful in reducing flowering delay of the primary axillary inflorescence regardless of the climatic conditions after transplanting, and, therefore, could contribute to obtaining stable yields in the forcing culture of the strawberry cultivar ‘Fukuoka S6’.

View full abstract

Typically, asparagus dormancy is induced under 16°C. However, seedlings grown in unheated greenhouses are often subjected to night temperatures lower than 16°C. We investigated whether young asparagus has a developmental phase that prevents it from acquiring the ability to become dormant using three cultivars, Welcome, PA100, and Super Welcome. Sixteen different kinds of aged plant were used in each cultivar. The plants were incubated at 16 or 22°C for 12 days. Spear emergences were observed in plants of all ages of ‘Welcome’ and ‘PA100’ incubated at 22°C, suggesting that these plants were not in the dormant stage. Among the plants incubated at 16°C, spear emergences were observed only in those aged 85 days or less of the cultivars, ‘Welcome’ and ‘Super Welcome’, and in those aged 105 days or less of the cultivar ‘PA100’. These results suggest that young asparagus plants have a developmental phase that prevented them from acquiring the dormancy characteristic. Although most of the 185- and 195-day-old plants were not induced to undergo dormancy at 22°C in ‘Welcome’ and ‘PA100’, approx. 40% of the plants were induced in ‘Super Welcome’. Additionally, almost all of the 185- and 195-day-old plants were induced to undergo dormancy at 16°C in ‘Welcome’ and ‘Super Welcome’, whereas 20–30% of the plants were not induced in ‘PA100’. Thus, we suggest that the temperature for inducing dormancy varies among cultivars.

View full abstract

‘Rainbow Red’ (Actinidia chinensis Planch.) kiwifruit fruits on vines soften gradually. The fruits ripen in a short time after harvest, necessitating a novel long-term storage method. The effects of precooling during or after harvesting on 1-methylcyclopropene (1-MCP) treatment effects were investigated using ‘Rainbow Red’. The effects of 1-MCP treatment varied with the harvesting time, precooling periods, and precooling temperature. In comparison with the control, the 1-MCP treatment fruits harvested in the middle of September did not show differences when harvested 124 days later. Of note, 1-MCP treatment of fruits before precooling below 10°C for 2 days helped to maintain high-level hardness even at four months after the harvest. In addition, fruits stored for 121 days after the harvest ripened after ethylene treatment, although no ethylene was generated. Thus, short-term precooling increases the effects of 1-MCP treatment.

View full abstract

Investigations of the physical properties of fruit before and after cooking and a sensory evaluation after cooking were conducted with 5 eggplant cultivars including ‘Yatakei’, a native strain of ‘Kamonasu’ in Nara. The moisture content and firmness were measured of flesh cubes of 2 × 2 × 2 cm before and after being either steamed or fried with salad oil. The fried flesh was then evaluated with respect to its taste quality and texture related to the oiliness. As the results, the total weight of flesh was increased by steaming and decreased by frying. The moisture content of flesh was highest in ‘Mizunasu’ and lowest in ‘Kurowashi’ before cooking. It was slightly increased in all cultivars and no significant differences among the 5 cultivars was observed after the steaming. In contrast, a marked decrease and a significant difference in the moisture content of flesh were noted in the 5 cultivars by frying. The moisture content of the fried flesh was higher in ‘Yatakei’ and ‘Kurowashi’ whereas they contained lower oil levels than the others. A significant negative relationship between the moisture and oil contents of fried flesh was found. Before cooking, the firmness of flesh was significantly different among the 5 cultivars, being highest in ‘Kurowashi’ and lowest in ‘Mizunasu’, and it was markedly reduced after cooking. It was highest in ‘Yatakei’ and lowest in ‘Senryonigo’ after steaming, but highest in ‘Mizunasu’ and lowest in ‘Senryonigo’ and ‘Shoyaonaga’ after frying. Sensory evaluation revealed a significant difference in the texture related to oiliness among cultivars, with higher levels of oiliness found in ‘Shoyaonaga’ and ‘Mizunasu’ compared to ‘Yatakei’. There was a strong relationship between the texture related to oiliness and the content of moisture or oil in the fried flesh.

View full abstract

The effects of continuous treatment with sugars on the vase life of cut dahlia flowers were investigated. Isothiazolinonic germicide and aluminum sulfate were combined as germicides for sugar treatments. Continuous treatments with glucose at 2.5 or 5% significantly extended the vase life of cut ‘Kokucho’ dahlia flowers and the relative fresh weight was most increased the most by 5%. Treatment with glucose alone, fructose alone, or sucrose alone at 5% or combined treatment with 2.5% sucrose and 2.5% fructose similarly extended the vase life of ‘Kokucho’ dahlia. The combined treatment with sucrose and fructose did not cause petal disorder. Moreover, the combined treatment with sucrose and fructose significantly extended the vase life and increased the relative fresh weight of cut flowers in eight dahlia cultivars.

View full abstract