Development prediction models using meteorological data were created to examine the growth characteristics of the tetraploid seedless grape ‘Azumashizuku’. It showed that the effective accumulated temperature method, number of days transformed to the standard temperature method and the nonparametric DVR method using the daily mean air temperature can be used to predict the period of time between the budburst day and day coloration started with practical accuracy. It also indicated that the chilling requirement to break endodormancy of budburst in ‘Azumashizuku’ is less than that of ‘Kyoho’. To accurately predict the beginning of anthesis, the sprouting time should be used rather than the foliation time. Regarding the effective accumulated temperature method, developmental zero temperature showed higher predictive accuracy at 0°C by anthesis and at 5°C from full blossom period to the beginning of the coloration start period.

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Development prediction models using meteorological data were created to examine the maturation characteristics of the tetraploid seedless grape ‘Azumashizuku’. °Brix at the full harvest time was estimated using a multiple regression equation with high-level significance. The predictors of the multiple regression equation were the accumulated actual sunlight duration in the maturation stage and yield. A significant correlation was found between the tartaric acid content at full harvest and the average temperature 3 to 17 days after the start of coloring. The day the sugar/acid ratio would reach 35 was predicted by the nonparametric DVR method using solar radiation; the predictive accuracy is high. It showed that solar radiation had an important impact on the maturation of ‘Azumashizuku’ after the beginning of coloration.

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Spathiphyllum wallisii Regel, which has the beautiful contrast of deep green leaves and a white spathe, is evaluated highly as an indoor ornamental plant. In order to breed new and valuable varieties of Spathiphyllum, crossing with wild species is effective. The breeding of tetraploids is useful for the development of fertile progeny by interspecies or intergeneric crossing. In this study, to establish effective breeding methods for tetraploids, the effects of the in vitro treatments of removing a suitable number of unexpanded leaves before sterilization, leaving a suitable number of leaf primodia remaining with the apical meristem, and the conditions of colchicine treatment were investigated in S. wallisii Regel ‘New merry’. The preparative methods, leaving four or five unexpanded leaves before sterilization and cutting off apical meristematic tissues with three or four-leaf primodia, decreased the contamination rate and sterilization damage of explants. The rate of apical meristems identified as polyploid was increased to 31.3% on fourteen-day colchicine treatment on MS medium, after growing on MS medium containing both NAA at 0.1 µM and BAP at 10 µM for one month. The leaves of the resulting tetraploids showed a broad-shaped form compared to the diploids, and spathes of tetraploids were slightly smaller than those of diploids.

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To avoid replanting problems with asparagus (Asparagus officinalis L.), we demonstrated on-site soil treatment consisting of solar heat disinfection and repeated flood irrigation in three local long-term asparagus fields in Saga Prefecture. Growth of asparagus in soils collected from fields after treatment showed significant increases in the plant height and fresh weight of the below-ground biomass compared to those in soils collected from the field before treatment. This indicates the effective implementation of soil treatment. In fact, the allelopathic activity of soil, examined by in-vitro extension of the radicle of lettuce (Lactuca sativa L.), was significantly reduced by treatment. In addition, the population density of Fusarium oxysporum in soil, known as an important pathogen of asparagus, was below the detection limit on treatment. The soil pH, EC, available phosphate, and nitrate concentration showed significant changes on treatment, whereas exchangeable cations (Ca²⁺, Mg²⁺, and K⁺), base saturation, and the ammonium concentration in soil did not. These results indicate that the high allelopathic activity and population density of pathogens in soil may be important growth-retarding factors for asparagus before replanting. Therefore, the proposed treatment may be an effective method to avoid replanting problems with asparagus.

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We investigated the effects of topsoil dressing, activated carbon, and activated carbon flow on the mitigation of replant failure of Japanese pear (Pyrus pyrifolia (Burm.f.) Nakai) by growing young trees of ‘Kosui’ for two years. Shoot growth was greater in trees planted in a field treated with topsoil dressing than in trees in a non-treated field (control) both at one and two years. The mean weight of trees in the topsoil-dressing field was 170% greater than that of the control at two years. There was no significant difference in growth between trees in an activated carbon or activated carbon flow field and the control. We also compared shoot growth between the trees in a field treated with topsoil dressing along with polyethylene film mulching and those in a field treated with topsoil dressing alone. Both at one and two years, shoot growth was greater in trees in the field treated with topsoil dressing and mulching than in the trees in the field treated with topsoil dressing alone. In conclusion, topsoil dressing has a positive effect on the mitigation of replant failure in young trees. The combination with mulching further promoted the growth of young trees.

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Blotching on the fruit surface, occurring due to the appearance of vascular bundles on the surface with low-level firmness, is an unfavorable character of tomato. The effect of the day temperature on the appearance of blotching on the fruit surface was investigated in this study. When tomato plants were cultivated in a phytotron with day temperatures of 20, 24, and 28°C under the same night temperature of 8°C, the degree of fruit blotching was severe under a day temperature of 20°C. The values of the blotching intensity decreased as the day temperature increased from 20 to 28°C. To apply the results to actual tomato production, tomato plants were grown in a greenhouse. An increase of the minimum day temperature from 8°C to 20°C with a heater led to a significant decrease of the appearance of blotching on the tomato fruit surface, and resulted in a thick fruit skin and high-level firmness.

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Unexpected interruption of night-break-lighting (NB) causes serious deterioration of the quality of cut chrysanthemum flowers. The effects of the timing and duration of NB interruption on flower bud formation were investigated using autumn and summer-autumn flowering chrysanthemum genotypes in Japan. In the autumn flowering genotype of ‘Arajin 2’ flowering in December, more than three and four days of interruption of NB influenced flower bud formation when the interruption occurred 22 and 36 days after planting, respectively. On the other hand, no influence was observed of one to five days of interruption in those flowering in March. In the summer-autumn genotype of ‘Iwanohakusen’, flower bud formation was influenced by more than four days of interruption in July flowering, three days of interruption in August flowering, and more than two days of interruption in September flowering. To reveal genotype differences in the effects of the duration of NB interruption and the plant growth stages subjected to the interruption, three autumn flowering genotypes and two summer-autumn flowering genotypes were compared. Sensitivity to the NB interruption was genotype-dependent: the sensitive genotype showed a reduced leaf number flowering only a day of interruption, but the insensitive genotype showed no effect of three days of interruption. The sensitivity increased with plant growth. The present study demonstrated that the effect of NB interruption was changed by environmental factors such as the temperature, growing stage and juvenility of plants, and the cropping type.

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The effects of gibberellin (GA) and benzylaminopurine (BAP) treatment on endodormancy breaking of bulbils and transplant growth were investigated in Elatostema involucratum Franch. & Sav. The final emergence rates of dormant bulbils dipped in 0, 100, and 500 ppm of GA solution were 0, 84, and 34%, respectively. When the bulbils were treated with a combined solution of GA at 0, 10, 50, or 100 ppm and BAP at 0, 1, or 10 ppm, better emergence rates were observed than when treated with a concentration of 100 ppm of GA. BAP treatment had no effect on endodormancy breaking. However, combination treatment with BAP and GA at a concentration of 10 or 50 ppm led to early germination of bulbils and decreased Desukumi (phenomenon whereby growth of the bud stops after emergence) rates compared to single treatment with a concentration of 10 or 50 ppm of GA. The transplants were treated twice with solution with a concentration of 25 and 100 ppm of GA or BAP in by spraying. The main stem length of transplants treated with GA was significantly longer than that of the control, caused by internode elongation. The number of lateral shoots from the main stem with BAP treatment was significantly higher than that of the control.

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The effect of far-red light (EOD-FR) and heating (EOD-heating) treatment at the end of the day (EOD) on growth for spring shipping of Eustoma grandiflorum (Raf.) Shinn was investigated. Plants treated with both EOD-FR and EOD-heating after transplanting on October 29 showed early flower budding associated with a longer main stem and a higher node number compared with untreated plants. SPAD values of the upper leaves and the nitrogen content of leaves in these plants on May 13 were higher than in other treated plants. In contrast, the nitrogen content of roots in both treated plants was lower than in other plants. On measuring the translocation of photosynthate in the early stages, ¹³C atom% excess in the stems and leaves of plants under 18°C・FR treatment and in roots on EOD-heating was significantly higher than in plants under 18°C treatment. From these results, it was clarified that both treatments of EOD-FR and EOD-heating at 13°C can advance the growth of plants and stems more than 18°C treatment and effect the activation of photosynthate allocation in early developmental stages to promote growth for spring shipping in regions with low leaves of sunshine during winter.

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The effects of the planting season and root mass on shoot growth of one-year ‘Fuji/Marubakaido’ trees were examined after a heading cut was performed of their trunks. Shoot lengths of the trees planted and grafted two springs prior to the measurements (Test Group 1) were higher than those planted the previous fall (Test Group 2) and those planted during the previous spring (Test Group 3). The shoot lengths of trees in Test Group 1 decreased gradually from top to bottom, while in those of Test Groups 2 and 3, the top three-to-four shoots were markedly longer than the shoots below. When half of the roots of Test Group 1 trees were removed prior to the heading cut of the trunk, the shoot length of the top two shoots was markedly longer than that of the shoots below. These suggest that the root condition and root volume may affect the supply of stored nutrients to the shoot, which influences shoot growth, and also has regulatory effect on apical control of shoot growth.

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The delay and inferiority of Japanese persimmon ‘Fuyu’ coloration have become very problematic years. To identify solutions to this problem, this study investigated the effects of treatment with fertilizer containing a natural type of abscisic acid (S-ABA) on fruit skin coloration. Treatment with fertilizer containing S-ABA led to a significant increase in coloration of the fruit apex, reaching a 1.0 higher color chart value, and necessitating a 7–10 day earlier harvesting time compared to controls. Significant effects on treatment with fertilizer containing S-ABA were observed before coloring onset in this study, which corresponds to the period from September to the beginning of October. However, treatment after the onset of coloring was ineffective. Coloration improvement was observed approximately 10 days after the treatment. Significant differences were found in color chart values compared to control fruits until harvesting. These results suggest that coloration improvement on using fertilizer containing S-ABA was due to accelerating the transition to the coloring period.

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Quantitative evaluation of the crisp texture of ‘Taishuu’ persimmon was studied with an acoustic measurement of crispness (AMC). It was found that the crisp texture can be quantitatively evaluated with a higher accuracy using the energy texture index (ETI) calculated from frequency bands from 6,400 to 25,600 Hz. Polyethylene packaging maintained the crisp texture for about 11 to 15 days after harvest. The crisp texture was maintained by the packaging for about 2 to 6 days longer than in fruit without the packaging; i.e., the crisp texture was maintained for about 9 days after harvest. Polyethylene packaging following 1-MCP treatment for 24 h maintained the crisp texture for about 25 days after harvest; i.e., the crisp texture was maintained for about 10 to 14 days longer than in fruit with polyethylene packaging only. The fact that the skin color (color score) increased normally to around 4.2 even after the crisp texture was maintained for 25 days after harvest suggests the practical utility of polyethylene packaging with 1-MCP treatment.

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