In order to develop an efficient procedure for chromosome doubling of lavandin, leaf-derived calli were treated with colchicine. Relatively high adventitious shoot formation rates, from 71.8 to 79.3%, were obtained in the medium with 0.05, 0.1 and 0.5% of colchicine, although almost all shoots showed hyperhydricity. However, root formation rates were seriously decreased. Conclusively, 2, 16 and 7 chromosome-doubled plants were obtained from calli treated with 0.05, 0.1 and 0.5% of colchicine, where the regeneration rates were 0.6, 4.3 and 2.0%, respectively. The leaf lengths of chromosome-doubled plants varied widely, and the stomatal size was significantly larger than that of the original. However, both the floral stalks and spikes of chromosome-doubled plants showed dwarfism. Additionally, the essential oil contents in the floral spikes of chromosome-doubled plants significantly decreased. When the crossability is recognized between chromosome-doubled plants and true lavender, these amphidiploids might be interesting materials for improving horticultural traits of lavender.

View full abstract

Chromosome doubling with colchicine treatment of seedlings derived from cross among hexaploid persimmons (Diospyros kaki Thunb.) were carried out to induce dodecaploid persimmons. Colchicine treatment of the meristem of seedlings in vitro was effective at a concentration of 0.03–0.05% for 12–24 hours. Induced dodecaploid seedlings generally showed weak vigor, but some vigorous seedlings could be obtained. Compared with the hexaploid parent cultivar, these dodecaploid seedlings had longer stomatal guard cells and lower stomatal densities. Although the rate of flower bud on dodecaploid seedlings was lower than that of the hexaploid seedling, some of the seedlings bore both pistillate and staminate flowers. Since the pollen of the induced dodecaploid seedlings has germination ability, the seedlings could be parental stocks for the breeding of seedless-PCNA persimmons.

View full abstract

We have developed a new growing technique called ‘The Paper Lite cultivation method’ and have now confirmed its efficacy for cultivating Cypripedium macranthos var. speciosum. We used Paper Lite medium (PL medium), which is made from a mixture of rolled paper and vermiculite and placed an aseptic air ventilation filter on the top of the growth container. We transplanted young cultured plants on to the PL medium. Immediately after transplantation, we cultured the plants in a dark place keeping the temperature at 4°C for 120 days. Then the plants were moved to a bright places keeping the temperature at 20°C. We maintained the plants under these conditions for 150 days, and fed them with a special solution prescribed and patented by T. Oyamada every four weeks. Just prior to their acclimatization and potting, plants produced by our method were compared with others produced by the standard methods. The former surpassed the latter in total weight, height and number of leaves, number of roots, and number and development of dormant buds. A year after being potted and moved outdoors, plants grown by our method continued to surpass those grown conventionally in height and number of leaves. The plants were maintained outdoors in pots for one year. We then transplanted them to wild forests. A year after this transplantation, their survival rate was 84%, and the flowering rate was 5%.

View full abstract

This study investigated the effects of storage temperature and gibberellin pretreatment on the germination rate of Swertia japonica seed. When the seeds were stored at less than 5°C, the same germination rate and germination period as those of fresh seeds could be maintained for more than half a year. The germination percentage was not improved when the seeds were soaked in 200 ppm gibberellin for 24 hours prior to seeding. However, soaking in 600 ppm gibberellin for 24 hours inhibited germination. In conclusion, the quality of Swertia japonica seeds could be maintained significantly longer by refrigerating or freezing rather than storage at room temperature. However, we could not clarify the effect of GA on germination of the seeds.

View full abstract

Effects of the amount of irrigation water and its frequency on the yield and growth of tomato (Lycopercicon esculentum Mill) plants under drip fertigation were examined. Treatments consisted of three levels of dripping water quantities (50, 250 and 1,250 mL) combined with two levels of the amount of nutrient application (standard, half dose of the standard). In the 50 mL-irrigated treatment, where plants were irrigated more frequently than in other treatments, more frequent irrigation with reduced amounts of water was most effective for growth and yield of tomato regardless of the nutrient level. Under this treatment, a region with a higher moisture content was formed near soil surface and NO₃⁻ concentration in the petiole sap was enhanced. Such factors may have led to stimulation of water uptake and efficient supply of nutrients.

View full abstract

We cultured cyclamen (Cyclamen persicum Mill.) using cedar bark as a potting medium. The cedar bark comprised 12% solid phase, 55% liquid phase, and 32% gaseous phase; with a bulk density of 0.15 g·mL⁻¹ and pH 6.13. Application of nonionic surfactant (AquaGro 2000L) increased hydrophilia of cedar bark. With trickle irrigation, amendment with surfactant had no effect on the growth and flowering of cyclamen (medium-flowered cultivar ‘F₁ K Middy Chorus’) grown in 15-cm pots. However, with flood and drain irrigation, amendment with surfactant controlled the rise of moisture tension and water repellency of cedar bark, which prevented wilting and improved plant growth. Soaking cedar bark with 0.3% FeSO₄·7H₂O markedly improved growth and flowering of cyclamen plants grown in 15-cm pots (for the medium-flowered cultivar ‘F₁ K Middy Chorus’) with trickle irrigation and in 9-cm pots (for the small-flowered cultivar ‘F₁ Miracle Deep Rose’) with flood and drain irrigation. It seems that tannin, which inhibits root growth, was inactivated by binding with Fe, and thereby plant growth improved.

View full abstract

The influence of continuous applications of bark compost with different levels of maturity on soil physicochemical properties was investigated during successive cropping of Komatsuna. The soil physicochemical factor such as air filled porosity, total carbon, CEC were measured. Two types of bark composts were used, one was a pre-mature bark compost, which was in the end phase of the primary fermentation stage, and the other was mature bark compost, which was in the second fermentation stage. The growth of Komatsuna was not affected by the maturity or quantity of the applied bark compost. Total carbon, saturated hydraulic conductivity, air filled porosity and CEC increased with the quantity of the applied bark compost and continuous applications of bark compost. The physicochemical properties such as air filled porosity and saturated hydraulic conductivity, CEC correlated with increases in total carbon. Therefore, it was suggested that total carbon is available as an index of the improvement of physicochemical properties of soil. The maturity of the compost did not influence the improvement of physicochemical properties.

View full abstract

Shoots of three-year-old cv. Tonewase and Shinsyu trees under restricted root zone volume were pinched 8–10 days before full bloom (FB), leaving 10 leaves per shoot from their basal part. Lateral buds were repinched at their basal part soon after sprouting. Total shoot lengths per tree and average shoot lengths were shorter in the pinched trees as compared with the non-pinched trees in both cultivars. Shoot pinching did not affect yields per tree, but increased average fruit weights in both cultivars. In Shinsyu trees, shoot pinching decreased total soluble solids contents (TSS) of fruit. On both cultivars, there was little influence on flower bud formation on the mother branch. Shoots of three-year-old cv. Sosyu under pot culture were pinched the 27 days before FB, leaving 8 leaves per shoot. Shoot pinching increased the yields per tree and the average fruit weights, but did not affect fruit quality. There was no correlations between fruit weight and shoot growth in either the pinched trees or the non-pinched trees. Shoots of three-year-old cv. Fuyu trees under pot culture were pinched 2 days before FB at different intensities of pinching. Shoot pinching decreased total shoot lengths per tree, average shoot lengths, leaf numbers, leaf weights and leaf areas per tree. Shoot pinching increased average fruit weights under both intensities of pinching. There were no differences in yields per tree and TSS between the appropriately pinched trees and non-pinched trees, whereas those of the severely pinched trees were inferior to those of non-pinched trees. Shoot pinching did not affect the annual dry matter gains per unit leaf dry weight and per unit leaf area. The ratio of assimilates partitioned into fruit were higher, whereas those into older wood, shoot and fine root were lower in the appropriately pinched trees compared with those in the non-pinched trees.

View full abstract

Characteristics of dry matter production and assimilate partitioning in conventionally cultivated trees, trees that were sheet mulched from Aug.7 (78 days after full bloom) to Dec.18 (harvest time) and trees that underwent trunk girdling on Aug.23 (94 days after full bloom) were determined in 43-year-old satsuma mandarin (Citrus unshiu Marcow.). In the conventionally cultivated trees, the land area occupied by the tree canopy was about 7.4 m² and the leaf area index was about 4. The yield per tree was about 67 kg, that per unit land area occupied by the tree canopy was 9.1 kg·m⁻², and that per unit leaf area was about 2.3 kg·m⁻². There were no significant differences in the land areas occupied by tree canopy, leaf area indices and fruit productivities of sheet-mulched trees and trunk-girdled trees, compared to those of conventionally cultivated trees. Total soluble solids content was highest in sheet-mulched trees, followed by that in trunk-girdled trees, and was smallest in conventionally cultivated trees. In conventionally cultivated trees, annual dry matter gains per tree were about 16.5 kg. The annual dry matter gains of fruit, new leaf, new root, old wood, old root and new shoot were about 10.6, 2.7, 1.3, 0.8, 0.7 and 0.4 kg, respectively. The dry matter gains per unit leaf dry weight and per unit leaf area were about 3.75 g·g⁻¹ and about 560 g·m⁻², respectively. The percentages of assimilates partitioned into fruit, new leaf, new root, old wood, old root and new shoot were about 64, 16, 8, 5, 4 and 3%, respectively. There were no significant differences in the sheet-mulched trees and trunk-girdled trees in the annual dry matter gains per tree and the percentages of assimilates partitioned into each organ, compared with those in the conventionally cultivated trees, except for the percentages of assimilates partitioned into new root, which were significantly smaller. There were no significant differences in the dry matter gains per unit leaf dry weight or per unit leaf area in the sheet-mulched trees and trunk-girdled trees, compared with those of the conventionally cultivated trees.

View full abstract

We investigated the effect of super-high density planting for early recovery from sick soil and low temperature injury in fig (Ficus carica L. ‘Masui Dauphine’) over a five-year period. Towards this end, fig trees were planted at either 0.8 or 2.0 m planting distance (super-density planting), in comparison to the conventional 4.0 m planting distance on the continuous cropping field. It was observed that super-high density planting with 0.8 m was superior to 2.0 and 4.0 m planting distances for maintaining tree vigor and yields under continuous cropping conditions, suggesting the effectiveness of 0.8 m planting distance for early recovery from sick soil. There was no difference in the quality of fruit between trees grown at these two different planting distances. When trees were exposed to low temperature injury in a given year, notable reduction in yield was observed according to the length of the planting distances (i.e. 0.8 m < 2.0 m < 4.0 m). Furthermore, tree vigor and total yield were regained earlier in super-high density planting with 0.8 m planting distance relative to 2.0 and 4.0 m. After two years, the level of yield recovered from the 0.8 m treatment was similar to the yield before the onset of low temperature injury. There was no difference in the quality of fruit between trees grown at these two different planting distances. The results of this study indicated the effectiveness of 0.8 m planting distance for early recovery from sick soil and low temperature injury in fig cultivation.

View full abstract

We have developed a new culture method to increase the efficiency of asparagus (Asparagus officinalis L.) harvesting in maintaining mother stem cultivation. In this culture method, the young spears, which ultimately grow to form mother stems, are bent back towards the ridge and planted in a line. The mother stems are then separated from the shoots. We studied the effect of this culture method on yield. This culture method resulted in a decrease in the yield by 24% when compared with the yield obtained from the control. Low light interception, which was considered to be the cause of the decreased yield in this community, can be attributed to the fact that the bent mother stems were in close proximity to the stems on the adjoining ridges. However, light interception increased when the mother stems were drawn to the passage and bent at an angle of 30°. With this culture method, the spear yield in the following year showed a total yield of 96% compared to the yield obtained from the control. Further, the time required for harvesting was 24% less and harmful stem postures that required immediate improvement (AC4) were 60% less frequent than those in the control. These findings suggest that our culture method will improve harvesting conditions.

View full abstract

Effects of leaf-fruit ratio (LFR) on yield, fruit quality, cluster formation and fruit set were investigated to determine the optimum fruit load in Mango (Mangifera indica L.) cv. Aikou in comparison with that of cv. Irwin under pot culture (soil volume of about 25 liters per pot) in a plastic greenhouse. In a given year, yields per tree with LFR 40 and 60 were higher than that with LFR 80 in cv. Irwin, whereas that with LFR 20 was higher than those with LFR 40 and 60 in cv. Aikou. In both cultivars, fruit numbers per tree decreased and average fruit weights increased with increase in LFR. LFR did not affect fruit quality (total soluble solids content, organic acid content, fruit firmness and fruit skin color) in cv. Irwin and cv. Aikou. In the following year, the number of seeded clusters per tree and the seeded fruit number per tree were not affected by LFR of the previous year in cv. Irwin, whereas the number of seeded clusters per tree in trees with LFR 20 in the previous year was lower than that in trees with LFR 40 or 60 in the previous year in cv. Aikou. LFR of the previous year did not affect yield and fruit quality in cv. Irwin. In cv. Aikou, yield of trees with LFR 20 in the previous year was lower than those of trees with LFR 40 or 60 in the previous year. However, LFR did not affect fruit quality. It was considered that the optimum LFR for fruit production of approximately 600 g was 40–60 for cv. Aikou under pot culture.

View full abstract

Effects of gibberellin (GA) and 6-benzilaminopurine (BA) combined application and the effects of GA application and day length on flower induction in Odontioda orchid were investigated in experiment 1 and 2, respectively. In experiment 1, BA application did not affect spiking of Odontioda, but the spiking percentage was increased to about 90% by sole application of 100 ppm of GA₃. In experiment 2, the spiking percentage under night break treatment was less than that of a 10-h day length. However, 100 ppm of GA₃ application increased the spiking percentage up to 80% regardless of the difference in day length. Thus, it was demonstrated that sole application of 100 ppm of GA₃ significantly improved the spiking of Odontioda orchid.

View full abstract

We examined the use of local heating with air ducts hung above cultural beds to reduce fuel consumption in winter greenhouse tomato production. In order to clarify the economic and physiological effects of local heating, we compared a local heating system using hanging air ducts to supply warm air to shoot apices and flower clusters, with a control using conventional air ducts on the ground. Differences in surface vertical temperature distributions at night, fruit yield, and fuel consumption were investigated. By local heating, the upper air and plant surface temperatures at night were slightly higher than those in the control, but temperatures of lower air and plant surface were considerably lower. The commercial fruit yield by local heating tended to be greater than those in the control because of a high ratio of intact fruit and a higher fruit weight from plants exposed to local heating. Fruit grown by local heating had a higher ratio of locule tissue. The local heating system used 26.2% less fuel per unit area than the control.

View full abstract

The effect of irradiance and duration with far-red (FR) light at the end of the day (EOD-FR) on stem elongation of spray type chrysanthemum was investigated with two cultivars, ‘Sei Prince’ and ‘Remidas’ in order to reduce the growing period for cut flower production. When plants were exposed to FR light for one hour, stem elongation tended to shorten as irradiance decreased from 0.19 to 0.07 W·m^-2. In ‘Remidas’ stem length under weak irradiance (0.07 W·m^-2) was significantly shorter than that under strong irradiance (0.19 W·m^-2). When plants were exposed to FR light under weak irradiance (0.06 W·m^-2), stem elongation tended to be promoted as irradiation time increased from one hour to three hours. It is considered that stem elongation can be promoted under weak FR light irradiance conditions when irradiation time increased. In ‘Sei Prince’ and ‘Remidas’, stem elongation was promoted more than 15% on comparison between plants without treatment and plants exposed to FR light with 0.03 W·m^-2, for two or three hours at the end of the day.

View full abstract

α-Ketol linolenic acid (KODA, or 9-hydroxy-10-oxo-12(Z),15(Z)-octadecadienoic acid) was previously isolated from Lemna paucicostata. In a previous study, it was reported that KODA promoted flowering in several kinds of plants. In the present study, the effect of KODA on flowering in one-year-old satsuma mandarin (Citrus unshiu Marc.) trees on trifoliate orange rootstocks was examined. During exposure to low autumn temperatures, which are floral inductive, satsuma mandarin trees were treated with KODA at different stages. After defoliation and transferring plants to a high temperature (25°C) room, the number of flowers was counted. With an increase in exposure to low autumn temperatures, the number of flowers after defoliation at 25°C increased both in non-treated and KODA-treated trees. On October 30, the number of flowers after defoliation at 25°C was higher in trees that had been sprayed with KODA before October 10 compared to that in non-treated trees. The increase in the number of flowers following KODA treatment was accompanied by an increase in the number of sprouting nodes. Under continuous warm-temperature (25°C), which was not floral inductive, KODA treatment had no effect on the number of flowers after defoliation at 25°C. These findings suggested that KODA treatment under floral inductive conditions could promote flower-bearing in satsuma mandarin. In addition, it was suggested that the principal cause of the increase in flower bearing by KODA treatment was the promotion of axillary bud sprouting. However, KODA treatment tended to exhibit a limited effect on flower bearing when the number of chilling hours have been insufficient.

View full abstract

The present study aimed to clarify the relation between elasticity index and water loss. Fruit ripeness was maintained by low-temperature storage without changing the physical properties of the fruit, although the water content changed due to low-humidity. ‘Le Lectier’ pears harvested at a commercial maturity were stored in a simplified snow storeroom at 2–3°C with 95% or more relative humidity or in a refrigerator at 2°C with 10% relative humidity. The amount of water loss, flesh firmness and elasticity index of the fruit stored in the simplified snow storeroom did not change during storage. However, the amount of water loss and elasticity index of the fruit stored at 2°C with a 10% relative humidity markedly decreased, and flesh firmness decreased slightly due to water loss. A significant correlation between the amount of water loss and elasticity index was apparent in the low-humidity processing. However, the correlation between the water content and elasticity index in high humidity processing was not apparent because the application width was small. These findings indicate that the decrease in the elasticity index of ‘Le Lectier’ pears was caused by fruit softening and water loss.

View full abstract

The elasticity index (EI) determined by a resonant frequency method for ‘Fuyu’ persimmon after the harvest decreased in a consistent manner despite the harvest time. By a sensory test, the optimum ripeness by EI was determined to range from 30.202 to 13.563 × 10⁶ cm²·Hz². A predictive formula for optimum ripeness was constructed using a reciprocal equation. The beginning of the optimal ripeness period (t₁) = {9.386(30.202 − Y₀)}/{0.830(Y₀ − 30.202) − Y₀}, the end of the optimal ripeness period (t₂) = {9.386(13.563 − Y₀)}/{0.830(Y₀ − 13.563) − Y₀}, where Y₀ is EI at 0 after harvest and substitutes mantissa of the scientific notation. The error between this predicted value and the observed one ranged from 0.5 to 1.3 days for the beginning of optimal ripeness period and from 0.7 to 3.5 days for the end of the optimal ripeness period, suggesting that the formula is practical to predict the range of optimal ripeness of ‘Fuyu’. However, further examination is necessary to construct a predictive formula with high precision. For the flesh texture of ‘Fuyu’ persimmon, EI drastically decreased before the optimal ripeness time and the texture index (TI) decreased thereafter, suggesting that both parameters reflect different inner qualities of persimmon fruit.

View full abstract

The optimum conditions and mechanisms of inducing disease resistance by heat shock were investigated against gray mold (Botrytis cinerea) in cucumber (Cucumis sativus L.). The growth of inoculated mycelium was controlled most effectively by treatment at 40°C, for 2 minutes. Salicylic acid accumulated in the treated leaves under this condition and two peaks were obtained 24 and 96 hours after treatment. A pathogenesis-related protein, peroxidase gene (POX; M91372), was also expressed in the treated leaves and showed two peaks at 24 and 96 hours, respectively after treatment. Partial heat shock treatment was conducted by dipping only the first leaf of two leaves seedlings. Resistance and POX expression were induced not only in the treated leaves but also in the untreated second leaves. In conclusion, heat shock by means of hot water dipping could induce resistance against gray mold in cucumber. Systemic acquired resistance may have been obtained by some possible pathway.

View full abstract