Cross compatibility between Hydrangea serrata (Thunb.) Ser. and Hydrangea macrophylla (Thunb.) Ser., adequate conditions for ovule culture for their hybridization, and cross compatibility among hybrid individuals were examined. Seed formation did not occur in hybridization between H. serrata and H. macrophylla when H. serrata was used as the seed parent; however, a high rate of seed formation was confirmed using H. macrophylla as the seed parent. Individual hybrids could be acquired with ovule culture for most cross combinations between cultivars of H. serrata and those of H. macrophylla. To efficiently acquire hybrid individuals by interspecific crossing with ovule culture, the culturing ovules had to be passed 60 days after crossing and cultured in 1/2 MS (made by Murashige and Skoog) medium with the addition of gibberellin (GA₃) 1 mg·L⁻¹. Individual hybrids were acquired with ovule culture in all cross combinations when hybrid plants between H. serrata and H. macrophylla were crossed with cultivars of H. macrophylla or those of H. serrata.

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Komatsuna ‘Natsurakuten’ was cultivated during three successive crop seasons (early summer, late summer, autumn) in the same soil consisted of andisols in a greenhouse. Four fertilization formulae were tested in order to reduce nitrate concentration in plants. The amount of nitrogen (N) fertilizer in the control fertilization (N7) was 7 kg·10 a⁻¹. In fertilizations based on soil diagnosis of nitrate-N before fertilization, the summed amounts of N-fertilizer and soil nitrate-N were 7 or 5 kg·10 a⁻¹. The other fertilization (N0) was formulated without N-fertilizer. Using the fertilizations based on soil diagnosis, nitrate concentrations in plants were hardly changed compared with those using N7 in the summer, but these concentrations were lower than those of N7 in the autumn. However, nitrate concentrations in N0 were much lower than those of other fertilizations. We gained sufficient yields with N0 when the length of cultivation was prolonged by 5 days in late summer. About 3 kg·10 a⁻¹ organic N was mineralized during cultivation in summer, and this amount was higher than the amount of N assimilated in plants. Thus it is necessary to consider the amount of mineralized N and assimilated N in plants in order to reduce nitrate concentration in plants during high temperatures.

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By mulching non-woven fabric sheets on the surfaces of root zone soils of sweet cherry trees (cultivar: Satoh Nishiki), and by stretching PVC films measuring 70 cm in width vertically around the circumference, rain water was prevented from reaching the soil (Soil Covering, SC). Fruit cracking, soil moisture, plant water relation, leaf character and fruit growth and quality in SC were compared with that under a rain shelter (RS) and that of open culture (Cont. ). At harvest time, fruit cracking (%) in SC was lower than Cont. By overhead sprinkling, fruit cracking in SC was remarkably lower than that in Cont. When soil moisture and plant water relation were measured, moderate water stress was found in SC, but water stress was stronger than that in Cont. Mean fruit lateral diameter during the latter half period in the third stage of fruit growth in SC was significantly smaller than that of the other two plots. Measurements of fruit diameter displacements during this period showed more frequent fruit contractions in SC than in Cont. Shade leaf phenomenon and less coloring on the fruit surface was observed in RS. These problems were not found in either SC or Cont.

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The effect of planting density (varying form 330 to 3178 trees·ha⁻¹) on net production rate (NPR: t DW·t⁻¹ DW·y⁻¹) defined as the production efficiency of leaves was studied in ‘Starking Delicious’ apple trees (Malus domestica Borkh.) on M.9, M.26, M.7 and MM.106 without pruning. On all rootstocks, fruit NPR (Fd/Ld) and total NPR (⊿Pn/Ld) decreased as planting density (ρ: no. of trees·ha⁻¹) increased, but NPR of branch, trunk and root (⊿Pb/Ld, ⊿Pt/Ld and ⊿Pr/Ld) increased. The density effects on Fd/Ld, Z/Ld (Z indicates ⊿Pb, ⊿Pt or ⊿Pr) and ⊿Pn/Ld could be represented respectively by Fd/Ld = K₁ exp (−k₁ρ), 1/(Z/Ld) = A₃ + B₃/ρ and ⊿Pn/Ld = K₂ρ^−k2. The relationships between fruit NPR (Fd/Ld) and total NPR (⊿Pn/Ld) or partitioning ratio into fruit (Fd/ ⊿Pn) could be represented by the following equations: ⊿Pn/Ld = 0.66(Fd/Ld) + 2.8 and Fd/ ⊿Pn = 0.2(Fd/Ld) + 0.07. Also, the fruit NPR was negatively correlated with vegetative net production and partitioning ratio into vegetables. Among the three parameters of vegetative NPR, vegetable net production and partitioning ratio into vegetables, there was a positive correlation. The relationship between total NPR (⊿Pn/Ld) and leaf production (Ld) could be represented by ⊿Pn/Ld = 5.4 exp (−0.08Ld). The relationships between fruit production (Fd) and leaf production (Ld) or fruit NPR (Fd/Ld) could be represented respectively by Fd = −a₁(Ld)² + b₁(Ld) + c₁ and Fd = −a₂(Fd/Ld)² + b₂(Fd/Ld) + c₂. When fruit production (Fd) and leaf production/fruit NPR (Ld/(Fd/Ld)) were plotted as log~log coordinates, Fd increased as Ld/(Fd/Ld) increased, and showed the maximum at a specific Ld/(Fd/Ld) (optimum Ld/(Fd/Ld)). On all rootstocks, the log Fd~log Ld/(Fd/Ld) relation corresponded to the log Fd~log ρ and log Fd~log (⊿Pn/(Fd/ ⊿Pn)) relations. There was also a positive correlation among the three parameters defined as ρ, Ld/(Fd/Ld) and ⊿Pn/(Fd/ ⊿Pn). We conclude that the density effect on fruit production is a phenomenon with a series of following causal relations: change in planting density → change in Ld/(Fd/Ld) → change in ⊿Pn/(Fd/ ⊿Pn) → change in fruit production.

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Using ‘Beni Shimizu’ peach (Prunus persica (L.) Batsch) trees maintained by light pruning with heavy disbudding (LP) or conventional method (CM) as heavy pruning with no disbudding fruit development was investigated in relation to the occurrence of reddish-pulp for four years. Fruits harvested from LP trees had a higher rate of reddish-pulp development, whereas in fruits harvested from CM trees the percentage was low, irrespective of the year surveyed. LP trees resulted in greater yield compared to CM trees. Nitrogen content in the flesh of fruits was significantly higher in LP trees than in those of CM trees during stage 1 of fruit development. When carbohydrate concentrations in the cane and root of LP and CM trees were compared between before and after full bloom, the former trees showed a greater decrease than the latter. Throughout fruit development, the diameter of cells in the flesh of fruits from LP trees was significantly larger than those from CM trees. Besides, the fruit growth rate was greater in the former than in the latter at stage 3 of fruit development. Fruits harvested from LP trees attained higher weight than those from CM trees. Total soluble solid contents of the juice in fruit harvested were significantly higher in LP trees than in CM trees. In LP trees, shoot growth ceased by the beginning of stage 2 of fruit development, while in CM trees, shoot growth continued until stage 3. In LP trees, anthocyanin concentration in the flesh of fruit increased rapidly just before harvest. Total phenolic concentration in the flesh was higher in fruits from LP trees than in those from CM trees throughout fruit development. Further, there was a higher L-phenylalanine ammonia-lyase (PAL) activity in fruit from LP trees than in those from CM trees. Based on these results, the relationship between pruning levels and the occurrence of reddish-pulp in peach fruit is discussed.

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The relation between new shoot growth and the utilization of stored assimilates (nitrogen and carbon) was investigated. A one-year-old apple tree (‘Fuji’ on Malus prunifolia (Willd.) Borkh.), after pruning, was treated with ¹⁵N and ¹³C in the year prior to the experiment. The trees were examined early (in May), at mid-term (June) and when mature (September). Shoot growth stages and nitrogen and carbon status were analyzed at each harvesting. The shoot length did not relate with its position and difference in the length of the shoots was small in May, but thereafter the upper shoots grew longer than the lower shoots. There was no relationship between the length of the shoot and the ¹⁵N excess% of the shoot at each stage, but the value of the ¹⁵N excess% of the shoots in September was much lower than that in either May or June. The ¹³C excess% decreased during the period from May to June, and a limited inverse correlation was found with the length of the shoot. There was a significant positive correlation between the lengths of the shoot and ¹⁵N or ¹³C distribution in the shoot. It was suggested that, as they grew, the longer shoots absorbed higher amounts of stored assimilates than the shorter shoots. Although the degree to which stored versus current absorbed assimilates contributes to new shoot growth might be the same in all shoots, stored nitrogen plays an important role in new shoot growth.

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The effects of temperature on pollen germination and daytime heating on the number of seeds, yield and quality of fruits were examined in eggplant ‘Senryo’ forcing culture during the winter season. Incubation at 25°C for more than one hour effectively promoted the pollen germination rate and pollen tube elongation on agar culture. The number of seeds, fruit yield and quality of after artificial pollination were significantly higher in the green house heating at 25°C for 3 h from 11:00 to 14:00. Pollination using bumblebees during one hour of daytime heating did not increase total fruit yield, but slightly raised fruit quality. These results indicate that pollination during daytime heating is effective in increasing fertility and fruit yield in eggplant forcing culture during the winter season.

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A method of suppressing sprouting in Budousanshou (Zanthoxylum piperitum (L.) DC. f. inerme Makino) due to early defoliation in the fall by diseases and pests was investigated. We used three plant growth regulators naphthaleneacetic acid (NAA), ethychlozete and maleic hydrazide (MH) to suppress sprouting. Ethychlozete has been used to suppress sprouting in Satsuma mandarin (Citrus unshiu Marcow.) in green house cultivation. Budousanshou belongs to the same family as Satsuma mandarin. NAA and MH have been tested with other citrus species. Nine days after the application of the plant growth regulators, trees were hand-defoliated and stems were sampled for bud sprouting. Sprouting days and percentages in the experimental field were investigated by the stem cutting method using sampled stems. Trees treated with 200 ppm NAA exhibited maximum number of days to sprouting with sprouting being suppressed for approximately 30 days. In the stem cutting method sprouting stem percentage was 0%. In the experimental field sprouting percentage was also low with 9%. Our study suggests that treatment with 200 ppm NAA is highly effective for suppressing fall sprouting, and is of practical importance in fruit production.

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Effects of the winter night temperature (11°C or 16°C) and the photoperiod (natural day length or 16 hr) on the growth and flowering of snapdragons (Antirrhinum majus L.) with different earliness were investigated. Seeds of a Group II cultivar ‘Light Pink Butterfly II (LPB II)’ and a Group III cultivar ‘Light Pink Butterfly III (LPB III)’ were sown in August and seedlings were pinched in September. The 16 hr long-day treatment from the end of September increased the plant height of ‘LPB III’. Long-day treatment decreased the number of days to flowering and increased the yield of cut flowers branched from the first node shoots and the cotyledon node ones in ‘LPB II’, and similar results were obtained in ‘LPB III’ which were grown under 16 hr long-day and 16°C night temperature. Throughout the growing period, length of cut flowers harvested from ‘LPB III’ was longer than that from ‘LPB II’. In conclusion, the long-day treatment combined with 16°C night temperature was effective for decreasing the number of days to flowering and increasing the yield of cut flowers of ‘LBP III’ in winter.

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Ascorbic acid content is an important factor in spinach (Spinacia oleracea L.) quality. In this study, we investigated the number of days after the removal of shading material that would be required to increase the ascorbic acid content of spinach grown under shade to the same level as that in spinach grown without shade. We also investigated the factors responsible for increased ascorbic acid content after the removal of shading material. The ascorbic acid content in spinach grown under shade was at least 30% lower than that of spinach grown without shading. However, the ascorbic acid content of the shaded spinach reached the same level as in spinach grown without shade 2 to 3 days after the removal of shading material during a sunny period. After the removal of shading material, the water content in the spinach plant decreased and the ascorbic acid content increased on both a fresh-weight basis and dry-weight basis. In a growth chamber experiment, ascorbic acid content increased on both a fresh weight and a dry weight basis 1 day after changing the light intensity from low (160 μmol·m⁻²·s⁻¹) to high (390 μmol·m⁻²·s⁻¹). These results suggest that both the decrease in water content and the increase in ascorbic acid synthesis contribute to the increased ascorbic acid content in spinach plant after the removal of shading.

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Proper methods of long-day treatment using incandescent lamps for winter and spring shipping of Eustoma grandiflorum were examined. Ten Eustoma cultivars were planted in a greenhouse on October 8, 2004. One-half of the plants were given night break treatment for 4 h starting immediately after planting until flowering, the others were grown under ambient day length of 10-12 h (the control). The mean flowering date (anthesis of the first floret) of each cultivar with night break treatment was 22-49 d (mean 35 d) earlier than that of the controls. ‘Nail Peach Neo’ seedlings were given night break treatment for 5 h during five developmental stages: from planting to pistil formation, pistil formation to flowering, flower budding to flowering, flower bud initiation to flowering, and planting to flowering. The time from planting to flower budding of plants under night break treatment from planting to flowering and from planting to pistil formation were 50 d and 53 d, respectively, compared to 66 d in the control. However, the time to flower budding in plants in which night break treatment started after pistil formation was the same as that in controls. The time from flower budding to flowering of plants under night break treatment from planting to pistil formation was 47 d, but there was no significant difference in this time period between other treatments and controls (54 d). As the flowering time of treated plants was earlier, the number of nodes on the main stem at the anthesis of the first floret was reduced. Plants that were illuminated for 5 h at night were divided into three treatments: night break, pre-dawn lighting and end-of-day lighting. The time from planting to flower budding of plants receiving both night break and pre-dawn lighting treatments was 52 d, whereas that in plants given end-of-day lighting this time was 58 d, compared to the control of 65 d. It was concluded that to promote flowering for winter and spring shipping, night break or pre-dawn lighting using incandescent lamps should be applied to Eustoma plants from planting to pistil formation.

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This study was conducted to investigate infestation of thrips in mother fern green asparagus (Asparagus officinalis L.) cultivation and the effects of near ultraviolet ray-absorbing (UVA) film. The most harmful thrips species for asparagus was onion thrips (Thrips tabaci Lindeman) in the southwestern warm regions of Japan. Most of these species were detected in the upper parts of mother ferns in the beginning of mother fern establishment, whereas they were recognized in the lower parts thereafter. These species were parasitic on fresher leaves. The infestation of these species increased remarkably in May and increased promptly when insecticide was not sprayed until the middle of August. Use of UVA film caused a remarkable decrease in thrips, making the film useful for controlling damage and reduction of pesticide application in mother fern green asparagus cultivation.

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This study was carried out to investigate the effects of near ultraviolet ray-absorbing (UVA) film on growth and yield in mother fern green asparagus (Asparagus officinalis L.) semi-forcing cultivation. We also evaluated the durability of its ability to absorb near ultraviolet rays. Comparing the effects of using polyethylene and UVA film showed few differences in the values of illuminance, temperature, yield, color and brix of spears in the green house. The ratio of growth in the main stem was increased and the number of branches was decreased by pinching off the top when the plants were cultivated in a green house covered with UVA film. The ability of UVA film to absorb near ultraviolet rays decreased each year.

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This study was conducted to develop a new growing system that combines high density planting and fertigation of grapevines in order to achieve early establishment, and increased production of high quality fruits. Characteristics of the new system include; 1) absence of root restriction, 2) planting more than 800 per 10 a of own-rooted vines, 3) mulching under a canopy of water-proof plastic sheeting, and 4) supply of water and nutrient solution automatically using equipment comprised of an irrigation system, nutrient solution mixing machine and drip tubes. Both ‘Pione’ and ‘Aurora Black’ grapevines (Vitis labrusca × V. vinifera) yielded fruits as well as mature vineyard in the second year after planting. When the effects of shoot density on fruit quality and yields of grapevines under this system were investigated, fruits with superior berry size, sugar content and skin color were produced with a combination of 15 clusters and 10 to 20 shoots per meter of fruiting cane. Based on fruit quality and yields obtained over three years periods, we developed a standard model for irrigation and fertilization year-around year.

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We investigated inhibitory effects of the formation of axillary flower buds by pinching and defoliation of current shoots on four different cultivars of Japanese pear (Pyrus pyrifolia (Burm. f.) Nakai), to save labor for disbudding on the main one-year shoot of the scaffold branch. In ‘Housui’, the average rate of axillary flower bud formation was normally 86-95% in 2002-2004, but by pinching one-third off the shoot 50-65 days after full bloom, the rate in treatment was reduced to 40-54%. Further, the secondary growth of shoots was promoted by earlier pinching treatment, and the flower buds formation was more effectively inhibited by secondary growth. In ‘Shinko’, ‘Kousui’ and ‘Shurei’, the earlier pinching treatment caused the same results as ‘Housui’, which inhibited the formation of axillary flower buds. The bud formation was especially inhibited not only in the part showing secondary growth but also in that showing first growth. The defoliation treatment 50-65 days after full bloom inhibited the formation of axillary flower buds in ‘Shinko’ only. Thus, these findings suggest that the earlier pinching and defoliation treatment of current shoots can be a technique to control flower number as the working period does not compete with the disbudding period.

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The growth of taproot of carrot (Daucus carota L. cv. Natumaki-senkogosun) cultured under hydroponics was investigated. Plants were cultured in boxes containing half strength Enshi solution. Keeping the solution surface level about 7 cm below the base of the root, aeration was performed at 0 (non-aerated), 5 and 60 minutes in each 1-hour cycle. Though the weight of storage root was not influenced by the aeration period, the length of swelling in the root axis increased with the aeration period (Exp. 1). The taproot was grown in a shallow box with a mesh bottom suspended in a large case containing the same solution as used in Exp. 1. The nutrient solution was continuously aerated. The weight and length of the swelling of taproot not submerged in solution were larger than those of submerged taproot. A high rate of root cracking occurred in the submerged taproots (Exp. 2).

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To identify factors involved in seed development of parthenocarpic tomato, the effects of combinations of crossing parents and crossing stage on seed development of parthenocarpic tomato were examined. And the ovary size of parthenocarpic tomato before and after the flowering stage was compared with that of non-parthenocarpic tomato. When the seed parent was the non-parthenocarpic tomato cultivar ‘Momotaro york’, the seeded fruit rate was 100% irrespective of the pollen parent, there were about two hundred seeds per fruit. When the seed parent was the parthenocarpic tomato pure bred strain ‘PASK-1’ or ‘PF-811K’, the seeded fruit rate was 72~94% irrespective of the pollen parent, there were 7.6~29.9 seeds per fruit. Therfore, it was suggested that seed development of parthenocarpic tomato was affected by the seed parent irrespective of the pollen parent, and seeds were apt to remain undeveloped when the seed parent was parthenocarpic. Concerning artificial crossing stage on seed development of parthenocarpic tomato, the seeded fruit rate of non-parthenocarpic tomato cultivar ‘Momotaro york’ was 100% irrespective of artificial crossing stage, and the numbers of seeds per fruit of ‘Momotaro york’ remained standard. The seeded fruit rate of ‘Renaissance’ two days after flowering was 8% in spring and 33% in autumn. Those values were very low compared with 96% in spring and 87% in autumn on flowering. And the numbers of seeds per fruit of ‘Renaissance’ were as few as 0.8 in spring and 4.0 in autumn. Furthermore, the ovary of ‘Renaissance’ from bud stage to two days after flowering enlarged successively in length and breadth. Accordingly it was suggested that the decline of seed development faculty of the parthenocarpic tomato cultivar ‘Renaissance’ by two days after flowering was not influenced by the decline of fertilization faculty of pistil, but the expression of parthenocarpy before flowering.

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