For the purpose of producing own-rooted nursery trees of mango (Mangifera indica L.), several factors affecting rooting of air-layered mango using to 13- to 21-year-old ‘Irwin’ and 8- to 11-year-old ‘Aikou’, and cultivar differences in rooting abilities using fifteen 8-year-old cultivars and 5-year-old ‘Irwin’ and ‘Aikou’ were investigated. Auxin solution (50% ethanol) was sprayed on the girdle (2–3 cm width) of the air-layered branch. In both cultivars (‘Irwin’ and ‘Aikou’), the rooting percentage (after two months of air layering) of air layers treated with NAA tended to be superior to those of air layers treated with IBA. However, there was no significant difference between two auxins in the root number or total root length per rooted air layer. In both cultivars, there was no rootings in controls not treated with auxin. The rooting percentage of air layers treated with NAA 1,000 ppm tended to be low in both cultivars. The total root length of air layers treated with NAA 2,000 ppm was longer than that of air layers treated with NAA 1,000 ppm. It was considered that the optimal concentration of NAA for rooting was 2,000 ppm in both cultivars. In both cultivars, the rooting percentage of air layers tended to decrease when additional treatment of NAA was performed. In ‘Irwin’, the root number and the total root length was significantly decreased by additional treatment with NAA. Combination of NAA 2,000 ppm and ABA 20 or 100 ppm did not affect rooting of air-layered ‘Irwin’. In both cultivars, branch age did not affect rooting. Removal of cambium did not affect rooting of air-layered ‘Aikou’. In both cultivars, air-layered shoots with many leaves tended to be higher in the rooting percentage, and were significantly high in the root number and total root length than those of air-layered shoots with few leaves. Water content (20–40%) in the rooting medium did not affect rooting of air-layered ‘Aikou’. In both cultivars, a suitable time for air layering to obtain rooting seemed to be July to August. In seventeen cultivars, ‘Spirit of 76’ showed the highest rooting ability, followed by ‘Aikou’, ‘Irwin’, ‘Khom’ and ‘Glenn’; The rooting ability of ‘Sensation’, ‘Golden Lippens’ and ‘Dot’ was slightly low, and that of ‘Lippens’, ‘Tommy Atkins’, ‘Florigen’ and ‘Valencia Pride’ was low. Air-layered ‘Alphonso’, ‘Edward’, ‘Florigon’, ‘Khieo Sawoei’ and ‘Nam Doc Mai’ did not root at all.
Utility and function of porous clay pots for a root-zone environmental control system (RECS) were investigated. The porous clay pots characteristically had no drainage hole at the bottom. Growth and flowering of pansies in the porous clay pots with pot-surface watering were compared with those in plastic pots with top watering or capillary mat watering. The porous clay pots were placed in a plastic water bath to supply water though pot-surface. In addition, effects of pot soils and of water levels in the bath on the rate of soil moisture were investigated. Pansy growth was significantly stimulated in the porous clay pots compared with those of plastic pots. The root-zone temperature in the porous clay pots was lower than the air temperature during the day time. These findings indicate that the porous clay pot with pot-surface watering is useable as watering equipment for RECS. The rates of soil moisture changed depending not only on soils but on water levels in the bath. However, it was suggested that soil moisture in the porous clay pot should be controlled by regulating water level in the bath.
We examined the absorption and transfer of dioxins from the soil to cucumber, zucchini, carrot, and daikon (Japanese radish). Dioxins were detected in all the vegetables examined, although the amounts detected in the roots and shoots were extremely small. The amounts of dioxins absorbed by roots from the soil and transferred to shoots were relatively large in zucchini. Dioxins were also detected in the transpiration fluid from zucchini.
To develop simple and versatile fertilizer management in cultivation by fertigation of carnations (Dianthus caryophyllus L.), the effects of fertilizer management by apparent nitrogen absorption concentration on cut flower yields, characteristic form and soil solution concentration were investigated using the cultivar ‘Nora’. Cut-flower yield by the four-split (seasonally-split) application method was highest among treatments and that by the twelve-split (monthly-split) application method was higher than that of the fixed application method. The cut flower weight (g)/length (cm) ratio of the fixed application method was smaller than that of the twelve-split application method between 33 and 36 weeks after the beginning of harvest. There were differences in EC and nitrate nitrogen concentration between the different methods of treatment. The nitrate nitrogen concentration of soil solution in each treatment ranged from 8 to 169 ppm, from 54 to 103 ppm, and 21 to 108 ppm for the four-split, twelve-split and fixed application methods, respectively, 20 weeks after the beginning of harvest. Fluctuation in the fixed application method was the greatest among the treatments, fluctuation in the four-split application method was least among the treatments examined, and the nitrate nitrogen concentration of soil solution was maintained at an optimal concentration level for the growth of carnations throughout the cultivation period.
This study investigated the changes in leaf water potential (ΨL) and photosynthetic rate (Pn) of cropping and non-cropping blueberry plants grown under drought and re-watering conditions. Nine-year-old ‘Tifblue’ plants grown in a pot were used. When plants grown under drought conditions, ΨL and Pn of leaves decreased as soil water content decreased. Pn decreased to near zero when ΨL was approximately -3.5 MPa and soil water content was approximately 8%. Under that condition, all fruits and some shoots wilted and some fruits dropped. Pn of cropping plants decreased more rapidly than that of non-cropping plants, under drought conditions. After re-watering, ΨL and Pn of plants grown under drought conditions were increased and then these values reached half the level of plants grown under well-watered conditions. The rate of increase in Pn in cropping plants was slower than that in non-cropping plants under drought conditions. The values of stomatal conductance and transpiration rate showed a tendency similar to that of Pn. These results showed that the critical point of ΨL for recovering plant vigor was less than -3~-3.5 MPa. Furthermore, drought stress was promoted by fruit loading.
Effective root pruning treatment for recovery from carnation stunting and shoot proliferation (CSP) syndrome was investigated. In the first experiment, the amount of root pruning and soil environment of the plant after pruning were changed. The result showed that it was important to remove eighty percent of roots, to transplant seedlings under conditions of adequate soil moisture and cool soil temperature, and to produce several new roots to recover from CSP syndrome. Then, the effects of pruning timing (late August or late September) and symptom severity at the time of pruning on the recovery and yield of cut flowers were determined. The results showed that timing of pruning had no significant effect on the yield but early recovery of plants was observed when root pruning was done in late August. Plants that received root pruning during the mildly symptomatic stage of CSP syndrome showed earlier recovery than plants that received root pruning at severely symptomatic stage, and produced the same level of cut flowers as healthy plants until late March when root pruning was performed in late August. The present results indicate that, in carnation-producing centers in warm areas, root pruning treatment is effective for recovery from CSP syndrome when most roots were removed at the mildly symptomatic stage of CSP syndrome, despite the under high temperature conditions in late summer.
To clarify the influence of different levels of greenhouse ventilation on cucumber growth and yield under forcing culture, we grew ‘Natsunokaori’ cucumber plants grafted onto ‘Yuyu Ikki (Black)’ squash rootstock under two culture conditions in which the air temperatures in the greenhouses between 8:00 and 13:00 were adjusted to 25°C (L treatment) and 30°C (H treatment) by varying the amount of ventilation. Four training methods were used. As a result, fruit growth was suppressed and leaf development was promoted at 25°C (L treatment), but there was no difference in the total number of lateral branches, harvested fruits and marketable fruits between the two culture conditions. As for training methods, wire-training and leaving three second-lateral branches unpinched yielded a greater number of harvested fruits and higher marketable yields than the other training methods. Furthermore, training work was simplified. Therefore, these training methods appeared suitable for forcing cucumber culture.
In four highbush blueberry cultivars ‘Spartan’, ‘Bluecrop’, ‘Darrow’ and ‘Dixi’, quality of fruit harvested by individual and cluster was evaluated at harvesting and 14 days after storage (14 DAS). Individual harvesting picked the berries one by one, when the surface color became blue. Whereas cluster harvesting cut the peduncle of cluster when the surface color of 70~80% of fruits in the cluster turned blue. At harvesting, fruit weight was smaller and variations in fruit weight, fruit firmness, soluble solid content and titratable acidity were higher in cluster harvesting compared with those of individual harvesting. At 14 DAS, reduction rates of each trait in cluster harvesting, which decreased from harvesting to 14 DAS and the appearance of the fruit surface did not demonstrate shrink age. On cluster harvesting, ‘Bluecrop’ and ‘Darrow’ were characterized by limited variation in fruit weight at harvesting and limited rates of reduction in fruit weight, fruit firmness and titratable acidity during storage, while the strength of fruit setting was large. As a result, the fruits in cluster harvesting were not of uniform quality at harvesting but fruit quality maintained a longer shelf-life. ‘Bluecrop’ and ‘Darrow’ are available as cluster harvesting.
To develop methods of predicting the harvesting date for Japanese chestnut cv ‘Tanzawa’, ‘Tsukuba’ and ‘Ishizuchi’, full flowering and harvesting dates recorded for 44 years (1965–2009) were analyzed. There were positive correlations between the harvesting dates and full female flowering dates. Predictive formulas to calculate harvesting dates were obtained from the regressions. The RMSEs (root mean square error) were 4.3–4.9 days. There were inverse correlations between the number of days to maturity and the mean air temperatures for about 30 days from full female flowering dates. A second predictive formula of harvesting dates was obtained from the regressions. The RMSEs were 3.7–5.0 days. There were positive correlations between the number of days to maturity and the mean air temperature for a specific time in the late maturation period. A third predictive formula was obtained from the regressions. The RMSEs were 3.0–3.3 days. A practical technique consisting of three steps was developed as a method of predicting the harvesting date for Japanese chestnut.
Effects of the shape and volume of plugs, duration of raising runner plants, and soil nitrogen concentration before planting on the initial growth, development of terminal and axillary inflorescences, and fruit yield in plug-grown ‘Akihime’, ‘Tochiotome’ and ‘Benihoppe’ strawberry plants were investigated to develop a technique for division of labor between raising runner plants and fruit production in strawberry forcing culture. Runner plants excised from the mother plant formed root clumps in 20 days when grown in the round-type 72-cell plug tray (37 mL/cell) for all 3 cultivars. These plug plants were the most suitable for transplantation compared to those grown in other plug trays (45 and 70 mL/cell). When ‘Benihoppe’ plants raised in plug trays for 20, 30 and 40 days were transplanted on the same day, the 20-day-old plug plants showed a better rooting and initial growth 20 days after transplanting compared to those of the older plug plants. The fruit yields of terminal inflorescence were also high in 20-day-old plug plants. Furthermore, in all 3 cultivars, the flower bud emergence of terminal inflorescence tended to be delayed if a certain amount of nitrate nitrogen was present in the soil before fertilization, resulting in decrease in fruit yield until March. The optimal nitrate nitrogen content (mg per 100 g dry soil) before fertilization was 2.5 to 6.3 in ‘Akihime’ and 4.4 to 8.8 in ‘Tochiotome’ and ‘Benihoppe’.
We analyzed the effects of air temperature rises on dormancy period and flowering period of Japanese pear ‘Kosui’ at three locations (Chiba City, Ichikawa City and Ichinomiya Town) in Chiba prefecture. At these three locations, air temperatures tended to rise at a rate of 0.041–0.068°C per year between 1980 and 2009. The dates of full bloom at Chiba City and Ichikawa City have become earlier at a rate of 0.32–0.36 days per year. At Ichinomiya Town, the dates of full bloom did not change after 1992, although it became earlier until 1991. The dates for breaking of endodormancy at Ichikawa City and Ichinomiya Town tended to be delayed at a rate of 0.42–0.52 days per year, due to decreases in effective chilling exposure caused by air temperature rises. The duration of the ecodormancy stage was shortened at a rate of 0.49–0.78 days per year, due to air temperature rises from February to April. It was demonstrated that the model developed by Sugiura and Honjo (1997) can be adopted by Chiba City and Ichikawa City to predict the date of full bloom in the near future, but is not available to Ichinomiya Town, which has a warmer climate. In Ichinomiya Town, the breaking of endodormancy may become incomplete as air temperature rises by 0.59°C in the future.
Effects of sowing time and pinching node positions on the growth and flowering of snapdragons (Antirrhinum majus L.) in the warm temperature zone in Japan were investigated. Snapdragon cultivars, ‘Maryland Pink’, ‘Light Pink Butterfly II’ and ‘Potomac Early White’ were sown on July 16, July 31 and August 14, pinched just above the second or third nodes, and grown under greenhouse conditions where the night temperature was kept above 11C in the winter. When ‘Maryland Pink’ was sown on July 31 or August 14 and pinched at the third nodes, the number of cut flowers and the length of primary lateral shoots from the third nodes increased. Regardless of sowing time, pinching at the second nodes was suitable for ‘Light Pink Butterfly II’ with the increased length of primary lateral shoots from the second nodes. For ‘Potomac Early White’, sowing on July 16 with pinching at the second or third nodes and sowing on July 31 with pinching at the third node were suitable and increased the number of cut flowers in the winter season.
Effects of basal stem heating on yield and fruit quality were investigated as a method of lowering the costs of air-heating in forcing culture of eggplant. Basal stem heating with an electric heating wire resulted in acceleration of lateral shoot and fruit growth and an increase in marketable fruit rates from January to June. The number of fruits and marketable yields in basal stem heating were larger than those in control. Marketable yield from plants with basal stem heating under 10°C air temperature was similar to those from control plants under 12°C air temperature, indicating that basal stem heating can lower the costs of air-heating during forcing culture of eggplant.
To determine the characteristics of carbohydrate competition, we investigated changes in 13C concentration and distribution rate in fruit-bearing branches of Japanese Apricot (Prunus mume Sieb. et Zucc.) ‘Nanko’ during fruit growth. We also investigated the effect of heavy crop load on 13C concentration and distribution rate in each organ of the whole tree and on the growth of the tree. In fruit-growth stage I, the 13C concentration and distribution rate in shoots were higher than those in fruits, however, fruits comprised about 30% of the 13C distribution rate. These findings indicated that the carbohydrate competition between fruits and shoots exists from the early fruit growth stage. The 13C concentration and distribution rate in fruits was the highest in all organs during stage II. Especially, the 13C concentrations in the stone and kernel of the fruit showed significantly higher values. During this stage, the carbohydrate distribution rate in fruit was about 60% and higher than that in shoots at about 40%. In fruit-growth stage III, the 13C concentration in fruit declined in comparison in that in stage II; however, the 13C distribution rate remained about 40%. The 13C concentration in shoots and roots of trees with a heavy fruit load were lower than those of trees with a normal fruit load, and the carbohydrate distribution rates in the former were also lower than those of the latter. A tree with a heavy fruit load showed leaf rolling and etiolation, earlier defoliation, restraint of emerging vigorous shoots, and an increase in dead twigs. In conclusion, it was clear that the carbohydrate competition between shoots and fruit is most significant during fruit-growth stage II. It was thought that trees grown with a heavy fruit load become weaker due to restraint of carbohydrate translocation to shoots and roots.
A simplified method of measuring the tree vigor of ‘Fuji’ apple tree grafted on JM7 dwarfing rootstock was investigated. The number of leaves of the terminal shoot (NL) at the beginning of July positively correlated with length of the terminal shoot, which is commonly used for estimating tree vigor. Therefore, since NL can be easily counted without special equipment, it is considered available in the field as a new index representing tree vigor. Moreover, NL showed a positive correlation with fruit weight per fruit at harvest time. By counting NL at the beginning of July, it is possible to estimate the final fruit weight at harvest.
We investigated changes in the sugar contents of leaves, pedicels, and fruits, and in the photosynthetic rates and translocation of photosynthate in ‘Haruka’ apple trees, along with the effects of bagging on these characteristics. After July, the total sugar contents were higher in ‘Haruka’ than in ‘Fuji’ fruits. ‘Haruka’ demonstrated higher fructose and sucrose contents in fruits than ‘Fuji’ did. ‘Haruka’ those of leaves showed higher total sugar and sorbitol contents compared to ‘Fuji’ in August and September. Total sugar and sorbitol contents in pedicels were also higher in ‘Haruka’ than in ‘Fuji’ during the fruit growing period. The total sugar contents became lower in ‘Haruka’ harvested fruits only when bagged. Decreased fructose contents were responsible for decreased sugar contents in bagged ‘Haruka’ fruits. For ‘Haruka’ and ‘Fuji’, total sugar contents in leaves were not affected by bagging, but the fructose contents in pedicels were higher in bagged fruits than in non-bagged fruits. However, we could not clarify the relationship between the effects of cultivar and bagging on sugar accumulation and photosynthetic rates and the translocation of photosynthate from leaves to fruits.
We examined the influence of girdling on freezing injury of ‘Masui Dauphine’ fig (Ficus carica L.). Freezing injury was observed in cuttings planted in the field at the bud breaking stage. Injury was alleviated in the cuttings with girdling during the previous autumn due to delayed bud breaking. In addition, when the girdling-treated scion was separated into three portions: top, intermediate and basal (according to the growing order) with each having 2–3 buds, the cuttings in the basal portion were less susceptible to freezing injury than cuttings from the top and intermediate portions. The buds in the potted-cuttings could not survive at less than −3°C after low temperature treatment at the bud breaking stage. However, buds from the potted-cuttings with girdling during the previous autumn recorded less freezing injury and showed increased sugar and starch contents. There was also delayed bud breaking in potted-cuttings with girdling. Higher sugar and starch contents and less freezing injury during the cold season were observed in the scion from field-grown young fig trees with girdling during the previous autumn compared to that without girdling. Thus, it is suggested that girdling can ameliorate freezing injury both during the cold season and at the bud breaking stage by enhancing the reserve nutrients in dormant branches and delaying the date of bud breaking.
The phytopathogen Ralstonia solanacearum undergoes spontaneous phenotype conversion (PC) from a wild-type pathogenic form to a non-pathogenic form in plants, soil, broth culture, and after prolonged culture on agar plates. We investigated the suppression of bacterial wilt disease of eggplant using a PC mutant (E-PCstr). We also tested varietal differences in suppression of bacterial wilt disease by E-PCstr using 12 susceptible commercial eggplant cultivars. At primary inoculation, eggplant seedlings were inoculated with 20 mL cell suspensions (106, 108 cfu·mL−1 of live and heat-killed E-PCstr). Seven days after primary inoculation, the seedlings were challenge inoculated with 20 mL of bacterial suspension (107 cfu·mL−1 of the pathogenic strain 8238rif which is a spontaneous mutant from the wild type strain 8238 and resistant to rifampicin). In seedlings inoculated with 108 cfu·mL−1 of live E-PCstr, effective suppression of bacterial wilt disease was observed. In the suppressed seedlings, E-PCstr colonized and vertical movement of 8238rif was limited. There were varietal differences in suppression of the bacterial wilt disease induced by E-PCstr, and a correlation between the suppression of and resistance to bacterial wilt disease was observed among the eggplant cultivars.