The role of UV radiation in the accumulation of anthocyanin in 'Gros Colman' (Vitis vinifera L.), a light-sensitive cultivar, was examined by using berry sections prepared from the softened green berries at veraison. The sections were exposed to diffuse sunlight under covering materials such as glass plate, polyolefin film (PO), poly vinyl chloride film (PVC), UV-proof PVC, ethylenetetrafluoroethylene (ETFE), polycarbonate resin plate (PC), fiber-reinforced acrylic resin plate (FRA) for 72 hr. The accumulation of anthocyanin in the berry skins under diffuse sunlight was greatly reduced with the covering materials which prevent the penetration of UV light. Artificial irradiation with an UV lamp (peak wavelength: 352 nm) greatly promoted the accumulation of anthocyanin. With increasing light intensity in the UV-A region (320-400 nm) up to 0.4 W·m-2, the anthocyanin content markedly increased, reached a plateau and then levelled off at 2.3 W·m-2. Increasing the intensity of white light up to 8.5 W·m-2 induced a gradual accumulation of anthocyanin. When UV irradiation was combined with white light at about 4.1 W·m-2, the accumulation of anthocyanin was further enhanced. These results suggest that UV light is involved in the accumulation of anthocyanin in 'Gros Colman' grapes. Hence, UV permeability of covering materials in the protected culture should be considered.
A differential display technique that uses an arbitrary sequence primer, labeled with digoxigenin, was applied to detect differentially expressed mRNAs relating to citrus rind injury under various storage conditions. mRNAs were isolated and identified, some of which share a high similarity with those detected in plant organs by a virus infection, elicitor treatments, or water-stress, whereas others share homology with auxin-inducible genes. Expressions of three genes were analyzed by a reverse transcriptase-polymerase chain reaction (RT-PCR) in the rind of 'Kiyomi' tangor (Citrus unshiu Marc. × C. sinensis Osb.). The three genes were induced early under conditions that favored severe rind injury after a lengthy storage. Differential expressions of those genes should be useful to identify unfavorable storage conditions for citrus fruit.
Responsiveness of three New Zealand northern highbush blueberry cultivars (Vaccinlum corymbosum L.), 'Nui', 'Puru' and 'Reka' to three degrees of regulated nutrient availability was examined: 1) in the control treatment, no nutrient was added, 2) in the solid fertilizer treatment, a standard commercial fertilizer was applied at the start of the experiment, the release of nutrients being dependent on the properties of the fertilizer and environmental conditions, and 3) in the fertigation treatment, a dilute solution of readily available nutrients was supplied daily. Treatments were applied from mid-May 2001 up until plants were destructively harvested in mid-September 2001. For all three cultivars, accumulated dry matter in the fertigation treatment was 2 to 3 times that in the solid fertilizer treatment, whereas that in the control treatment was the least. 'Nui' had the lowest total dry matter levels, they were significantly higher in the fertigation treatment though because of increases in aboveground growth. The root system was unresponsive to the varying nutrient levels applied. 'Reka', the fastest, growing cultivar, had the most responsive root system, its dry weight increasing 2.9 fold in the fertigation compared to the solid fertilizer treatment, that of 'Puru' was intermediate. We concluded that there is potential to apply a finely regulated fertigation system to commercial blueberry production.
To prevent bolting and to develop a new cropping system for harvest in June, the effects of tunnel covering and a 16-hr photoperiod (LD) on the growth, flower initiation and bolting of Japanese bunching onion (Allium fistulosum L.) cultivars 'Kincho', 'Asagi-kujo' and 'Cho-etsu' were investigated. The maximum air temperature was 20 - 25°C higher under the tunnel than in the open field. Growth during the treatments was accelerated by tunnel covering and LD, solely or combined. With 'Cho-etsu', tunnel covering alone effectively prevented bolting, because devernalization was induced by a high day temperature, but with 'Kincho' and'Asagi-kujo', it did not; but when it was combined with LD, the bolting rate was decreased to 7-24%. The inhibitory effect of LD alone on the bolting rate was not observed for 'Kincho' and 'Asagi-kujo'. However, with 'Cho-etsu', LD alone sufficiently prevented bolting; when combined, LD and tunnel covering prevented bolting completely. These results indicate that the 16-hr photoperiod induced devernalization of Japanese bunching onion. The possibility of harvesting some mid-season varieties, such as 'Kincho' and 'Asagi-kujo' in June was successfully established. As the bolting rate did not correspond to the developmental stage of flower buds during the treatments in 'Asagi-kujo', abortion of developing flower buds may be induced by high day temperature.
Lettuce plants were grown in naturally-lit glasshouses maintained at either 25/20°C or 20/15°C to elucidate the relationship between stem elongation and flower initiation. The first sign of inflorescence initiation, i.e., dome-shaped apices, could be detected 28 days after sowing (DAS) at 25/20°C and 39 DAS at 20/15°C. Plants went into the bolting stage without head formation at 25/2°C, but plants exhibited head formation at 20/15°C. Stems elongated exponentially with time, irrespective of temperatures. Log-linear relationships could be found between stem length and diameter until the first sign of inflorescence initiation, but thereafter the relationships deviated from linearity at both temperatures. The allometric exponents for the vegetative shoots were close to unity at both temperatures. Likewise, log-linear relationships were found between stem length and stem dry mass and between stem dry mass and leaf dry mass until the first sign of inflorescence initiation. These results show that vegetative shoots can be discerned from flower stalks by their shapes independent of whether the plants formed heads or not.
The effect of ABA on thermostability of the photosynthetic apparatus in leaves of cucumber (Cucumis sativus L.) was investigated. Cucumber plants grown in soil at 25°C (day and night) were administered foliar sprays of 1 mM ABA when the third leaves were fully expanded. Compared to untreated control leaves, ABA-treated leaves had faster rates of photosynthetic O2 evolution and a higher photosystem (PS) II chlorophyll fluorescence yield following exposure to 45°C in the dark for 10 min. These effects of ABA were attenuated over time after ABA treatment. Heating the isolated thylakoids from treated and control leaves at 40 °C in the dark for 5 min revealed that heat-induced loss of PS II- and PS I-mediated electron transport rates was alleviated by the ABA treatment. The PS II reaction center was not heat-damaged, regardless of the source of thylakoids. On the other hand, a reduction in the loss of proteins and manganese during heat treatment occurred in thylakoids from ABA-treated leaves compared to those from control leaves. This reduction indicates that ABA increased the thermostability of the O2 evolving complex. Direct treatment of isolated thylakoids with ABA was ineffective in preventing the heat inactivation of the photosystems. Thus, it seems that high foliar levels of ABA induce a mechanism associated with thermostability of the O2 evolving complex. However, these effects of ABA on isolated thylakoids were smaller than were those on intact leaves, indicating that ABA can also induce thermostability in other components of the photosynthetic apparatus besides the O2 evolving complex.
Abscission of sepals from cut delphinium flowers is prevented by treatment with silver thiosulphate (STS). However, the sepals still wilt and the pistils develop which reduce flower quality. To understand the process of wilting, unrelated to that initiated by ethylene, sugar uptake and metabolism in cut delphinium flowers were examined. STS-treated delphinium sepals wilted 4 to 9 days after harvest accompanied by a decrease in fresh weight while the pistils continued to grow. A decrease in water content with a simultaneous reduction in soluble carbohydrate content suggested that wilting is attributable to a decrease in soluble carbohydrates as the osmoticum. The activities of cell wall and soluble acid invertase, sucrose synthase (SS), and mannitol dehydrogenase (MDH) were measured because these enzymes are related to sink mechanism in sucrose- and mannitol-translocating plants. Cell wall invertase activity and p-chloromercuri-benzenesulfonic acid (PCMBS)-sensitive sucrose uptake by the sepals decreased to a very low level during wilting. When intact florets were supplied with 14C-sucrose, a change in sucrose distribution in sepals corresponded with that in cell wall invertase. Therefore, the reduction in cell wall invertase activity that decreases the soluble carbohydrates as osmoticum could be related to sepal wilting. SS activity that is known to be important in sink metabolism also decreased during sepal wilting, suggesting that SS was related to the wilting. MDH activity in pistils paralleled their rapid growth while cell wall invertase and SS activities remained consistently high except at harvest.
The rooting ability of cuttings of current shoots from trifoliate orange (Poncirus trifollata [L.] Raf.) trees at various ages was determined. All cuttings were collected in early June 2001. Rooting abilities varied among various ages of trifoliate orange trees. Forty-five days after cutting, the current shoots from one- and two-year-old trees had 100% rooting; those from 15- and 25-year-old trees had 0%. From three-year-old to five-year-old trees, the rooting percentage decreased as the age increased. The number of roots produced correlated positively with the rooting percentage. In another experiment, scions from current shoots from mature 'Aoshima' satsuma mandarin (Citrus unshiu Marc.) were grafted onto two-year-old trifoliate orange seedlings. All trifoliate orange portions of cuttings grafted with 'Aoshima' satsuma mandarin scions rooted.
The effect of post-planting temperatures on root elongation of precooled bulbs from 13 tulip cultivars that were grown hydroponically was studied. Root dry weights and optimal temperatures for root elongation differed greatly among cultivars. A similar response was obtained in both water and pumice cultures. Our results indicate that success for early forcing depends on using suitable cultivars, according to the soil temperature available at the time of planting.
The effects of 0, 50, 150, 250 and 500 mM NaCl for a short duration on the accumulation of Na, Cl and proline betaine in the roots, stems and leaves of young Poncirus trifoliata seedlings were investigated. The degradation of nuclei in the cells of the apical meristem of the root was observed by fluorescence microscopy after the nuclei were stained with 4'-6-dlamidino-2-phenylindole (DAPI). With increasing concentrations of NaCl, the Na and Cl content in the leaves, stems and roots increased while tree growth was reduced proportionately. The leaves accumulated more Na and Cl than did the roots, resulting in severe injuries, more so in the former than in the latter, with increasing NaCl concentrations. Proline betaine accumulated in the roots at 250 and 500 mM NaCl, but it did not increase in the leaves at any treatment. Salt stress also induced several anatomical changes in the apical meristem from the root tip to 2-3 mm, such as vacuolation in the cortical cells, abscission of root cap cells, and nuclear degradation.
The effects of high temperature treatment by non-ventilation of greenhouse on fruit yield and the incidence of diseases and insects in summer cucumber production were evaluated against constant ventilation (control). Fruit yield for 5 cultivars of summer cucumber was increased by setting the ventilation temperature at 45°C from 4:30 until 10:30. Diseases and insects were effectively suppressed by high temperature. Non-ventilation should be done during the lunch break during 11:30-13:20 in consideration of the worker's comfort. Most diseases and insects (except mites) could be controlled. However, with daily high-temperature treatment the number of dead or malformed fruits increased. Until the beginning of harvest, frequent non-ventilation treatment may exterminate diseases and insects and increase the number of fruiting nodes. Thereafter, frequency of the treatment should be reduced to ensure fruit set and growth.
The resistant F1 progenies of strawberry (Fragarla × ananassa Duch.) that were inoculated with anthracnose during the young seedling stage were compared with non-inoculated seedlings for fruit quality and earliness. The progenies were derived from the cross between susceptible 'Nyoho' and resistant 'Hokowase'. The inoculated and non-inoculated seedlings had similar mean values and variations in the fresh weight and firmness of fruits, Brix values, acidity, soluble solid/acid ratios, color of fruit juice, L*, a* and b* values of fruit skin color, and a similar distribution in the dates of flower-bud emergence. The results indicate that there are no correlations between resistance to anthracnose and a) traits of fruit quality and b) earliness of strawberry. Thus, screening for anthracnose resistance in the young seedlings may not lead to discarding germplasm with high fruit quality and an early flowering trait.
Bulbing response of Allium × wakegi Araki cv. Kiharabansei No.1 to temperature prior to bulb formation was investigated. The plants exposed to 5°C for 35 days were grown at 20°C under photoperiods ranging from 11 to 14 hrs. The control plants were kept above 15°C before the photoperiodic treatment. Regardless of the exposure to low temperature, the plants did not form bulbs under 11- and 12-hr photoperiods, whereas they did under a 14-hr photoperiod. Under 13- and 14-hr photoperiods, the plants exposed to low temperature had higher bulbing ratios (the maximum diameter of basal leaf sheath/the minimum neck diameter) and higher percentages of tillers with bulb scales (bladeless swollen leaves) than had the control plants. Low temperature exposure did not induce bulb formation of A. × wakegi, but shortened the critical photoperiod for bulb formation from 14 hrs to 13 hrs. When bulbs were stored between 1 and 25°C for 50 days and grown at 20°C under a 13-hr photoperiod, storage at or below 15°C promoted the formation of new bulbs. Storage at 10°C was more effective than that at 15°C, but below 10°C, it exerted no additional effect. When bulbs were stored at 5°C between 0 and 84 days and grown at 20°C under a 13-hr photoperiod, the formation of new bulbs was promoted as the cold storage period was extended. The promotive effect of low temperature on bulb formation was weakened by subsequent exposure to 25-35°C.
A method to remove astringency and yet retard fruit softening during storage in early ripening Japanese persimmon 'Tonewase' grown in a plastic greenhouse was developed. This method which involved treatment of fruits for 10 hr at 35°C with a mixture of 50% CO2 and 1-1.5 ml of ethanol per kg of fresh fruit proved to be more effective to reduce softened fruit than the prevailing treatment using 95-100% CO2 for 16 hr at 25°C. With this new method, ethylene production by the treated fruit peaked at 0.31 μl·kg-1·hr-1 immediately after the end of the treatment and decreased quickly afterwards. This response demonstrates that the burst of ethylene did not stimulate fruit softening at 35°C.