In greenhouses heated from early December (plot A) and early Jannuary (plot B), and in an open field (plot C), early ripening satsuma mandarin ‘Miyagawa Wase’ and ‘Okitsu Wase’ trees were densely planted in sub plots in combination with organic substance application (1.5 t/10 a/year of rice straw and twice as much rice straw as normal) and fertilizer application (N: 27, P2O5: 24, K2O: 22 kg/10 a/year and 1.5 times the recommended rate). Yields and factors which affect the yield fluctuation were analyzed by employing data from 3 years old, the following year of planting, to 12 years old. There was no significant difference in the yield, leaf area index (LAI), flower-bud count, and other various parameters between organic substance treatments or between fertilizer treatments. Though plot A showed an appreciable yield fluctuation and reduction in yield due to removing filler trees, this cultivation system showed a greater potential yield compared to plot B. LAI in ‘Okitsu Wase’ was larger than that in ‘Miyagawa Wase’ until the filler trees were removed, so the initial yields of the former tended to be slightly higher. Relationships between some factors vs. yield per unit land area were determined. The results clearly indicated that LAI was the strongest factor affecting yield in different growing conditions (plots A, B, and C) and cultivars (‘Miyagawa Wase’, ‘Okitsu Wase’). The trees growing in the greenhouse heated from early December (plot A) had a small number of flower buds, but they represented high fruit set percentages and showed a comparatively strong correlation between the number of flower buds and yield.
Seabuckthorn (Hippophae rhamnoides L.) is a small fruit tree belonging to the family Elaeagnaceae. Because seabuckthorn fruit is rich in unsaturated fatty acids and vitamins, this plant has potential as a food and medicinal crop. Here, we focused on symbiotic nitrogen fixation that could aid in the cultivation of this species. Microscopic observations showed that seabuckthorn root nodules have a standard morphology characteristic of Frankia-actinorhizal root nodules. Under nitrogen-free conditions, seabuckthorn seedlings inoculated with a homogenate of root nodules grew normally, and the fresh weight of root nodules was positively correlated with plant growth. In the field, nitrogenase activity in root nodules was high from May to September, when air temperatures were high and photosynthesis was active. Inhibition of nitrogen fixation by nitrate has been well documented in the root nodules of legumes. Therefore, we investigated the effect of nitrate on nitrogenase activity in seabuckthorn root nodules. Nitrogenase activity in seabuckthorn root nodules was not inhibited by the addition of high concentrations (up to 30 mM) of nitrate over a short term (5 days), but was apparently inhibited by long-term (20–30 days) treatments with 5 and 10 mM of nitrate.
The primary objective of this study was to characterize the effects of calcium chloride spray on the formation of stone cells and peroxidase activity in ‘Niitaka’ pear fruit. Calcium chloride (0, 0.3, 0.5, and 1.0%) was sprayed 4 times on selected 15-year-old ‘Niitaka’ pear trees at 10-day intervals with a handgun until runoff, beginning 20 days after full bloom (DAFB). The calcium content and peroxidase activity were determined in flesh extracted from harvested fruit. The distribution of stone cells in the fruit flesh was determined via light microscopy, using phloroglucinol dye. The calcium contents of the leaves and fruit increased significantly in the fruit sprayed with 0.5 and 1% CaCl2, as compared to the control, or the fruit sprayed with 0.3% CaCl2. The stone cell contents in the fruit flesh decreased significantly when the fruit were sprayed with 0.5 and 1.0% CaCl2. Fruit treated with calcium chloride showed an increase in the rate of small stone cell cluster formation (< 200 μm2), whereas the rate at which medium (200–400 μm2) and large (400 μm2 <) clusters formed was significantly reduced. Peroxidase activity in the fruit flesh increased substantially at 60 DAFB, and decreased with fruit development. Peroxidase activity was much higher in the non-treated fruit than in those treated with 0.5% CaCl2. The activities of bound and soluble peroxidase in the cell wall were lower in the fruit treated with 0.5% CaCl2 than in the non-treated fruit. In our experiment, the stone cell content and stone cell size decreased significantly in fruit treated with calcium chloride, as the result of a reduction in lignification due to low peroxidase activity (soluble and bound).
The chromosomes of trifoliate orange (Poncirus trifoliata (L.) Raf.) were stained with chromomycin A3 (CMA) and double stained with alkylating fluorochromes 4′-6-diamidino-2-phenylindole (DAPI) and propidium iodide (PI). PI-positive (PI (+)) regions in PI/DAPI staining were identical to CMA-positive (CMA (+)) regions. The signals of PI (+) were more stable than those of CMA (+). Based on the relative-sized PI (+) signals and the morphology of no-signal chromosomes, eighteen chromosomes of trifoliate orange were classified into 9 groups. Genomic in situ hybridization (GISH) was performed on trifoliate orange chromosomes using the double probe of DNA from trifoliate orange labeled with digoxigenin-rhodamine (red), and from ‘Nankan No. 20’ satsuma mandarin (Citrus unshiu Marcow.) or ‘Tosa Buntan’ pummelo (C. maxima (Burm.) Merr.) labeled with biotin-FITC (green). Sixteen GISH signals with a higher intensity were detected in the identical positions of PI (+) regions. The coloration of GISH showed 13 yellow signals and 1 green signal by the biotin probes of satsuma mandarin, and 5 yellow signals and 11 red signals by those of ‘Tosa Buntan’ pummelo. This indicates that trifoliate orange is more closely related to satsuma mandarin than ‘Tosa Buntan’ pummelo, because red signals indicate that they share no homologous sequences between genomes. GISH signals on the secondary constriction regions of all B-type chromosomes and on the telomeric region of the D4-type chromosome were yellow or green in both satsuma mandarin and ‘Tosa Buntan’ pummelo biotin probes. This result suggests that these regions in trifoliate orange chromosomes can be homologous to satsuma mandarin and ‘Tosa Buntan’ pummelo genomes, and are thus conserved regions.
In various plant species, polyamines have been implicated in regulating developmental phenomena as well as responses to environmental stimuli. The role of polyamines in regulating developmental phenomena in olive trees, such as flowering, is poorly understood, although seasonal changes and temperature effects on polyamine levels in olive trees have been reported. In this study, levels of free polyamines (putrescine, spermine, and spermidine) in the leaves of trees kept under non-inducing conditions were compared with polyamine levels in trees that were induced to flower under chilling and non-chilling conditions. Putrescine and spermine levels were much higher in leaves kept under inductive chilling conditions compared to control trees kept vegetative, but such increased levels of polyamines did not occur in trees that were induced to flower under non-chilling conditions. These results clearly differentiated between the effects of temperature versus the effect of developmental change on free polyamine levels in olive leaves. The results show that changes in free polyamine levels in leaves have little relevance to flowering in olives. Free polyamine levels within auxiliary buds increased when vegetative buds transformed into flowering buds and then declined when buds developed into flowers. Compared to floral buds, immature and mature fruits contained much smaller amounts of polyamines.
Japanese pear (Pyrus pyrifolia) and quince (Cydonia oblonga) form different inflorescence architectures, the former forms raceme inflorescence with about eight flowers and the latter forms solitary-flowered inflorescence. We observed the floral differentiation of Japanese pear and quince to clarify the differences in their early inflorescence development. Floral differentiation of Japanese pear occurred in late June. After apical meristem turned to a dome-like structure, inflorescence developed by forming lateral flower meristems in axils of bracts. The apex of inflorescence became the terminal flower meristem, two or three meristems were initiated in axils of outer bracts and leaf primordia, and finally approximately eight flower meristems were formed in the inflorescence. Floral differentiation of quince was initiated from late October to November after eight leaf primordia had been initiated. Apical meristem transformed to a dome-like structure and initiated sepal primordia. Axillary meristems of bracts or leaf primordia in Japanese pear differentiate to flower meristem while those in quince remained undifferentiated to form axillary buds in the following growing season, resulting in an inflorescence architecture difference in Japanese pear and quince.
We investigated the effects of supplying warmed water to the graft union of tomato and eggplant grafted cuttings during low-air-temperature storage on graft development and plant growth after storage. The scions of grafted cuttings were held at an air temperature of 9 to 12°C, while the region from the cut end of the rootstock cuttings to the graft union was held at 12 to 37°C in water during 4 days’ storage. The tensile strength of some cuttings’ graft union was measured as an index of graft development. The tensile strength of the tomato graft union was much improved when the graft union temperature ranged from 23 to 27°C. That of the eggplant graft union increased as the temperature rose up to 29°C. After 4 days’ storage, the remaining cuttings were planted in vermiculite medium and grown in a growth chamber. Cuttings from the temperatures that gave a higher tensile strength tended to grow larger. We also investigated the effects of supplying the water at 28°C to the graft union on the storage quality of cuttings by measuring the water status, gas exchange, and chlorophyll fluorescence parameters after 4 days’ storage at an air temperature of 9 to 11°C. The leaf water potential and leaf conductance of scions with warmed graft unions were significantly higher than those with unwarmed graft unions. The chlorophyll fluorescence parameters ΦPSII and the electron transfer rate were maintained with warmed water during storage, but were significantly decreased without warmed water application. These results indicate that keeping the graft union warm during low-air-temperature storage can improve graft development, storage quality, and plant growth after storage.
Effects of bahiagrass (Paspalum notatum Flügge.) intercropping and arbuscular mycorrhizal fungi (AMF), Gigaspora margarita Becker and Hall, on the growth and activities of anti-oxidative enzymes (superoxide dismutase (SOD) and catalase (CAT)) in radish (Raphanus sativus L. ‘Midoribijin’), a non-host plant, was studied. Radish was grown with and without bahiagrass in a root box system divided into 5 compartments which allows AMF hyphae, but not roots, to enter between compartments. Pots without AMF inoculation were prepared as a control. G. margarita by itself had no significant effect on radish growth. Radish roots were colonized by G. margarita only when intercropped with bahiagrass; however, no arbuscule was observed and a lot of new spores were found on the radish root. Protein contents of radish roots were increased, but the plant biomass of radish, and the activities of SOD and CAT of roots were significantly decreased by AMF root colonization. These results suggest that the unavoidable invasion of hyphae into non-host plant roots due to intercropping with host plants, such as bahiagrass, that strongly promote AMF growth would result in the decline of non-host plants.
The effect of seed tuber (ST) weight on the development of main shoots, aerial tubers (bulbils, AT), new tubers (below ground, NT), and flowering spikes (inflorescences) was examined in Japanese yam plants (Dioscorea japonica) grown under different photoperiods and with plant growth regulators (PGRs). Within the same PGR and ST-weight group, the main shoot lengths of plants grown under a 24-h photoperiod (constant light, LD) were found to be longer than those grown under an 8-h photoperiod (SD) in all seasons. Furthermore, within the same photoperiod and ST-weight group, except for the plants grown from 25 g of ST (25gST plants) under SD conditions, the main shoot lengths of control and gibberellic acid (GA3)-treated plants were found to be longer than those of uniconazole-P (Uni)-treated plants. These tendencies were stronger in the 50gST plants than in the 25gST plants. In the 25gST plants, the final fresh weight (FW) of NT and the combined FW of AT and NT were greater in plants grown under LD conditions (LD plants) than those of SD plants; however, this was not observed in the case of the 50gST plants. This is because AT and NT development commenced earlier in the 25gST plants than in the 50gST plants. Furthermore, in the case of the 25gST-LD plants, the control plants also produced a few AT. Hence, we could confirm that the yield of NT was slightly increased by the inhibition of AT in the GA3-treated plants. The 25gST or 50gST-SD plants had only one peak of spike development from June through July, whereas the 25gST or 50gST-LD plants had two peaks of spike development, that is, in June and July and then again from September through October. In the season (June to July) of early spike development, the number of spikes per LD plant was greater than that in the SD plants, and the total number of spikes per plant was inhibited by GA3 treatment. These tendencies were stronger in the 50gST plants than in the 25gST plants.
Postharvest modification of flesh firmness and its relationship to pectin solubility were investigated in eight commercial cultivars of muskmelon (Cucumis melo L. var. reticulatus Naud.). A considerable difference in the softening rate was found between cultivars. Relatively rapid softening to desirable texture was found in the flesh of ‘Sapporo King ER’, ‘Melorin’, and ‘King Melty’ within three or four days after harvest. The flesh of ‘Ichihime’, ‘Red 113’, and ‘G 08’ showed slower softening, taking approximately a week to obtain acceptable texture. Especially in ‘Ichihime’ and ‘Red 113’, the flesh remained relatively firm even after 14 days. ‘Rupia Red’ and ‘Earl’s Knight Shunjukei’ showed an intermediate softening rate. These characteristics corresponded to the objective measurement, and a logarithmic relationship was found between sensory scores of flesh firmness and hardness measured by texture analyzer. Furthermore, significant differences between cultivars in the rate of pectin solubilization were observed, which corresponded to the rates of flesh softening. A significant negative correlation was observed between texture analyzer-measured hardness and water-soluble pectin content, which seemed to fit an exponential curve. The hardness for acceptable eating quality varied from cultivar to cultivar. The contribution of this objective method of measuring flesh firmness to the evaluation of eating quality, and its difficulty due to differences in postharvest behavior of cultivars, are discussed.
Embryological characters during microsporogenesis, megasporogenesis, and the development of male and female gametophytes in Eustoma grandiflorum were observed by microscopy. The results are as follows. 1. The formation of anther walls was of the dicotyledonous type. The tapetum was of the heteromorphic and glandular type. Tapetal cells on the connective side elongated radially. 2. Cytokinesis in microsporocyte meiosis was of the simultaneous type and microspore tetrads were tetrahedral. 3. Mature pollen grains were 2-celled and had 3 germ furrows. 4. The ovary was bicarpellary syncarpous and unilocular, having parietal placentas. Ovules were numerous and anatropous. 5. The archespore under the nucellar epidermis directly developed a megaspore mother cell, which in turn underwent meiotic division to form 4 megaspores arranged in a line or T-shape. The chalazal megaspore was observed to be functional. 6. The formation of the embryo sac was of the polygonum type. Before fertilization, the 2 polar nuclei fused into a secondary nucleus. The mature embryo sac was made up of 7 cells. 7. It was found at a very low rate that there were 2 megasporocytes or 2 embryo sacs in an ovule.
We analyzed the petals of orange- and yellow-flowered cultivars of 9 Compositae (Asteraceae) species for total anthocyanin content, total carotenoid content, and carotenoid composition to clarify the mechanisms responsible for the differences in color. Petals of both orange- and yellow-flowered cultivars of these species contained yellowish carotenoids in common. There were three different ways for orange-flowered cultivars to add redness to the yellow base in order to form orange petals. The first way to display orange is to accumulate more anthocyanins than yellow-flowered cultivars; orange petals of Chrysanthemum morifolium, Gerbera jamesonii, and Zinnia elegans are mainly formed in this way. The second is to accumulate more carotenoids than yellow-flowered cultivars; orange petals of Helianthus annuus, Tagetes erecta, and Tagetes petula are formed in this way. The third is to accumulate more reddish carotenois than yellow-flowered cultivars; orange petals of Calendula officinalis, Gazania spp., and Osteospermum ecklonis are mainly formed in this way. These three ways could be combined through inbreeding to produce orange flowers that vary in color tones.
Sweetpotato roots were stored under a continuous flow of 0% or 1% O2 (balance N2) or air for 7 days at 20°C to study the effects of short-term exposure to low O2 on their physiological responses and quality. During the course of the experiment, no visible signs of injury or decay were observed. However, low O2 treatments increased the soluble solid content and weak off-odors were detected by olfactory evaluation in roots stored at 0% O2. The intensity of off-odors increased as the concentrations of acetaldehyde and ethanol increased in roots during storage. Ethanol concentrations were higher than those of acetaldehyde, which remained low during storage in 1% O2 and air, but increased greatly in roots stored at 0% O2. Pyruvate decarboxylase (PDC) activities in roots exposed to 0% or 1% O2 increased by 3.1- and 2-fold respectively over levels in roots stored in air by day 7. Alcohol dehydrogenase (ADH) activities in roots exposed to 0% or 1% O2 increased by 1.6- and 1.7-fold respectively over levels in roots stored in air by day 7. ADH-specific activity was about 10-times that of PDC. The pH of root homogenate exposed to air remained constant, whereas the pH increased and decreased, respectively, in roots stored at 0% or 1% O2. PDC showed stability over the pH range 5.5–7.0, whereas ADH exhibited stability over the pH range 6.0–7.5. The Km of PDC in sweetpotato was 0.56 mM for pyruvate, whereas the Km of ADH was 0.19 mM for acetaldehyde. From these results, there may be some potential for the short-term exposure of sweetpotato roots to low O2 in place of low temperature treatment to prolong shelf-life, although ethanol fermentation may be accelerated under low O2 atmospheres.