The involvement of ethylene in the pedicel in preharvest fruit drop and the relationship between ethylene in the pedicel and its production in the flesh and the seed were investigated in 'Tsugaru' apple. The induction of pedicel abscission was achieved by the injection of ethylene with a syringe, whereas it was inhibited by 2, 5-norbornadiene (NBD), an antagonist of ethylene action. The injection of ethephon into the fruit core, or the spray on the bourse resulted in increasing ethylene content in the pedicel and subsequent fruit abscission. The treatment with aminoetoxy-vinylglicine (AVG) of the fruit core, the inhibitor of ethylene synthesis, reduced the fruit abscission and ethylene content in the pedicel. Ethylene production of the seed and the flesh, and its content in the pedicel in 'Tsugaru' greatly increased before the rapid increase in fruit drop. Fruit of 'Jonagold' usually do not exhibit preharvest drop, the ethylene production and ethylene content are low; they increased little before harvest. Therefore, ethylene likely originates in the flesh and seeds and is translocated to the pedicel where it acts to induce fruit abscission.
Seven (18%) and 4 (6.2%) individuals from 39 and 65 F2 progenies obtained from the two interspecific FI hybrids between Lactuca saligna L. and L. sativa L. cv. Bronze were found to be spontaneous triploids. The length (mm) and weight (mg) of achenes formed on L. sativa, L.saligna and their F, hybrids were 4.01, 1.04; 2.70, 0.35; and 4.41 mm, 1.33 mg, respectively, and those of achenes obtained from L. saligna × L. sativa was 2.51 mm and 0.29 mg. The size of achenes obtained on the Fj hybrids ranged from 3.3 to 6.2 mm and 0.2 to 2.4 mg. The size of the F2 triploid seeds from the FI hybrids were classified into 2 groups; 5 triploids with small achene (0.7-1.1 mg) and the remaining 6 triploids with even heavier achene than L. sativa (>1.8 mg). The phenotype of 5 isozyme loci studied, Got-l, Pgi-l, Pgi-2, Pdh-1, and Pdh-2, always showed the 4 : 4 : 1 in band intensity in the triploids, which enabled us to analyze the genotypes. When the gene of L. sativa was named 'l' and that of L. saligna, 'g', all triploids were always heterozygous in the 5 isozyme loci, ggl or gll ; this suggests that triploids resulted from a union of a reduced gamete with an unreduced gamete. The triploids from small achenes were ggl in almost all of the five loci, whereas those from the large achenes were gll. Thus, the curious combinations between achene size and the genotypes indicate that the survival rate of individuals with the distorted combination of genes to one of the two parent species is higher than that with the random combination.
Effects of photoperiod on flower bud initiation of eight okra (Abelmoschus esculentus) cultivars were investigated in spring and autumn. The plants received 10 hr of natural day-length in short-day (SD) or natural day-lengths (ND) ranging from 14.16 to 14.29 in the spring and 11.07 to 12.17 in the autumn. To adjust for a 16-hr photoperiod (LD), the ND was extended with fluorescent lights (3μmol·m-2·s-1). Flower buds of 'Clemson Spineless' and 'Emerald' were initiated at the lower node, and they occurred earlier under SD than did those under LD or ND in the spring. Promotive effects of the short-day response in 'Clemson Spineless' and 'Emerald' were not clear in autumn; photoperiodic responses of both cultivars may have been modified by low air temperatures. On the other hand, flower buds of 'Benny', 'Gulliver', 'Natsu no Megumi', 'Star Debut', 'Star Light' and 'Suisei Gokaku' which were initiated at the similar node, occurred simultaneously, regardless of day-length and season. Flower bud initiation of all cultivars continued under short-day in spring and all day-length treatments in autumn. In contrast, a reversion to the vegetative phase occurred not only in 'Clemson Spineless' and 'Emerald' but also in 'Benny', 'Star Debut' and 'Suisei Gokaku' under LD and ND in the spring. Based on these results, 'Clemson Spineless', 'Emerald', 'Benny', 'Star Debut' and 'Suisei Gokaku' are believed to be quantitative short-day plants for flower bud initiation, whereas 'Gulliver', 'Natsu no Megumi' and 'Star Light' are day-neutral.
Somatic hybrid plants were obtained between Arabidopsis thaliana (L.) Heynh. and cabbage (Brassica oleracea L. var. capitata) by protoplast fusion of the parental species under polyethylene glycol (PEG). The hybrids were cultured in modified 8p liquid medium. After the transfer of micro-calli to callus development medium, and the transplanting of calli onto regeneration medium, 12.4% of calli regenerated shoots. Although most of them were regenerants of A. thaliana, two shoots revealed the hybrid characteristics. The two somatic hybrid shoots were propagated and established as hybrid plants. Both plants exhibit hybrid morphological properties, and hybridity for the nuclear triose-phosphate isomerase (Tpi) gene and the mitochondrial genome, but the chloroplast genome of both plants was identical to that of the cabbage. The hybrid plants would be useful both for the breeding of cabbage and academic studies on the function of nuclear and organellar genes of cabbage.
Tomato 'Ohgata-Fukuju'plants were cultured hydroponically in a greenhouse by using deep flow technique (DFT) and nutrient film technique (NFT) systems. Generally, the rate of uptake of all nutrient components except for PO4 increased from the start of flowering until fruit harvest, and thereafter decreased. Fruit weight of a tomato plant having three trusses and the average rate of nutrient uptake (ARU: me-plant-1·week-1) were measured six times after the onset of flowering. The regression formula of fruit weight to the ARU of PO4 was polynomial, whereas that to the ARU of NO3 or K was linear, with a high correlation coefficient (r) 0.91, 0.91 and 0.97, respectively. The ARU of PO4 and NO3 when maximum fruit weight was recorded, ranged from 15-20 and 50-55 me · plant-1·week-1, respectively. Tomato plants were cultured by using a DFT system under a limited supply of NO3 and PO4; the solution was renewed weekly. Fruit weights in relation to the ARU of PO4, NO3 and K were also examined. Fruit weights relative to the ARU of NO3 and PO4 in these experiments were slightly different from that expected from the regression formula mentioned above. However, the fruit weights under a weekly supply of NO3 and PO4 were not significantly different from the maximum fruit weight of tomato cultured in solution with a constant concentration.
A solution of ammonium molybdate (Mo: 1 mM) was infiltrated into floral disks of several flower plants that contain anthocyanin to study the basis of bluing caused by molybdenum. The floral disk colors of Eustoma grandiflorum (Raf.) Shinn. 'Tokinoakari', 'Lination Red' anc Tulipa gesneriana L. 'Purple Flag' became blue when treated with ammonium molybdate Those of Eustoma grandiflorum 'Exrosa Blue' and Iris hollandica hort. 'Blue Magic' became slightly bluish. Molybdenum had no bluing effect on Tulipa gesneriana 'He de France', Rosa spp 'Carienta' and Dianthus caryophyllus L. 'Cain'. The minimum concentrations of molybdenum for bluing of excised flower tissues were 0.5 mM in 'Lination Red' and 1 mM in 'Purple Flag' 01 'Exrosa Blue'. Aluminum had no effect on flower colors at any concentrations. The flowers ol five varieties which showed bluing by molybdenum contained the anthocyanidin, delphinidin Molybdenum did not affect the color of flowers containing pelargonidin or pelargonidin anc cyanidin. Strong bathochromic shifts with molybdenum were also observed in extracts containing delphinidin glycoside or delphinidin spots on thin layer chromatograms. Furthermore, the flowei color of Eustoma grandiflorum 'Exrosa Blue Flash', which was grown in hydroponics suppliec with ammonium molybdate (Mo:l mM) before anthesis became bluish.
Root-zone-hypoxia-intolerant tomato plants (Lycopersicon esculentum Mill., cv. House-Momotaro) were grown in nutrient solution with a dissolved O2 concentration of either 1 mg·liter-1 (hypoxia) or 6 mg·liter-1 (normoxia) for 7 days starting at the fifth leaf stage. The dissolved O2 levels in nutrient solution did not affect polyamine biosynthetic enzyme activities and free polyamine contents in the roots. Plants in hypoxic nutrient solution grew poorly and exhibited a significant increase in lactate dehydrogenase activity and lactate content in the roots compared with those grown in normoxic nutrient solution. However, preincubation of plants in 0.5 mM putrescine-containing normoxic nutrient solution for 6 hr promoted root growth and inhibited the rise of lactate fermentation in the roots after day 5 under hypoxia. These results indicate that putrescine interferes with hypoxically induced lactate fermentation in the roots; it alleviates hypoxia injury of roots and increases the root-zone hypoxia tolerance of tomato plants.
The plant regeneration process in onion (Allium cepa L.) calli was investigated histologically. In the plant regeneration process from the calli, embryo-like structures formed on the surface of the calli, that developed into plantlets. Several developmental stages of these embryo-like structures were recorded histologically. These embryo-like structures progressed from a globular embryo to a bipolar embryonic shoot and root apices which were connected with vascular bundles. On the other hand, the shoot-like structures, having abnormal, hyperhydrated appearance, seemingly formed via organogenesis. However, these shoot-like structures did not develop into shoots or plantlets. Therefore, it was concluded that the regeneration of the plantlets occurred through somatic embryogenesis.
Possible involvement of polyamines in the cold-acclimatory increase in chilling tolerance in cucumber (Cucumis sativus L.) was investigated. When the first leaf was fully expanded, chill-sensitive cultivar Suyo and chill-tolerant cultivar Jinchun No.3 plants were exposed to 10/8°C (day/night, a 12-hr photoperiod) under moderate light for 2 days to acclimate to cold. These plants together with control plants grown at 28/22°C were chilled at 3°C in darkness for 24 hr and returned to 28/22°C for another 24 hr. Chilling injury symptoms that developed in control leaves during rewarming were more severe in 'Suyo' than in 'Jinchun No.3'. In contrast, acclimation-treated leaves suffered little if any chilling injury in both cultivars. Cold-acclimated leaves of 'Jinchun No.3' showed a transient and marked increase in spermidine content during chilling and rewarming compared to that before chilling. In cold-acclimated leaves of 'Suyo', however, chillmediated changes in polyamine content were much smaller than those of 'Jinchun No.3'. Such absence of enhanced polyamine biosynthesis in cold-acclimated 'Suyo' leaves indicates that polyamines are not indispensable for the cold-acclimatization increase in chilling tolerance in cucumber.
To reduce labor costs in the cultivation of Japanese persimmon which is prone to be too vigorous, a horizontal trellis training system was attempted as a practical method for lowering the tree height. The frameworks of an open center, 3.6 m high 'Matsumotowase-Fuyu' Japanese persimmon trees were altered to a horizontal frame at 1.8 m height on February 1992 by cutting back secondary scaffold branches at 1.5. to 1.6 m above ground level. The tree growth, yields and fruit quality of the altered trees were compared with the open-center free-standing trees control. One year after altering the framework, the canopy area on horizontally trellised trees expanded vigorously, compared with the control group. After pruning, the trees with altered the framework were left with twenty percent more lateral branches than the open center free-standing trees. Two years after altering, the number of shoots per canopy area was greater in the treated trees than in the control, but the number of shoots per lateral branches and mean shoot length did not significantly differ from the control group. Annual fruit yield was 300 kg/a higher in the horizontal trellis system than that of the unaltered free standing system group, and the number of fruits per canopy area exceeded 10 fruits/m2. Over 4-year period, the horizontally trellised trees produced more flowers per lateral branch than did the open center free-standing ones. Physiological fruit drop rates were lower in horizontally trellised trees than in those of the control. Fruit on the former was significantly heavier than that on the letter. The percentage of fruit weighing more than 260 g accounted for 61.2% of the total yield in horizontally trellised trees. During the period of 80 days after blossoming to harvest, fruit diameter increased significantly faster on horizontally trellised trees than that on the free standing trees. Similarly, the commencement of fruit skin coloring and harvest time was advanced in the treated trees compared with those of the control. In conclusion, by lowering tree height the horizontal trellis training system achieves the following: decreased harvest and pruning costs, increased yield and fruit weight, improved fruit quality, and advanced maturation. These advantages indicate that this system has a strong potential as a training system that will be used extensively in the near future.
The conventionally used open rockwool cultivation system has a problem of causing environmental pollution because the nutrient solution drained from the bed is discarded to the environment. We constructed a new rockwool system for tomato cultivation with a device to reuse the nutrient solution. With this revised system, freshly prepared nutrient solution is supplied to plants and its drainage is collected in the tank A. When this tank is filled to a preset capacity, the solution in this tank is supplied to plants and its drainage is collected in the tank B. When the tank A becomes empty but the tank B is not saturated, fresh nutrient solution is supplied to plants until the tank B is filled with used nutrient solution. Then, the nutrient solution in the tank B is supplied to plants and its drainage is collected in the tank C. When the solution in the tank C is saturated, nutrient solution in this tank is supplied to plants and its drainage is collected in the waste tank and discarded. This procedure is repeated until crop cultivation is halted. In this study, tomato (Lycopersicon esculentum Mill., cv. 'House Momotaro') was cultivated in the glasshouse for 6 months from September to March by using the revised semi-closed rockwool system and the conventional open rockwool system. Plant densities were 2000 plants/10a. The concentrations of nutrient elements in the rockwool slub differed with the systems, and Na concentrations were much higher in the revised system than in the conventional system. However, plant growth and fruit yields were not significantly different between the two systems. The revised semi-closed system showed a 87 to 99% reduction in the amount of nutrient elements discarded as compared with the conventional system. Possible problems in using the revised rockwool system are discussed.
To speciate the edible, indigenous Dioscorea in Japan, 425 plants collected from 24 regions were classified as Dioscorea japonica Thunb., although some plants have leaf morphology characteristic of Dioscorea opposita Thunb. Typical D. japonica specimen were collected from 21 regions, whereas those with characteristics of D. opposita were collected from 17 regions. The former were collected exclusively from seven regions with mild climate, while the latter were collected from three regions with cold climate, indicating that the two species were adapted to different climatic zones. When D. japonica and cultivated D. opposita were hand-pollinated to observe the hybrid seed formation, few normal seeds were produced, indicating cross-incompatibility. Similarly, D. japonica and plants with characteristics of D. opposita were also incompatible, producing no normal seeds. Many crosses within D. japonica and those between D. japonica with characteristics of D. opposita and locally cultivated D. opposita produced viable seeds. These findings indicate that cross-incompatible plants with characteristics of D. opposita should not be classified as D. japonica but rather as D. opposita or its close relative.
Cultural conditions of mother plants were investigated to establish a vegetative propagation method for sweet pepper (Capsicum annuum L.). Planting densities of mother plants ranging from 30 m-2 to 180 m-2 in a deep flow hydroponic system revealed that the lower the density, the higher was the yield per mother plant, but conversely, the higher the density, the higher the yield was per unit planting area. When the mother plants were cultivated in the same hydroponic system, the roots of some plants turned brown, causing the plants to wilt and die, indicating a shortage of dissolved oxygen in the solution. Therefore, three kinds of synthetic root-anchoring substrates were examined and compared with hydroponics. Two types of transplants, cuttings and grafts, were used as mother test plants. The appearance and spread of the wilting symptoms were much slower with three anchorages than they were in the hydroponic culture. More than 80% of the grafted plants survived over a 10-month period on all substrates, whereas in the hydroponic plots, the grafts died within eight months. The yield of shoots was about the same among the three anchorages examined. Grafted mother plants yielded about twice the shoots than did the cuttings during 10-month cultivation period. By this method, 90 shoots can be harvested every week from one square meter of planting area continuously for one or more years.
The effects of recuperating condition of grafting of sweet pepper scions harvested from a common mother plant were investigated. When mature sweet pepper shoots were grafted onto rootstocks of different cultivars, the success rate was about 75%. However, quite a few leaves fell from almost all grafts during three weeks of recuperation and acclimatization treatment. Growth was repressed on grafts in which three or more leaves fell and their fruit yields were rather low. In contrast, growth and yields of the grafts in which one or two leaves fell were equal to control seedlings; these were designated as good transplants. Examination of exposing stock/sion combinations to 15°C to 25°C for 4 to 7 days on percentage take revealed that the union healed fastest at 22.5°C; it was slower at lower temperatures. The higher the temperature, the more leaves fell. Transplant yield was highest (92%) when the temperature was maintained at 15°C for first four days and then raised stepwise daily to 17.5°C, 20°C, and 25°C on the seventh day. The grafts were transferred for acclimatization. The percentage take of grafts and yield of good transplants differed among cultivars used for rootstock, but a wide variety of sweet peppers served as good rootstocks.
Mericlones of Brassolaeliocattleya Shinmei 'Sanyang' transplanted from flasks to pots with sphagnum moss were acclimated for 4 weeks in growth cabinets controlled at 15°C, 25°C and 35°C under 50 μmol · m-2 · s-1 for 16-hr photoperiod with fluorescent lamps. Except for root CAT activity that increased at 25°C, superoxide dismutase (SOD), ascorbate peroxidase (APX) and catalase (CAT) activities in leaves and roots fluctuated slightly. However, those activities at 15°C and 35°C, initially changed significantly after the onset of the treatments; they became stable during the rest of the acclimation period. Based on the antioxidative enzyme activities, the responses to thermal stress were greater in roots than in leaves. These results indicate the significance of managing the root environment at transplantation time. SOD activities that were highest at 35°C, followed by those at 15°C, clearly demonstrate the effects of acclimation temperatures (thermal stress ) on both leaves and roots. Thermal effects on APX and CAT differed between leaves and roots. SOD activities in both leaves and roots as affected by the high temperature became smoothly stabilized. CAT activated for 48 hrs after the onset of the acclimation treatment reverted to its initial level and remained so for several more weeks. Activities in SOD, APX, and CAT in roots that increased at 15°C indicate that cattleya plants are heat-but not cold-resistant.
Mericlone plantets of Cymbidium Yamba 'Bayswater' transplanted in pots with sphagnum moss were acclimatized for 4 weeks at 15°C, 25°C and 35°C in growth cabinets illuminated at 50 μmol·m-2·s-1 during a 16-hr photoperiod. At 25°C, superoxide dismutase (SOD), ascorbate peroxidase (APX) and catalase (CAT) activities of both leaf and root, except SOD activity of root and CAT activity of leaf, fluctuated slightly during acclimatization. The 35°C and 15°C treatments induced marked increases in activities of these enzymes within 48 hr after onset of the treatment. SOD activity of both leaf and root was the highest at the low temperature treatment, while that at 35°C was intermediate. Temperature of 15°C increased both APX and CAT activities of leaf, but had no effect on the enzyme activities of roots. Contrary to this, temperature of 35°C reduced APX and CAT activities of root which continued during the acclimatization; the effect was greater on roots than on leaves. These findings indicate that cymbidium seedlings are tolerant of low temperatures and that antioxidative enzymes may be appropriate indicators for acclimatization.
Changes in the antioxidative enzyme activities and substrates of broccoli (Brassica oleracea L.) flower buds stored at 8, 16 and 24°C were investigated; the correlations between senescence and these functions are discussed. The chlorophyll and protein content decreased with time; the rate of decrease was faster at the high temperature than at lower ones. The malondialdehyde content increased with increasing temperature and time. The correlations between these senescence indices and antioxidative enzyme activities differed with storage temperature. At 8°C, senescence did not progress; no relation was observed. However, at 16TC, catalase (CAT) and ascorbate peroxidase (APX) were related to the senescence indices, whereas superoxide dismutase (SOD), CAT, APX and peroxidase (POX) were highly correlated to them at 24°C. However, at all temperatures high correlations between the senescence indices and content of antioxidative substances, such as ascorbic acid and /3 -carotene, existed. These results indicate that increasing antioxidative enzyme activities and the concurrent reduction in substrates are closely related to senescence of broccoli flower buds.