Recently, attempts have been made to produce sweet cherry in the warm region of Japan, although the occurrence of double fruit, resulting from double pistil formation, and poor fruit set due to frequent physiological fruit drop have become serious problems preventing stable production; however, the inducing factors have not been clarified. Therefore, we investigated the effects of environmental and nutritional conditions on the occurrence of double pistils and poor fruit set. Based on those results, we studied the regulation of pistil doubling and fruit set in this region. In this review, we summarize our studies on the reproduction of sweet cherry in a warm climate.

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We investigated female and male gamete formation in a pummelo [Citrus maxima (Burm.) Merr.] haploid. During female gamete formation, no embryo-sac mother cell (EMC) was formed in ovules, and consequently no normal embryo sac was observed at anthesis, which was confirmed as the cause of female sterility in the haploid. During male gamete formation, on the other hand, meiosis in the pollen mother cells (PMCs) of the haploid occurred twice, but abnormalities were observed in most dividing cells. In some dividing cells, univalents did not distribute to the opposite poles at anaphase I; instead, they remained near the equatorial plate. The nine univalents then performed mitosis, which distributed equally forward opposite poles. Furthermore, at the tetrad stage, the tetrad comprised 99.3% of the ‘Banpeiyu’ pummelo, whereas sporads from monads to hexads with a relatively high frequency of dyads (24.7%) were produced in the haploid. These results suggest that fertile pollen grains observed in the haploid pummelo were produced by abnormalities in the first meiotic division such as first division restitution (FDR).

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The effects of initiation timing of drought stress on the carbohydrate content and growth of Japanese apricot (Prunus mume Sieb. et Zucc.) ‘Nanko’ tree were investigated. Three-year-old trees were subjected to drought stress for three months in May (‘Spring’) and August (‘Summer’), respectively. Irrigation was started immediately after drought stress treatment had finished. The starch concentration in the roots of stressed trees increased in both ‘Spring’ and ‘Summer’ two months after starting drought stress treatment and rapidly decreased just after starting irrigation in ‘Spring’; however, it still temporarily increased in ‘Summer’. These different results were attributed to seasonal changes in the carbohydrate demand. The dry matter weight of each tree organ in February of the following year was suppressed by drought stress, particularly in ‘Spring’. This result indicates that, if a tree suffers drought stress in spring, vegetative growth is suppressed more seriously than in summer and tree growth, declined by suffering from severe and long-term drought stress, will hardly recover even the tree is re-irrigated. The total starch in all organs of the drought-stressed trees in February of the following year was significantly less than that in well-irrigated trees. These results indicate that severe drought stress for three months inhibits not only current tree growth but also the accumulation of carbohydrates that is necessary for the following year’s growth. Hence, irrigation to avoid a fatal growth decline due to severe drought stress is needed during the current growth stage, especially in the early growth stage in spring.

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The use of tray grown transplants is becoming popular for substrate strawberry production. Although tray plant production with hanging runner cuttings is a laborsaving propagation procedure for forcing of June-bearing strawberries, the tray grown plants are inferior to pot grown plants in terms of earliness and uniformity of flowering. The crowns of rooted tray plants are often deeply drawn into medium by their own roots. The effect of crown depth, age, and size of tray plants on flowering of June-bearing strawberry (Fragaria × ananassa Duch. ‘Nyoho’) were investigated. Tissue temperature around the apical meristem was lower, and earlier and more uniform flower bud differentiation was obtained in the crown stripped or shallow-grown plants compared to deeply embedded plants. Flowering was later in young and small tray plants compared to aged large plants. By applying crown stripping, early and uniform flowering could be obtained even in the young and small tray plants. The variation in the depth of crown was clarified to be a cause of poor flowering performance of the tray grown strawberry plants. To obtain productive tray grown transplants, crown stripping would be an efficient procedure in practice.

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For practical use of the seed propagation type of F₁ hybrid strawberry, high germination percentage and germination uniformity are necessary. The effects of scarification with concentrated sulfuric acid and matric priming on seed germination of this strawberry were investigated in order to improve the germination performance. Open-pollinated seeds of ‘Tochiotome’ and seeds from the seed propagation type of the F₁ hybrid strawberry cultivar ‘Chiba F-1 go’, bred by ourselves, were used. Germination tests were carried out on a temperature-gradient plate to investigate the response to temperature. The number of germinated seeds was counted for 7 days after sowing. The final germination percentage (FGP) of seeds scarified with 36 N sulfuric acid for 10 min exceeded 83% in the optimal temperature range of around 24–27°C, whereas untreated seeds did not germinate. FGP increased to more than 82% in the wide temperature range of 18–32°C with matric priming in vermiculite (−1.5 MPa) for 12 days after scarification. The effect of scarification time on germination was investigated for the seeds of ‘Chiba F-1 go’. The highest percentage (84%) was obtained in the seeds scarified for 35 min. Furthermore, the germination speed and uniformity increased with extension of the duration of matric priming from 0 to 14 days. Germination performance of the seeds of ‘Chiba F-1 go’ was improved for practical use by scarification with concentrated sulfuric acid and scarification plus matric priming.

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We evaluated varietal differences in everbearing strawberry (Fragaria × ananassa Duch.) and selection indicators of flowering pattern by investigating the numbers of inflorescences and individual flowers together with their flowering dates from spring to autumn. Highly significant (P < 0.001) differences among varieties in these traits indicate a genetic basis for the strength of everbearing. The results suggest that parentage is involved in the strength of everbearing. Varieties in the ‘Oishi-shikinari’ lineage flowered earlier in summer, with fewer leaves emerging between spring and summer inflorescences, and had more inflorescences than the ‘Kaho’ and F. virginiana Duch. ssp. glauca (Wats.) Staudt lineages. The earliness of flowering of June-bearing parents in spring also seemed to influence their offspring’s first flowering date of summer inflorescences. Thus, the use of early-flowering June-bearers may facilitate the breeding of strong everbearing varieties. These lines of evidence suggest that the choice of mating parents is crucial for breeding focused on the ‘strength’ of everbearing. Significant correlations (r = −0.65 to −0.78) were found between two phenological traits (the first flowering date of summer inflorescences and the number of leaves emerging between spring and summer inflorescences) and traits representing the strength of everbearing, including the numbers of inflorescences and individual flowers. These results suggest the appropriateness of those phenological traits as selection indicators for the flowering pattern of everbearing.

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We investigated the effects of ascorbic acid (AsA) or etiolation treatments on the regeneration of shoots from cut ends of tomato stems. For the AsA treatment, AsA solution was applied to leaves of tomato plants immediately after cutting the main stem. The etiolation treatment consisted of covering the cut stem with an aluminum cap. When applied individually, the AsA or etiolation treatments resulted in increased numbers of shoots regenerated from the cut stem. However, application of both treatments simultaneously did not have a synergetic effect on the number of shoots regenerated. To clarify the mechanisms by which these treatments promoted shoot regeneration, we determined the effects of AsA or etiolation treatments on scavenging of reactive oxygen species (ROS) by antioxidant enzymes and phenylpropanoid metabolism in the cut ends of tomato stems during the shoot regeneration process. In this study, activities of antioxidant enzymes (superoxide dismutase, ascorbate peroxidase, catalase) were higher in most of the stems that received AsA or etiolation treatments, compared with those of the control. In addition, compared with the control, plants treated with individual AsA or etiolation had lower levels of hydrogen peroxide, malondialdehyde, and phenols, and lower phenylalanine ammonia-lyase activity. These results indicated that the promotive effects of individual AsA or etiolation treatments on shoot regeneration from cut tomato stems can be attributed to the same mechanism, which involves the high activity of antioxidant enzyme, suppression of oxidative stress and phenol accumulation.

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Chinese Hami melon consists of the varieties cassaba, chandalak, ameri, and zard. To show their genetic diversity, 120 melon accessions, including 24 accessions of Hami melon, were analyzed using molecular markers of nuclear and cytoplasmic genomes. All Hami melon accessions were classified as the large-seed type with seed length longer than 9 mm, like US and Spanish Inodorus melon. Conomon accessions grown in east China were all the small-seed type. Both large- and small-seed types were in landraces from Iran, Afghanistan, Pakistan, and Central Asia. Analysis of an SNP in the PS-ID region (Rpl16-Rpl14) and size polymorphism of ccSSR7 showed that the melon accessions consisted of three chloroplast genome types, that is, maternal lineages. Hami melon accessions were T/338 bp type, which differed from Spanish melon and US Honey Dew (T/333 bp type), indicating a different maternal lineage within group Inodorus. The gene diversity (D), calculated from random amplified polymorphic DNA (RAPD) and simple sequence repeat (SSR) polymorphism, was 0.476 in 120 melon accessions; the largest diversity was in Central Asian accessions (D = 0.377) but was low for Hami melon accessions (D = 0.243), even though Hami melon has diverse morphological traits, earliness, and shelf life. Reflecting such small genetic diversity, Hami melon accessions of vars. ameri and zard were grouped into cluster II, except for one accession, by the unweighted pair group method and the arithmetic mean (UPGMA) cluster analysis. Variety chandalak with distinct characters, such as early maturing and poor shelf life, was assigned to clusters IV and VI, indicating inter-varietal genetic differentiation within Hami melon. Three accessions from Turkmenistan and Afghanistan, with large seeds and T/338 bp type of chloroplast genome, were classified as cluster II with Hami melon accessions of vars. ameri and zard. We therefore concluded that Hami melon may have been transmitted from the west. The small-seed type melon of group Conomon grown in east China may have been introduced into China independently of Hami melon, because it had the A/338 bp type of the chloroplast genome and was clustered distantly from Hami melon according to nuclear genome analysis.

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The most common cucumber plants (Cucumis sativus L.) show monoecious sex expression and produce both male and female flowers on the same plant, whereas plants of the gynoecious type produce only female flowers under natural conditions. Ethylene is a plant hormone that affects sex differentiation in cucumber plants. In the gynoecious cucumber, application of the ethylene biosynthesis inhibitor aminoethoxyvinyl glycine (AVG) induced only male flowers, whereas application of the ethylene action inhibitor silver nitrate (AgNO₃) induced male and morphologically bisexual flowers. To investigate whether the morphologically bisexual flowers that were induced by AgNO₃ in gynoecious cucumber plants have functional sexual organs, we analyzed the function of pistils and stamens. Seeds were produced by cross-fertilization and the pollen tubes were elongated on sucrose medium in eight of the twenty-five morphologically bisexual flowers. These results show that the application of AgNO₃ to gynoecious cucumber plants produces functional bisexual flowers. In functional bisexual flowers, the length of pistils was similar to that of the female flowers of gynoecious cucumber plants and the length of stamens was similar to that of male and bisexual flowers of andromonoecious cucumber plants. In contrast, stamen length was inversely proportional to pistil length in the group of morphologically bisexual flowers that were induced by AgNO₃. These results suggest that the morphology of the sexual organs is different in morphologically bisexual flowers and in functional bisexual flowers. It is possible that the functional bisexual flowers that were induced by AgNO₃ in gynoecious cucumber plants are the result of exclusive blockade of ethylene signals that inhibit stamen development.

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The effects of storage temperature (5°C, 10°C, and 15°C) on the appearance, weight, and ascorbic acid content of 3 asparagus cultivars—‘UC157’, ‘Gijnlim’, and ‘Purple Passion’—cultivated as green asparagus in open fields were investigated over a 4-day storage period. In addition, we investigated the respiration rate (CO₂ production rate), which is closely related to the qualitative deterioration of fresh produce. Among the 3 cultivars, ‘Gijnlim’ had the loosest spear-head and the highest ascorbic acid content immediately after harvest. The extent of opening of the spear-head during the 4-day storage period varied among the cultivars, and was most marked in ‘Gijnlim’ and was least in ‘Purple Passion’. Discoloration of the cut end of the spear was found to be dependent upon the storage temperature to a greater extent than the individual cultivars. ‘Gijnlim’ had marked discoloration at 10°C. Moreover, ‘Gijnlim’ had the largest decline in weight among the 3 cultivars at each of the 3 temperatures examined. A similar tendency was observed in the decline in ascorbic acid content. The respiration rate of ‘Purple Passion’ within 2–8 h after harvest tended to be smaller than that of ‘UC157’ and ‘Gijnlim’. These findings suggested that there are differences among the cultivars with respect to the rates of changes in postharvest quality. ‘Gijnlim’ tended to deteriorate faster than ‘UC157’ and ‘Purple Passion’, suggesting that strict temperature control and/or packaging might be required to maintain the quality of ‘Gijnlim’ harvested in the spring.

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An aseptic bioassay system to estimate allelopathy in asparagus calluses was established. Allelopathic activities of calluses were measured according to the callus packed cell volume (PCV) by means of the sandwich method, and remarkable inhibition of acceptor plants was observed by the addition of over 0.1 mL PCV. When female and male calluses were separately used for the sandwich method, there was no sexual difference in allelopathic activity. To detect the allelopathic activities of the callus cells in detail, we improved the plant box method that substituted the calluses for the seedlings, and serious inhibition of acceptor plants was observed with the addition of over 0.35 mL PCV as donor material. Allelopathic activities were accelerated by irradiating the calluses with light-emitting diodes (LEDs) prior to performing the aseptic bioassay. It also seemed that the light quality would affect their activities. The allelopathic activity appeared intensely with irradiation of the calluses with a blue LED. The aseptic bioassay system that employed LED-irradiated calluses established here could accelerate effectively the isolation and identification of allelochemical(s).

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Petal senescence is a highly regulated developmental process that is controlled by multiple genes. We examined the regulation of autophagy, which has been thought to be involved in petal senescence in Japanese morning glory. Five of six isolated autophagy-related gene 8 (ATG8) homologs in Japanese morning glory, InATG8a, b, d, e, and f were highly expressed in senescing petal limbs, indicating that multiple members of the InATG8 gene family are involved in the regulation of autophagy during petal senescence. Suppressed InATG8f expression in transgenic plants altered neither autophagic activity nor petal senescence, suggesting that some members of the InATG8 gene family have redundant function in the induction of autophagy in petal senescence. It was confirmed from these findings that autophagy is induced during petal senescence in Japanese morning glory, suggesting that autophagy plays an important role in petal senescence.

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A case study was conducted to evaluate the quality of indoor air and the health-related parameters of indoor occupants with the consideration of indoor-plant placement in the office buildings in Seoul, Korea from October, 2006 to July, 2007. The office buildings with more than seven floors were categorized into two groups. One group was composed of six newly-built buildings established in 2005 to 2006 and the other group was composed of six aged buildings established in 1990 to 1992. An office room on the 3rd floor was chosen as the place with indoor plants and on the 4th floor as the place without indoor plants. The quality of indoor air was estimated using the concentrations of air-borne fine particles including formaldehyde and other volatile organic compounds (VOCs)—benzene, toluene, ethylene, and xylene (BTEX). The physical condition of indoor occupants was evaluated based on certain health-related parameters such as the symptom degree of sick building syndrome (SBS) and the scale of symptom checklist (90) revised (SCL-90-R). The concentration of formaldehyde was decreased not by the individual application of ventilation or indoor-plant placement but by the combined application of the two factors as evidenced by reductions from 80.8 to 66.4 μg·m⁻³ in the newly-built building and from 23.3 to 18.6 μg·m⁻³ in the aged building. The concentrations of BTEX varied with indoor conditions. In office rooms with high concentrations of BTEX, these concentrations were obviously reduced by the individual application of ventilation but hardly reduced by the individual application of indoor-plant placement. The indoor occupants of the newly-built buildings perceived little improvement in the symptom degree of SBS by the individual application of ventilation (changing from 19 to 15 points) or indoor-plant placement (changing from 26 to 25). In contrast, the indoor occupants of the aged buildings felt a good improvement in the symptom degree of SBS by the combined application of ventilation and indoor-plant placement, reducing from 23 to 14 points. Observing the mental health of indoor occupants using SCL-90-R, the various results did not show a clear tendency. It could be tentatively postulated that the individual application of ventilation or indoor-plant placement in the office room failed to make sufficient improvement in the mental health of indoor occupants.

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The role of phenylalanine ammonialyase (PAL), polyphenol oxidase (PPO), and peroxidase (POD) in browning of fresh-cut galangal (Alpinia siamense K. Schum, ‘Kha Ta Daeng’) rhizome was investigated by determining changes in colour, total phenolic content (TPC), and the activities of these enzymes in the exterior (subepidermis and cortex) and the interior (vascular) tissues within 24 h under ambient conditions (29 ± 1°C and 86 ± 2% RH) after wounding. Browning of the peeled (exterior) and the cut (interior) surface of the rhizome increased progressively after wounding, but the peeled surface showed more browning than the cut surface. In the exterior tissue, TPC increased slightly from 190 to 220 mg gallic acid equivalent/100 g FW over the time of peeling, while PAL activity significantly increased by 37% of the initial level during the first 6 h after peeling, and declined thereafter. TPC in the interior tissue showed the same trend as the exterior tissue with a 10% lower in quantity, while PAL activity in the interior tissue only slightly increased. Changes in TPC and PAL activity in both exterior and interior tissues showed no significant correlations to any of the browning parameters over time (r = 0.16 to 0.48 and r = 0.01 to 0.50, respectively). PPO activity in the exterior tissue increased by 30% of the initial value during the first 6 h after peeling coupled with a slight increase in surface browning of fresh-cut galangal, while the POD activity remained unchanged. As browning progressed, both PPO and POD activities markedly increased in the exterior tissue and showed significant correlations to browning parameters, except for hue angle (r = 0.66 to 0.73 and r = 0.87 to 0.92, respectively). Histochemical assay for PPO showed that the site of browning began on the peeled surface, then gradually progressed to the cut surface, while that for POD occurred immediately on the entire wounded surface and no browning progression was observed, indicating that browning of fresh-cut galangal was likely mediated by PPO. However, POD may likely be involved in the lignification process in response to wounding because, from a microscopic examination, lignin was deposited on the parenchyma cell walls of the wounded exterior of the galangal rhizome.

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The mutated carnation ethylene receptor gene Dc-ETR1nr was introduced into Torenia fournieri Lind. This gene contains a missense mutation causing conversion of a Pro³⁶ residue of the carnation ethylene receptor protein Dc-ETR1 to Leu³⁶, as occurs with the tomato mutant gene Never-ripe (Nr). Agrobacterium transformation of Torenia was performed, and four putative transgenic plants with Dc-ETR1nr were obtained. Real-time RT-PCR analysis confirmed Dc-ETR1nr mRNA expression in all transgenic plants. Unlike wild-type plants and 1-aminocyclopropane-1-carboxylic acid oxidase (ACO) transgenic plants, none of the transgenic plants showed flower abscission in response to ethylene treatment. Flower life in all Dc-ETR1nr transgenic plants following wounding or ethylene treatment was longer than that in wild-type plants. Levels of autocatalytic ethylene production in all transgenic plants following wounding or pollination treatment were lower than those in wild-type plants. These results indicate that transgenic plants expressing Dc-ETR1nr have reduced ethylene sensitivity, resulting in inhibition of autocatalytic ethylene production and flower senescence.

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