Search

The translocation of calcium (Ca) within the tomato plant and the causes of Ca deficiency, a factor associated with blossom-end rot (BER) in fruit, are still a matter of conjecture. The objective of this study was to determine the effect of defoliation on BER incidence and Ca transport into different size tomato fruit cultivars. Four experiments were conducted. The start and end dates for each experiment were; 14 March–2 May, 22 July–23 August, 30 August–7 October 2017, and 20 May–25 June 2018, for experiments 1, 2, 3, and 4, respectively. Five tomato cultivars including one large (‘Momotaro fight (MF)’, ≥ 200 g), three medium (‘Lui 60 (L60)’, ‘Tio cook (TC)’, and ‘Cindy sweet (CS)’, 30–80 g), and one small (‘Pepe (PP)’, ≤ 20 g) fruit cultivars, respectively, were grown under moderate water stress controlled by a combination of root zone restriction and solar mediated fertigation. Leaf area of plants was reduced by 20–30% by removing alternate leaflets on all leaves. Defoliation significantly reduced BER in all experiments. In experiment 4, no BER was observed in defoliated plants of L60 and PP, and in MF and TC, BER incidence decreased to a quarter of the control. Defoliation increased the fruit growth rate (FGR) in experiment 1, in which the temperature was the lowest, by a ratio of 1.42 and by 1.39 in experiment 4, in which the radiation was strongest and day length longest. Defoliation increased the rate of daily Ca transport into fruit (CTR) in MF, L60, TC, CS, and PP by average ratios of 1.64, 1.55, 1.35, 1.30, and 1.13, respectively. The increase in CTR in defoliated plants was highest in experiment 4 with a ratio of 1.68 followed by 1.37, 1.33, and 1.28 in experiments 1, 3, and 2, respectively. Defoliation increased both FGR and CTR and there were significant linear relationships between them. However, the degree of increase was larger in CTR than that in FGR, especially in the BER-sensitive large fruit cultivar MF, and defoliation increased the total Ca concentration in fruit accordingly. We conclude that under moderate water stress by root zone restriction and certain other BER inductive conditions, defoliation could be a promising approach to reduce BER incidence by improving Ca nutrition in susceptible large fruit cultivars.

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.

To shorten the breeding cycle in spinach, the effect of photoperiod after bolting on the expression of gynomonoecy was investigated by employing selfed-progeny of a gynomonoecious spinach plant. Seedlings were induced to bolt by an initial exposure to 16-h photoperiod under 140 μmol·m−2·s−1 PPFD and 20°C in a growth chamber for 3 weeks after sowing. When transferred to an 8-h photoperiod of the same PPFD, flower stalk elongation and flowering were severely inhibited; the frequency of gynomonoecious plants decreased to about a half of those under 12- and 16-h photoperiods. Under the short-day treatment, a few nodes with hermaphroditic flowers developed; the frequency of hermaphroditic flowers on gynomonoecious plants was 30, 39, and 63% under 8-, 12-, and 16-h photoperiod, respectively. Even when the light intensity under the 8-h photoperiod was doubled, the flower stalks elongated little, while 46% of the plants did not flower. When 8-h photoperiod under 280 μmol·m−2·s−1 PPFD was extended to 16-h, by using an incandescent lamp with an intensity of 10 μmol·m−2·s−1 PPFD, the seedlings produced flower stalks that were longer than those grown under 16-h photoperiod and 140 μmol·m−2·s−1 PPFD, and all plants flowered. There was no difference in the frequency of gynomonoecious plants and hermaphroditic flowers in both 16-h photoperiodic regimes. Extending the photoperiod to 24-h (constant light) from 8-h photoperiod at 280 μmol·m−2·s−1 with incandescent lights promoted flower stalk elongation more than did that by extending it to 16-h. However, the frequency of hermaphroditic flowers was almost the same in both the 16- and 24-h photoperiodic regimes. Thus, the expression of gynomonoecy after bolting in spinach was inhibited strongly under a short photoperiod and was promoted significantly by extending the photoperiod to 16-h, but extending the photoperiod to 24-h had no further effect. Therefore, it is important to extend the photoperiod to around 16-h for an efficient production of self-fertilized seeds in gynomonoecious spinach plants during the season with short photoperiods.

For an efficient harvest of self-fertilized seeds in spinach, the effect of temperature on the expression of gynomonoecy was studied by employing selfed-seed populations from three gynomonoecious plants that produced 525, 359 and 186 seeds/plant. These selfed-seed populations were named P-1, P-2, and P-3, respectively. Seeds, sown monthly from December to March in an unheated glasshouse, revealed that the frequency of gynomonoecious plants was highest in P-1 and lowest in P-3 at any sowing time. In December-sown seeds of P-1, the frequency of gynomonoecious plants was 33%; as the sowing time was delayed, the frequency of gynomonoecious plants increased until it reached 100% in the March-sown seeds. Similar results were obtained in a growth chamber kept at 15, 20 and 25°C, and under 16 h photoperiod with 120 μmol · m−2 · s−1 PPFD. However, the frequency of hermaphroditic flowers on gynomonoecious plants was affected by temperature in all three populations; it was lowest at 15°C and highest at 20°C. At 25°C, hermaphroditic flowers occurred near the shoot apex, but the number of nodes with hermaphroditic flowers was equal or less than at 20°C due to the delay in bolting and/or reduced plant height. When seedlings were transferred to 25°C after bolting was induced at 20°C for 18 days, the mean plant height was reduced but the number of nodes with hermaphroditic flowers was unaffected. This cultural manipulation seems to be advantageous for seed production because it suggests that a line with a strong expression of gynomonoecy can be selected to maximize the production of self-fertilized spinach seeds.

Japanese and European strawberry (Fragaria × ananassa Duch.) cultivars were analyzed for their differences in their concentration and composition of anthocyanins. Within a fruit, the concentration of total anthocyanins is higher in epidermal tissues than in inner cortex or pith for all cultivars, but among cultivars, differences in the concentration were greater in the inner flesh compared to the epidermal tissues. The pigment in inner flesh was significantly less concentrated in the newly released Japanese cultivars than in the European cultivars, ‘Elsanta’ and ‘Darselect’, or the old Japanese cultivar ‘Hokowase’. Pelargonidin 3-glucoside was the predominant pigment except for achenes. In achenes, the compositions of cyanidin derivatives and malonylated anthocyanins were extremely high compared to the other tissues. Considerable amounts of cyanidin 3-malonylglucoside, which has not been reported previously and pelargonidin 3-malonylglucoside occurred in achenes of all cultivars. The epidermal tissues of ‘Toyonoka’, ‘Sachinoka’ and ‘Ai-Berry’ contained only a trace level of malonylated anthocyanins; the achenes also had low concentration of the pigments compared to other cultivars. With these results, the functions and expression of Amg, the single dominant gene that supposedly controls the synthesis of malonylated anthocyanins in the strawberry receptacle, are discussed.

Leaf structure and photosynthetic properties of an individual leaf and a whole plant were compared between resetting and bolting plants in Eustoma grandiflorum (Raf.) Shinn. Leaves on bolting plants (BP) were thinner, had smaller mesophyll cells, and lower chlorophyll content compared to the leaves on resetting plants (RP). The photosynthetic capacity of upper leaves on a leaf area basis was lower in BP than in RP. On a leaf area basis, the amount of 13C incorporated into upper leaves of BP was less than RP, but that into lower leaves of BP was significantly larger than RP. On a dry weight basis, the total amount of 13C incorporated into BP, similar to the relative growth rate, was 1.6 times larger than that fixed on RP. These results indicate that rapid growth in BP does not depend on changes in the photosynthetic capacity of leaves, but on the increase in leaf area and improvement of light-intercepting characteristics of the whole plant.

培養液に使用可能な原水中塩濃度の限界を明らかにするため，イチゴ‘女峰’をピートバッグ（28 × 80 cm，培地量18 liter，8株植え）で栽培し，水道水（EC15 mS/m; Na, 0.35; Cl, 0.29 mM）で作成した培養液へのNaCl添加がイチゴの生育，収量に及ぼす影響について検討した．NaCl (0, 4, 8, 12 mM）以外の基本培養液濃度（NO3-N, 8; NH4-N, 0.85; P, 0.85; K, 3.8; Ca, 2.05; Mg, 0.93 mM）は，季節に応じて50～100％の間で変化させた．葉柄中のNaとClの濃度は，NaCl濃度が高くなるほど高くなった．果実の糖濃度と滴定酸度は，対照区が最も高かったが，NaCl濃度による差は認められなかった．12 mM区では各花房1番花のガクにチップバーンが多発し，平均果実重と総収量が他の3処理区より低くなった．8 mM区でも，チップバーン発生が増加する傾向にあったが，総収量は対照区とほぼ同等であったことから，NaClやその他のイオンを含む場合であっても，原水のECが8 mM区に相当する100mS/m程度までであれば，ピートバッグでイチゴ栽培に利用できる可能性が高いと考えられる．

培地の乾燥処理にともなうトルコギキョウ（Eustoma grandiflorum (Raf.) Shinn. ‘つくしの雪’）のロゼット化と日中の葉温上昇との関係について検討した．高温条件下（27-33℃）におけるロゼット株率は，土壌含水率を常に40％以上に保った対照区では0％となったのに対して，土壌含水率25％をかん水点として9週間管理した乾燥区では70％と高い値を示した．また，より高い温度条件下（29-35℃）ではわずか1週間の乾燥処理でもロゼット株率が高くなった．対照区の葉温と培地温は気温（30℃）とほぼ同じであったが，強日射時には乾燥区の葉温と培地温は約45℃に達した．以上の結果から，培地の乾燥によって生じる水ストレスは，強日射条件下で高温感応部位を含む植物体温を高めることによって高温条件下におけるトルコギキョウのロゼット化を助長するものと考えられた．

Changes in concentration and composition of anthocyanins during color development in fruit of strawberry (Fragaria×ananassa Duch.) were determined, using a pelargonidin 3-malonyl-glucoside (PMG)-producing cultivar 'Nyoho'. Color parameters of fruit appearance (L* : lightness, H° : hue angle and C* : chroma) reached their minimum (L* and H°) or maximum (C*) levels at 41 days after anthesis, while the concentration of total anthocyanins continued to increase. Anthocyanins may accumulate in the inner part of a receptacle at a later stage of fruit maturation. Anthocyanins may accumulate in the inner part of a receptacle at a later stage of fruit maturation. Although the relative percentage of cyanidin 3-glucoside (CG) was high at the early stage of color development, the percentage of PMG was relatively constant throughout coloring period. The occurrence or absence of PMG in strawberry cultivars can be determined readily. A further analysis was conducted to determine the occurrence of PMG in 20 Japanese cultivars. Pelargonidin 3-glucoside (PG) was the predominant pigment (66-94% of total anthocyanins), while PMG (5-24% of total anthocyanins) was detected in 11 cultivars. However, there was no significant difference in color parameters and the concentration of total anthocyanins between the groups of PMG-producing and -lacking cultivars. There were significant linear relationships between the concentration of total anthocyanins, and L* and H°, and also between the relative percentage of CG and L*. Within cultivars lacking PMG, there was a negative relationship between the relative percentage of PG and H°, but a positive one within cultivars producing PMG. Therefore, the occurrence or absence of PMG may play a negligible role in color development, but a balance of three major anthocyanins may affect color appearance of strawberries.

This experiment was conducted to clarify the effect of fertigation frequency (once or 8 times per day) on the growth, evapotranspiration rate, and photosynthetic and leaf morphological properties of chrysanthemum (Dendranthema grandiflorum Kitamura cv. Pinky) grown under different restricted root zone volumes (30, 100, and 300 ml). Shoot growth was reduced with decreased root zone volume, but, the growth reduction was smaller when the plants were fertigated 8 times per day rather than once per day. Although the evapotranspiration rate did not decrease when the plants were fertigated frequently, the rate decreased significantly when the total water consumption nearly equaled the water-holding capacity of the medium (50% of the volume), especially in 30-ml or 100-ml containers. Stomata size decreased with a decrease in fertigation frequency and container size. The percentage of open stomata (open/total stomata × 100) and consequently, transpiration rate, net photosynthetic rate, and leaf CO2 concentration were significantly lower in the plants grown in 30-ml and 100-ml containers, and fertigated once per day, compared to the four other treatments. The rates of photosynthesis and evapotranspiration of the plants fertigated 8 times per day remained faster than those fertigated only once per day. Consequently, vegetative growth of the plants fertigated frequently was equal to or more vigorous than those grown with three fold greater root zone volume but fertigated only once per day.

Two experiments were conducted to test the effects of reducing water and nutrient stresses on vegetative growth of chrysanthemum cv. Pinky in restricted root zone volume (10a1000ml). In Exp. 1, plants were grown using continuous flowing hydroponic system (CFHS). In Exp. 2, plants grown on a substrate were supplied nutrient solution via a drip system (SDS) 1, 3, 8 or 13 times per day until leaching occurred. In CFHS, stem length and node number were unaffected by root zone volume 25 days after planting (DAP). Total leaf area, shoot and root dry weights decreased with a decrease in root zone volume ; there were small differences among the plants grown in different containers, e.g. shoot dry weight of plants grown in 10 ml containers was about 80% of that in 1000 ml containers. Shoot to root ratio slightly increased with a decrease in root zone volume. In SDS, reduction in stem elongation was observed 14 DAP in plants grown in 30 ml containers fertigated only once a day. However, there was little difference in stem lengths among the plants grown in different containers 28 DAP when fertigated 8 times per day. Shoot growth 35 DAP was reduced with a decrease in root zone volume, however in plants grown in 30 ml or 100 ml containers, reduction of shoot growth markedly decreased with an increase in fertigation frequency. Root zone volume had a little effect on shoot growth if plants were fertigated 8 or 13 times. Irrespective of fertigation frequency, root dry weight increased with an increase in root zone volume. Shoot to root ratio was unaffected by root zone volume in plants fertigated 1 or 3 times but the ratio in plants treated 8 or 13 times increased with decrease in root zone volume. Thus, limiting of water and nutrients is the main factor in growth suppression caused by root zone restriction. Hence, vegetative growth of chrysanthemum plants in small container (≤100ml), e.g. cell or pot transplants production, can be sustained by the application of water and nutrients 8 times per day.

The effect of preharvest application of elevated CO2 throughout the fruit growing period on organic acid, sugar content, acid invertase activity (β-fructofuranoside fructohydrolase, EC 3.2.1.26), and color quality in tomato (Lycopersicon esculentum Mill. cv. Momotaro) fruit during storage at 20 °C was determined.The CO2-enriched tomato fruits contained significantly lower concentrations of citric, malic and oxalic acids, but had significantly higher reducing sugars and acid invertase activity at harvest and during storage. The concentration of these acids decreased with storage, whereas the activity of acid invertase and reducing sugar contents increased in the treated fruits; they were relatively constant in the control fruits. Furthermore, the elevated CO2 resulted in a deeper red color during storage.

Effect of nitrogen fertilization on flower development, especially on pistil differentiation and fruit malformation in 'Ai-Berry' strawberry, was investigated, using 5 rates of nitrogen application (0, 21, 42, 84 and 126 mg-N/plant•week) and 6 starting times of application at 84 mg-N/plant-week (1, 11, 21, 31 Oct., 10 and 20 Nov.).1. Except for the 0 mg-N treatment, the amount of N applied had little effect on the growth of flower bud based on the diameter. However, raising the rate of N application increased the number of rows of pistils in the primary flower; and it extended the duration of pistil differentiation between the base and the apex of receptacle. Furthermore, the mean diameter of ovaries of pistils on the apex of a receptacle decreased with respect to those on the base, so that the ratio of ovary diameters of pistils located on the apex and base of the receptacle (T/B ratio) also decreased. Plants supplied with high rates of N produced severely malformed fruits with undeveloped achenes on the distal region of receptacle.2. The effects of high N treatments were less if the treatments were delayed. Plants treated after petal differentiation started (21 and 31 Oct.) had fewer malformed fruits than those in which treatments were made earlier; those treated after pistil differentiation began (10 or 20 Nov.) had even fewer malformed fruits with less severe symptoms. Therefore, high N application before the onset of stamen differentiation may result in excessive numbers of malformed fruits.3. Although competition between fruits and the vegetative organs or between distal and proximal achenes for photosynthates may affect the occurrence of fruit malformation, the long duration for the complete differentiation of all pistils on the receptacle is probably the primary cause of the malformed fruits in plants supplied with high rates of N. Hence, to ameliorate this problem, we suggest that NO3-N content of petiole should be kept between 0.10 and 0.15% on dry weight basis during flower development, especially before pistils differentiate.

Differences in floral and fruit characteristics of strawberry (Fragaria×ananassa Duch.), were investigated, especially with respect to the relationship between the maturity of pistils at anthesis and the final fruit shape. The primary (first), secondary (third) and tertiary (5th) flowers on the single truss on six cultivars: Ai-Berry, Hokowase, Reiko, Toyonoka, Nyoho, and Morioka No. 16 were examined.1. The primary flower of 'Ai-Berry' had the largest number of rows of pistils from the base to the apex of the receptacle; the others had about the same number of rows of pistils. At anthesis, ovaries on the distal region of the receptacles were small and still immature; those of 'Hokowase' were intermediate in size, whereas the ovaries of the remaining 4 cultivars were large and mature. The ratio of ovary daimeter on the apex and base of receptacle (T/B ratio) was significantly smaller in 'Ai-Berry' when compared with the others. There were high correlations between fruit malformation due to poorly developed achenes on the distal end of the fruit with a) the number of rows of pistils; b) diameters of ovaries of pistils on the apex of receptacles at anthesis; and c) the T/B ratio.2. In 'Ai-Berry', there was a negative correlation between the number of rows of pistils and the diameter of the ovaries on the apex of receptacle. A similar correlation exist in 'Hokowase' which is the pollen parent of 'Ai-Berry'. Therefore, 'Ai-Berry' may have inherited the wide range of pistil maturity from the apex to the base of receptacles at anthesis from 'Hokowase'.

Changes in anatomy and receptivity of pistils of strawberry (Fragaria × ananassa Duch.) cv. Ai-Berry and Nyoho after anthesis were investigated.1. In the cymose truss of the 'Ai-Berry', the distal pistils of the primary (first) flower to open are small and immature, whereas proximal pistils near the base of the receptacle are fully mature and receptive to pollen. In some cases, the stigma of distal pistils are not receptive even 10 days after anthesis. Contrarily, on the tertiary (5th) flowers of 'Ai-Berry' and primary flower of 'Nyoho', the differences in size and the stage of development between the distal and proximal pistils are small and the pistils are equally receptive to pollen at anthesis.2. The number of undeveloped distal achenes on the fruit decreased if pollination was delayed in 'Ai-Berry', but the stigma on the basal pistils lost their receptivity 4 days after anthesis. Thus, on flowers pollinated 4 or more days after anthesis, the basal pistils failed to set seeds and developed poorly, giving rise to malformed fruits.3. Malformed fruits in 'Ai-Berry' may be reduced by controlling the timing and the duration of the pollination period, but this is difficult because of the wide range in pistil maturity from the apex to the base of the receptacle. To overcome this problem of malformation in 'Ai-Berry', cultural conditions which might narrow this range during flower development need investigation.

The duration of pistil differentiation and enlargement on the receptacle of primary flower buds of five strawberry cultivars were investigated to clarify the cause of malformation in 'Ai-Berry'. This clone produces fruits with immature achenes on the distal region of receptacle.1. 'Ai-Berry' had the largest number of rows of pistils between the base and apex of receptacles. The time interval between the onset of differentiation of the basal to the apical pistils was the longest compared to the other four cultivars. Except for the 'Hokowase', the rate of individual pistil differentiation was more rapid than it was in the other three cultivars. Hence, the duration for the complete differentiation of all pistils was the consequence of the large number of rows.2. Basal pistils of 'Ai-Berry' grew more rapidly than did those on the apex so that there was a large difference in ovary diameter and stage of development between them at anthesis. Moreover, the number of days from the end of pistil differentiaiton to anthesis was fewer than were those of the four other cultivars. Accordingly, fruit malformaiton in 'Ai-Berry' is a consequence of the pistils on the distal region of receptacle not being mature at anthesis so that they were probably not pollinated and did not set seeds.3. In 'Hokowase', the duration of pistil differentiation was shortest and the basal pistils compared to the distal ones grew most rapidly among the cultivars examined. Except for the 'Ai-Berry', the difference in ovary diameters between basal and distal pistils was greater in 'Hokowase' than in the other three cultivars.4. In contrast to 'Ai-Berry' and 'Hokowase', the apical pistils of 'Reiko', 'Toyonoka' and 'Nyoho' grew faster than did those on the base of receptacle. Hence, the difference in ovary diameters between them was not large at anthesis.

Four cultivars of melons (Cucumis melo L.) were harvested at different ages. Sugar content, the rate of CO2 and C2H4 evolution, and flesh firmness were measured.1. Fruits of var. reticulatus Naud. (‘Earl′s Favourite’ and ‘IW-57’) showed climacteric rise in respiration. ‘IW-57’ especially, showed extremely high rate of CO2 and C2H4 evolution. ‘Ginsen’ (var. acidulus Naud.) and ‘IW-57’ which can not be stored for a long time, showed higher respiration rates than ‘Hony Dew’ (var. inodorus Naud.) and ‘Earl′s Favourite’.2. Ethylene treatment (1, 000ppm, 20h) reduced flesh firmness. However, the effects were slight in ‘Ginsen’ and in the climacteric phase of ‘Earl′s Favourite’ and ‘IW-57’.3. Soluble solid contents (SSC) of ‘Honey Dew’ were high at the early stages of development and did not increase much at the period of 40 to 55 days after anthesis; sucrose content was relatively low at harvest even at the commercial harvesting stages. However, sucrose content increased after harvest, especially with ethylene treatment. In other cultivars, SSC and sucrose content increased rapidly just before the commercial harvesting stages. Fruit quality of ‘Earl′s Favourite’ decreased with the decrease of SSC and total sugar contents (TSC) after harvest.4. In ‘Honey Dew’ fruits, the relationship between SSC and TSC was low just after harvest but ethylene-treated fruits showed a high relationship. In other cultivars, the relationships between SSC and TSC were high. However, the values of SSC and TSC were not equal and SSC always showed relatively higher values than TSC.