In this study we investigated the effect of 5-aminolevulinic acid (ALA) on the in vitro regulation of protocorm-like bodies (PLBs) of Cymbidium spp. PLBs of Cymbidium species were explanted on modified Murashige and Skoog (MS) medium supplemented with various concentrations of ALA. In Cymbidium insigne, 1 mg L−1 ALA induced the highest PLB (100%) proliferation rate with an average of 7.9 PLBs/explant, whereas the control treatment had 1.6 PLBs/explant. The highest shoot formation rate (66.7%) and the highest number of shoots (1.3 shoots/explant) were observed at 0.1 mg L−1 ALA. In Cymbidium finlaysonianum, the highest PLB formation rate (100%) and the highest average number of PLBs of (7.4 PLBs/explant) were observed for explants cultured on medium supplemented with 0.01 mg L−1 ALA. The highest number of shoots (0.7 shoots/explants) with a shoot proliferation rate of 33% was observed on medium supplemented with 0.1 mg L−1 ALA. The results of this study suggest that a low concentration of ALA can induce PLB and shoot formation and that ALA can serve as a novel additive for plant tissue culture acting as a growth regulator for Cymbidium micropropagation.
For the cultivation of tomatoes with high soluble solids content, the root system was split vertically and irrigation to the upper part of the root system was stopped to create split vertically (SR treatment), while the irrigation amount per plant was maintained to the lower part at the same level as that of a non-stress treatment (Control). In Experiment 1, the soluble solids content in the SR treatment (1.3 Brix %) was significantly higher than that of the Control. However, there were no differences in plant growth and fruit quality between the SR treatment and the treatment in which the amount of water supplied was half of that of the Control. These results indicated that tomatoes with high soluble solids content in the SR treatment were cultivated without reducing the irrigation amount compared to that of the Control. In Experiment 2, the difference in the volume of the root zone in the lower container in the SR treatment affected the fresh weight per fruit and soluble solids content when sand was used in the lower container. However, when Andosol was used in the lower container, the difference in the volume of the root zone did not affect the yield and soluble solids content of the tomatoes.
The effects of modified atmosphere (MA) and 1-methylcyclopropene (1-MCP) on the quality and longevity of florets were investigated in potted carnation ‘Scarlet’. MA with and without 1 μL·L−1 1-MCP (2 day-exposure) for whole plant at 22/17°C significantly delayed the peak of ethylene and wilting of florets, and prolonged the display life from 7.0 to 9.4 days after harvest (DAH). In the experiment for cut florets, active MA (a-MA; initial gas, 2.75% for CO2 and 11.5% for O2) for 2 days prolonged the longevity from 5.5 to 7.8 days, whereas a-MA in combination with the 1-MCP (a-MA/MCP) treatments prolonged longevity to 12.5 days. Maximum ethylene production was decreased from 58.3 to 9.8 nL·g−1·h−1 by a-MA, while only trace amounts was detected in a-MA/MCP. In the gynoecium, a-MA repressed DcACS2 (1-aminocyclopropene-1-carboxylate synthase) expression throughout the experiment and DcACS3 until 4 DAH. The a-MA also repressed DcACO1 (ACC oxidase) until 6 DAH, whereas a-MA/MCP completely repressed DcACO1. In the petals, a-MA/MCP repressed DcACS2 and DcACS3. The both treatments significantly lowered respiration rate of florets on 8 DAH, and increased contents of soluble carbohydrates in petals on 4 DAH. These results indicate the combination of MA and 1-MCP is more effective than MA alone in the reduction of ethylene production, respiration and the expressions of DcACS2 and DcACO1, and maintained soluble carbohydrates, and thus improved postharvest qualities compared to the single treatments.
Tomato plants were grown using a rockwool-based drip culture, and the nitrous oxide (N 2O) emission from the rhizosphere was precisely observed using an automatic monitoring system. Fertilization was intermittently conducted four times daily for 1 h each time (the standard conditions). Basically, N 2O emissions were very quick and exact responses against the fertilization. Under the standard conditions, N 2O emissions started within 30 min and peaked within 90 min from the beginning of each fertilization, and more than 90% of all emissions occurred within the 2 h following fertilization. The number of peaks and duration for N 2O emissions altered synchronously with the fertilization. On the other hand, the maximum rate and the total amount of N 2O emissions did not always reflect the fertilization quantity. For example, halving the concentration of the fertilizing solution decreased both the maximum rate and total amount of N 2O emissions to approximately one-fifth of that observed under the standard conditions. The observed N 2O emissions varied 1.0–4.6% of applied nitrogen among three trials under the standard conditions. It is possible that another factor, such as crop size and vigor, affect the emission. The monitoring would allow us to know the optimum timing and quantity of fertilization.
The purpose of this study was to investigate the individual and combined effects of low O2 and high CO2 on chilling injury (CI) alleviation in cucumber fruit. Fruits were stored at 5°C for 5 days under 4 different gas compositions: (1) low O2; (2) low O2 with high CO2; (3) high CO2 and (4) ambient air as control. After storage at 5°C, all fruits were transferred to ambient air at 24.5°C for 6 days to evaluate the progress of CI. The weight loss of fruits stored at ambient air was higher than those stored at the controlled atmospheres. Change in skin color was suppressed in fruits stored under low O2. Increased electrolyte leakage and malondialdehyde (MDA) equivalent were suppressed by storage at low O2 compared with low O2 with high CO2. These results suggested that low O2 acted as a dominant factor for alleviating CI of cucumber fruits, while, the combination with high CO2 did not induce synergistic effects, but it gave negative influences.
Low sugar content of fruits in winter, and blossom end rot in summer, are serious problems in the production of tomato with high soluble solids content. In the present study, we investigated the effects of the rare sugars D-psicose and D-tagatose on the sugar content of fruits and incidence of blossom end rot during several cropping seasons. We determined a highly positive correlation between the sugar content and the cumulative solar radiation during the maturation period. Treatment with D-psicose resulted in an increase in the sugar content over every cropping season. It resulted in a reduction in the incidence of blossom end rot, a reduction in stomatal conductance, and an increase in the relative water content in summer. On the other hand, it resulted in an increase in the incidence of blossom end rot in winter and rainy season. Treatment with D-tagatose had no effect on the sugar content, incidence of blossom end rot, water potential, stomatal conductance, or relative water content. Our results indicate that treatment with D-psicose is advantageous for increasing the sugar content in winter and preventing the incidence of blossom end rot in summer.
In this study, we discussed how temperature and other environmental factors affect the fruit growth and quality of Satsuma mandarin grown in a plastic house with heating. At 14–23°C, the average nighttime air temperature was positively correlated with the standardized fruit growth rate (GRFSt) in the young stage. In contrast, GRFSt was clearly depressed with a daytime air temperature at around 30°C, and the optimum air temperature for active fruit growth was 25°C. Moreover, in the middle and mature stages, the air temperature did not correlate with the GRFSt. These results indicate that, in the young stage, the air temperature should be controlled at around 25°C during the daytime and 20–23°C during the nighttime for active fruit growth. In the middle and mature stages, fruit growth might not require nighttime air temperatures that are as high as 20–23°C. The air temperatures did not correlate with the fruit soluble sugar content (SSC); in contrast, a close relationship was found between the predawn xylem water potential (ΨXy) and SSC. The day temperature, radiation and ΨXy were linearly correlated with the fruit titratable acidity (TA) in the young stage.
In order to clarify the effect of nighttime temperatures on fruit development of Satsuma mandarin, we examined the fruit water and carbon balances using the 13C tracer method and the roles of phloem and xylem transports for fruit growth under moderate night temperatures (MN, set at 23°C) and low night temperatures (LN, set at 13°C). The average predawn xylem water potentials were −0.79±0.04 MPa under MN and −0.77±0.03 MPa under LN. Fruit growth used 86% of pedicel sap flux toward the fruit, while transpiratory water losses from the fruit surface were 14% of pedicel sap flux under both MN and LN. The daytime integrated xylem sap flux was negative, but it was positive in the nighttime. The integrated phloem sap flux (ΣJPhlo) and the difference in ΣJPhlo between MN and LN were only 6–10% and 4% of the total sap accumulated in the fruit, respectively. Integrated fruit photosynthesis and integrated CO2 efflux from the fruit surface were 7–8% and 22–23% of the total carbon supply toward the fruit, respectively. This indicates that carbon translocation from leaves to fruit via the phloem of the stem is the main source of carbon for the fruit.
In order to control nighttime temperatures with energy saving, how different night temperature regimes affected on the fruit growth, quality and13C allocation from leaf to fruit were researched by both the partial heating and whole tree heating. One type, altering time of nighttime heating, the end of day (EOD) -heating, middle of night (MON) -heating, and predawn (Pd) -heating were applied. The EOD-heating temporally activated the fruit growth and accelerated the13C allocation from leaf to fruit through short term (hours) researches by the partial heating, however, comparing to the conventional heating as 20°C constant in nighttime by the whole tree heating during 60–90 days after full bloom (DAFB), no superiority was observed in both the fruit volume increase and fruit quality, and the MON-heating showed the depression of fruit growth. Another type of a regime determined by daily integrated solar radiation, comparing to the conventional heating as 17°C constant in nighttime during 78–120 DAFB, no superiority was observed in the fruit quality. Nighttime13C allocation from the leaf to fruit was detected at 90 DAFB, though was hardly detected at all at 120 DAFB regardless of night temperatures as high as 25°C at both days.
An estimation based on a mathematical model to predict hourly evapotranspiration (ET) rates that occur inside a plant factory system was made using the Stanghellini model. The Stanghellini model is considered more appropriate for estimating the rate of ET inside the soilless culture of greenhouse tomatoes. The model requires some climatic data (e.g., solar radiation, air temperature, relative humidity, and wind speed) and plant growth parameters (leaf area index) as inputs. In this study, the observed data were obtained from an experimental greenhouse located at the Ehime University, Japan. The ET rate of tomato (Lycopersicon esculentum Mill.) crop was measured using a weighing method. Accurate determination of ET is essential to precisely compute crop water use and to assist growers for applying good irrigation management. The results showed that solar radiation and vapor pressure deficit are important factors driving the ET rate. The model's output showed good results for determining the ET rate and depicted crop water requirements on an hourly basis.
Among various environmental factors, the effects of light quality and quantity on growth of vegetables and ornamental plants were investigated thoroughly in closed plant factories, whereas how solutes and minerals in hydroponics affect on growth of vegetables were poorly understood. In this study, we investigated the effects of salinity and nutrients on the growth of red leaf lettuce (Lactuca sativa L. cv. Mother-red). A closed plant factory with hydroponic cultures supplemented with sodium salt (NaCl) or seawater was employed for cultivation of lettuce. The fresh weight of lettuce grown in culture with NaCl was dramatically reduced when compared to those grown in standard culture or culture with seawater. The lettuces grown in the culture with NaCl or seawater contained higher amounts of sugar and anthocyanin, and the lettuce plants grown in the culture with seawater accumulated highest levels of photosynthetic pigments, chlorophylls and carotenoids. These results indicate that the addition of some solutes (e.g. NaCl) to the culture medium affect the size of plant as well as the levels of sugars and pigments in the plant, and suggest that the addition of seawater (20%) to the medium is effective to produce lettuces with higher quality and nutritional value.
Three alloplasmic lines were established by combining the nucleus of Brassica rapa with the cytoplasm of Diplotaxis muralis. Two alloplasmic lines showing complete male sterile (MS) phenotypes were designated as MS-Yukina and MS-Kabu, whereas one alloplasmic line that releases some pollen grains was designated as partial male sterile (PMS)-Hakusai. To investigate differences in the MS phenotypes, relationship between the length of flower buds and development of young pollen grains was analysed. The length of flower buds containing pollen at the meiosis stage was 1.90-fold (in MS-Yukina), 1.31-fold (in MS-Kabu), and 1.27-fold (in PMS-Hakusai) that of the corresponding maintainer line (N-Yukina, N-Kabu, N-Hakusai). This value was 1.74-fold (in MS-Yukina), 1.48-fold (in MS-Kabu), and 1.22-fold (in PMS-Hakusai) that of D. muralis. These results indicate that the meiosis stage is delayed in all alloplasmic lines compared to their maintainer lines or their cytoplasmic donor. The delay in the meiosis stage was the least pronounced in PMS-Hakusai among the three alloplasmic lines examined. Thus, a positive correlation might exist between the delay of the meiosis stage of pollen development and the degree of male sterility in these alloplasmic lines. Delayed meiosis in pollen might contribute to male sterility in the three alloplasmic lines.