This study aims at establishing a relationship between water supply and CO₂ concentration in the rootzone, and to identify disturbing factors using data-driven modelling. In our previous study, 10 longan trees were planted in split-root technique and kept under controlled conditions. During six months, 5 trees were partially irrigated on one side of the root system, while the other side was kept non-irrigated. The sides were switched in a two-week interval. Five control trees received full irrigation on both sides. Monitoring results on CO₂ concentration in the rootzone, soil moisture and stomatal conductance indicated a weak correlation between the CO₂ concentration in the rootzone and the soil moisture, but without a statistically significant correlation, partially because air temperature was a main disturbing factor. In this study, Random Forests was applied to establish a CO₂-water stress relationship based on air temperature, relative humidity, vapour pressure deficit and soil moisture. It was shown that the most important factor on CO₂ concentration in the rootzone was soil moisture, followed by air temperature. Together with the information retrieved, the results suggest a potential of CO₂ monitoring in the rootzone for assessing plant water status continuously and with a minimum level of invasion.

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Mango is a widely cultivated tropical fruit crop and exhibits climacteric behavior characterized by changes in respiration and ethylene production during development and ripening. Optimal postharvest ripening depends on many factors, but during shipping to distant high-value markets, ripening generally should be minimized. Monitoring the physiological activity presents possibilities for real-time response and the integration of smart technologies. However, systems are still needed which are portable, economical, and accurate. Optical sensors are low-cost but lack good accuracy, while electrochemical sensors are highly accurate but expensive. Economic nanoparticle sensors are being developed for potential applications in fruit quality monitoring, but they can be complex. This work explores possibilities for development of a monitoring system for climacteric fruits such as mango and presents results on testing of commercially available systems and development of sensors that will fit the criteria.

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This study investigated the effects of the storage conditions, namely temperature and relative humidity on the quality of fresh mango fruit (Mangifera indica L. ‘Nam Dokmai’) before and after distribution from Thailand to Japan. Fruit samples were harvested from two commercial orchards in Phrao and Phitsanulok, Thailand, and stored immediately after harvest and after distribution for 4–6 d respectively at 15, 25 and 35°C. The contents of L-ascorbic acid (L-AsA), sugar components and total soluble solids (TSS), as well as hardness score and peel colour of fruit samples were measured as a fruit quality indicator. As a result, fruit samples from Pitsanulok attained a better storage condition sooner than Phrao samples because of shorter distance to the packing house in Bangkok. Despite of the similar hardness score, the total sugar contents and L-AsA contents at harvest was significantly higher for Phrao than Phitsanulok. Total sugar contents and TSS in the after-harvest experiment indicated postharvest ripening for which the storage temperature of 25°C was found to be optimal. In the after-distribution experiment, fruit quality parameters showed temperature-dependent responses of mango fruit. Further study is needed for an improved export system considering actual storage temperature of fresh mango fruit.

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Thailand is one of the world’s highest producers of mango, the majority of which are exported to Japan via long supply chains. The mango is a climacteric fruit that ripens after harvest. Therefore, it is very important to treat immature fruits appropriately during lengthy distribution period which can takes approximately three weeks from Thailand to Japan by shipping. The present study aimed to determine the effects of postharvest distribution and storage temperature on physiological changes in fresh mango fruits (Mangifera indica L. ‘Nam Dok Mai’) imported from Thailand to Japan. Immature mango fruits were utilized that were transported immediately after harvest from Thailand by air, and were then stored in the actual distribution temperature conditions of shipping for 3 weeks and also heated to 25°C for 16–18 d in the laboratory. Postharvest ripening of immature mango fruits was observed as changes in fruit firmness, peel color, and sugar content under the storage conditions. Softening and coloring were induced during postharvest storage, especially in the first 4 d. After the first 4 d of maturation enhancement, the change in maturation level remained small.

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This study investigated the effect of the red (R) to far-red (FR) photon flux density ratio on the growth and crocin yields of 64 saffron (Crocus sativus L.) corms that were hydroponically cultivated in closed chambers. The life cycle of saffron can be divided into four stages: formation of the flower buds, flowering, formation of the daughter corms (FD) and development of the daughter corms (DD). During the DD stage, the saffron corms were cultivated under the same environmental conditions except for the light quality, which was applied at an R/FR ratio of 15.8 (FL treatment) or 1.8 (FR treatment). There was no significant difference between treatments in the shoot length, or the maximum diameter, weight and stigma weight of the daughter corms. However, there was a significant difference in the absorbance of crocin solutions. Although the cause of FR-induced increase in crocin was not elucidated, it was presumed that a low R/FR ratio during the DD stage accelerates the translocation of photosynthetic products from the leaves to the corms to generate carbohydrate-enriched corms. This might result from increased sink strength, which is associated with phytochrome equilibrium.

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The effect of temperature on changes in raffinose family oligosaccharides (RFOs) and isoflavones contents during cultivation period of soybean sprouts was investigated to enrich the basic knowledge on the production method of soybean sprout with high functionality. In this experiment, soybean sprouts were cultivated at 10°C, 15°C, 20°C, 25°C, or 30°C, concurrently respiration rate was measured by the flow-through method using gas chromatography. RFOs such as raffinose and stachyose, and isoflavones were then determined using high performance liquid chromatography. The amount of RFOs was found significantly dependent on cultivation temperature and decreased rapidly at higher temperature. The degradation of RFOs increased remarkably at germination preparation phase and then decreased gradually during radicle elongation phase under all temperature conditions. The purpose of RFOs degradation in growing soybean sprouts during each phase was different. Additionally, the highest amount of remained RFOs was observed in soybean sprouts cultivated at 20°C. In the case of isoflavones, there was no significant difference of total isoflavone glycosides observed among cultivation temperatures. Our results suggest that optimization of the cultivation temperature and the hypocotyl length of the sprouts at harvesting time influence the amount of beneficial RFOs and isoflavones in soybean sprouts.

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The phase of the circadian clock (body time) is related to various aspects of physiology and metabolism in plants. Therefore, it is important to evaluate body time to control plant quality and growth. The molecular timetable method, a statistical analysis of the transcriptome, is useful for plant body time estimation. However, it is necessary to verify some assumptions in this method for high resolution estimation in plants under various conditions. To investigate whether the assumptions are valid, we analyzed the period length and expression pattern of genes. We used Arabidopsis thaliana as a model plant, and both lettuce and tomato as model crops. A. thaliana and lettuce were cultivated under conditions of constant light in a closed plant factory, and tomato was cultivated in a sunlight-type plant factory. We found that estimation of the period length of the plant circadian rhythm was possible and that the gene expression pattern correlates well with test-fit cosine curves. Thus, we successfully demonstrated high-resolution estimation of body time in plants using a molecular timetable method.

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The aim of this study was to clarify how the air temperatures during the light and dark periods affect growth and biosynthesis of the iridoid glycoside asperuloside in Hedyotis diffusa. Ten experimental air temperature treatments were established in a growth chamber during the cultivation period: (light/dark period air temperature) 30/15°C, 20/20°C, 25/20°C, 30/20°C, 35/20°C, 25/25°C, 30/25°C, 35/25°C, 40/25°C and 30/30°C. It was found that the stem length and epigeous dry weight were greatest with the 35/25°C treatment, whereas the leaves near the apical buds of the branches became blackened with the 40/25°C treatment, indicating that 35°C represents the upper air temperature limit during the light period for growth without any physiological disorder. By contrast, the asperuloside concentration was high with an air temperature of 25°C or less during the light period and 20°C or less during the dark period, and was greatest with the 25/20°C and 30/20°C treatments. Thus, air temperatures of 25–30°C during the light period and 20°C during the dark period are effective for maximising the asperuloside content in H. diffusa.

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Eleocharis vivipara is an amphibious sedge that displays C₄ traits under terrestrial environments and C₃ traits in submerged environments. This plant is thus potentially advantageous for screening genes indispensable to the development of C₄ photosynthesis. In this study, we performed de novo transcriptome analysis of E. vivipara using its terrestrial- and submerged-type plants. By next-generation sequencing (NGS), approximately 90 and 89 million reads were yielded for the terrestrial and submerged types, respectively, and were assembled into 27,249 unigenes. Of these de novo consensus sequences, 94.5% showed similarities to database-registered sequences, and 69.4% were assigned with Gene Ontology terms. Our de novo assembled sequence data should provide a foundation for genetic analysis of the C₄ photosynthetic system.

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The rising concentration of atmospheric carbon dioxide (CO₂) is known to directly affect plants, increasing growth, yield, and resource use efficiency. Further, research has shown that sweetpotatoes (Ipomoea batatas) represent a potential source for bioethanol production, particularly industrial cultivars bred specifically for this purpose. However, the effects of elevated CO₂ on these new industrial cultivars of sweetpotato remain uninvestigated. We grew industrial cultivar CX-1 sweetpotato plants in open top field chambers exposed to either ambient or elevated (ambient+200 μmol mol⁻¹) CO₂ for one growing season and examined growth and allocation responses. Growth in elevated CO₂ increased biomass production for cultivar CX-1. In particular, total storage root dry weight increased by 40.9% compared to plants grown in ambient CO₂. Fresh weight allocation to belowground plant organs (fine roots and storage roots) also increased under elevated CO₂, but dry weight partitioning was unaffected. Aboveground (vines plus leaves) dry weight: fresh weight ratio was increased by elevated CO₂, indicating possible alterations in tissue anatomy and/or chemistry. Our findings indicate that the industrial sweetpotato cultivar CX-1 has potential as a source for bioethanol production, and this potential could be enhanced as atmospheric CO₂ continues to rise.

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