著者

Geng Zhang Masahumi Johkan Masaaki Hohjo Satoru Tsukagoshi Toru Maruo

出版者

一般社団法人 園芸学会

雑誌

The Horticulture Journal (ISSN:21890102)

巻号頁・発行日

pp.OKD-008, (Released:2016-09-08)

被引用文献数

28

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Chronic kidney disease has become a major public health problem worldwide. The aim of this study was to investigate the differences in plant growth and photosynthesis among three lettuce (Lactuca sativa) types with different morphological characteristics under low potassium conditions, providing information for improving the method of low-potassium lettuce culture. Lettuce was hydroponically grown in half-strength Enshi formula nutrient solution containing 4, 2, or 1 me·L−1 K+. The plant yield and relative growth rates (RGR) of all three lettuce types were lowest under a treatment with 1 me·L−1 K+. In green leaf lettuce, reductions in both the net assimilate rate (NAR) and leaf area ratio (LAR) led to a decline in RGR. In Boston lettuce and romaine lettuce, the reduction of RGR was mainly due to a reduction in LAR, and to a lesser extent caused by NAR. Reduced potassium in the nutrient solution had a greater effect on mature leaves than on newly expanded leaves for all three lettuce types. In green leaf lettuce and Boston lettuce, photosynthetic rates of mature leaves significantly decreased under reduced potassium treatments, with a steady or gradually increased intercellular CO2 concentration; this indicated that non-stomatal factors suppressed photosynthesis. In romaine lettuce, the photosynthetic rate was less influenced by reduced potassium levels in the nutrient solution, and the significant increase observed in leaf mass per area might contribute to maintaining photosynthesis in the leaf. The decrease in photosynthesis in mature leaves exhibited a similar trend to the decreased potassium content in the leaves within the three lettuce types, but the factor related to the reduction of photosynthesis was different.

著者

Chengyao Jiang Masahumi Johkan Masaaki Hohjo Satoru Tsukagoshi Mitsuru Ebihara Akio Nakaminami Toru Maruo

出版者

一般社団法人 園芸学会

雑誌

The Horticulture Journal (ISSN:21890102)

巻号頁・発行日

pp.OKD-060, (Released:2017-04-18)

被引用文献数

5

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Tomato plants in greenhouse production are often confronted with light insufficiency in the lower canopy, especially in the winter low irradiation season. In this study, periodic alteration of plant density (PD) was proposed to improve the light environment of plants’ lower canopies, leaf photosynthesis, plant growth, and fruit development. These were investigated with winter cultivated tomatoes in a single-truss production system. Seedlings were transplanted to either movable or fixed cultivation benches for treatments with fixed PDs of 14.3 plants·m−2 (F14.3), and 10 plants·m−2 (F10), and unfixed PDs in a movable bench (MB; 25 plants·m−2 after transplanting to anthesis, 16.6 plants·m−2 at anthesis to initial fruit set, 12.5 plants·m−2 at fruit set to mature green, and 11.1 plants·m−2 at mature green to red-ripe). The leaf photosynthesis rates in MB and F10 were generally significantly higher than in F14.3. F14.3 had the tallest stems, but the lowest leaf area and shoot dry weight at end of experiment, while MB and F10 were not significantly different. MB had significantly the highest total yield, while the lowest data were observed in F10. The soluble solids content was increased in MB and F10 compared with F14.3, but no significant differences in ascorbic acid content or fruit hardness were observed among treatments. Therefore, a high PD in the vegetative stage, but a relatively lower PD in the fruit development stage, was highly efficient in intensive tomato cultivation.

著者

Masahumi Johkan Asami Nagatsuka Ayako Yoshitomi Takuya Nakagawa Toru Maruo Satoru Tsukagoshi Masa-aki Hohjo Na Lu Akio Nakaminami Kazuo Tsuchiya Yutaka Shinohara

出版者

園芸学会

雑誌

Journal of the Japanese Society for Horticultural Science (ISSN:18823351)

巻号頁・発行日

pp.CH-096, (Released:2014-05-03)

被引用文献数

1 12

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To produce tomato fruits with 6% average Brix without decreasing yield, we investigated the effect of moderate salinity stress on Brix and yield in a single-truss, high-density tomato production system. Because tomato fruit development can be predicted from cumulative temperature, we also assessed cumulative temperature after anthesis as a potential indicator for determining the starting points of salinity stress treatments. When transverse diameters of the first fruit reached 4 cm (i.e., early increase treatment) or the first fruits were at the mature green stage (i.e., late increase treatment), nutrient solution electrical conductivity was slowly increased until the breaker stage from 1.8 dS·m−1 to 6.0 dS·m−1. Plants subjected to the late increase treatment produced tomato fruits with Brix values of 6% without reductions in marketable yield. We also increased nutrient solution electrical conductivity based on cumulative temperature after anthesis and found that early-treated plants produced tomatoes with higher Brix levels and yields than late-treated plants. In summary, moderate salinity stress to avoid excessive stress on plants increased sugar concentrations without decreasing fruit yield and resulted in tomato fruits with average Brix of about 6% when nutrient solution electrical conductivity was increased at a rate of 0.1 dS·m−1·day−1. Because seasonal differences in cumulative temperature influence the appropriate timing of salinity stress applications, further study is needed to optimize year-round growth under moderate salinity stress in single truss, high-density tomato production systems.