a b s t r a c tHigher relative humidity under elevated CO 2 conditions increases stomatal conductance and is expected to promote photosynthesis and growth of tomato. However, yield increase under higher relative humidity has been often reported to be unstable, depending on the growing conditions. Therefore, we investigated the effect of relative humidity and nutrient supply on growth and nutrient uptake under elevated CO 2 conditions in greenhouse tomato production. In two greenhouses, we grew tomato hydroponically at two electrical conductivity (EC) levels (low EC treatments: 0.8-1.2 dS m −1 , high EC treatments: 1.6-1.9 dS m −1 ). In one greenhouse, we installed a humidification system. The other was designated as a control. The dry weight (DW) per plant tended to increase with humidification though without significant differences. The leaf area per plant was not affected by humidification, but the high EC treatment increased the leaf area. The average water uptake in the low EC with mist decreased compared with that without mist. Our results suggested that water use efficiency was increased by higher humidity, whereas the nutrient content of leaves was suppressed by mist in the low EC. In both the treatments, supplying higher EC levels of nutrient solutions increased N, K and P contents but did not increased Ca or Mg contents as well as in low EC without mist. These results suggest that supplying high EC nutrient solutions cannot increase Ca and Mg contents sufficiently in leaves and stems. To stably increase yield of tomato by humidification under elevated CO 2 conditions, it is important to monitor the transpiration rate and carefully control relative humidity.
This paper proposes an innovative CO 2 enrichment system for crop production under a controlled greenhouse environment by means of tetra-n-butylammonium bromide (TBAB) + CO 2 semi-clathrate hydrate (SC). In this system, CO 2 is captured directly from exhaust gas from a combustion heater at night, which can be used for stimulating photosynthesis of crops in greenhouses during daytime. Although the gas capacity of TBAB + CO 2 SC is less than that of CO 2 gas hydrate, it is shown that TBAB + CO 2 SC can store CO 2 for CO 2 enrichment in crop production even under moderate pressure conditions (<1.0 MPa) at 283 K.
One of the direct approaches for obtaining a high yield of strawberries is high-density cultivation. Such cultivation improves the efficiency of space utilization in a greenhouse; however, it requires the movement of planting benches. The aim of this study is to develop a circulating-type movable bench system for strawberry cultivation that realizes high-density cultivation and improves work efficiency. The developed system, which is 16.0 m long and 9.2 m wide, consists mainly of two longitudinal conveying units, two lateral conveying units, two nutrient supply units, a chemical sprayer, 62 planting benches, and a control unit. The design of the longitudinal conveying mechanism combining the rotating and sliding movements of rods for pulling the benches and a method of controlling the conveying units achieves effective circulation, resulting in a cycle time of 67.0 s during which the successive bench reaches the initial position. This cycle time could be shortened by increasing the speed of lateral conveying. The planting density obtained using this approach is 16.0 to 20.0 plants m -2 , which is roughly 2 to 2.5 times the plant density obtained in the conventional method of cultivation. Furthermore, the four cultivars used in this study showed vigorous growth, and the cultivars Akihime and Moikko showed a marketable yield twice as high as the conventional yield.
The effects of pinching and lowering on cucumber yield and yield components were investigated. A short-term experiment was conducted on 3 cucumber (Cucumis sativus L.) cultivars grown hydroponically in a greenhouse from July to October 2011. Pinching plants were pinched at above 20 leaves on a main branch and at the 2nd leaf on the first lateral branches. Lowering plants were pinched at above 15-19 leaves on a main branch and not pinched on 4 lateral branches that were lowered with their growth. The fresh fruit yield of pinching plants in all cultivars was higher than in lowering plants. The high fresh fruit yield was caused by the high dry weight yield, and the high dry weight yield was caused by the high dry matter production and distribution of it to fruits. Total dry matter production was correlated with light interception at 40 days after transplanting, but was correlated with light use efficiency, i.e., dry matter production per intercepted light, during the entire experimental period.Key Words:dry matter distribution, dry matter production, leaf area index, light interception, plant factory
Conditions d'exposition professionnelle des secrétaires d'une entreprise du secteur privé aux douleurs du rachis et des membres supérieurs à Abidjan, Côte d'Ivoire Pain of the spine and upper limbs related to occupational exposure conditions of secretaries in a private sector company in Abidjan, Ivory CoastObjective. To contribute to the improvement of secretaries working conditions. Materials and methods. The study was cross-sectional and descriptive of the working conditions of the service secretaries for at least 1 year of a private sector company in Abidjan. A questionnaire was administered to the secretaries present during the investigation. They were also observed in the workplace. Results. The study included 48 female secretaries, with an average age of 45 AE 8.08 years, mostly overweight or obese (66.7%); 56.25% of the secretaries had more than 10 years of the post; 93.7% of them did not have ergonomic seat. Pain was the main symptom (79.2%). The cervical spine (60.4%) and the thoracolumbar spine (58.3%) were more affected than the shoulders (39.6%). Among the surveyed secretaries, 87.3% (42/48) had not received any training in working gestures or postures. There was a predominance of lesions involving the secretaries following factors: overweight or obesity (90.6%), the position of seniority over 10 years (56.2%), poor working posture (89.7%) and use of non-ergonomic seat (93.7%). Conclusion. Secretaries working conditions are binding. They can be improved by processing workstations, training for secretaries to work postures and gestures, the respect of labor standards on visual display terminal and the appropriate health surveillance. ß
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