Yuta Miyoshi

Night-time leaf wetting process and its effect on the morning humidity gradient as a driving force of transpirational water loss in a semi-arid cornfield

Abstract Night-time leaf wetting process was analyzed in relation to micrometeorological conditions in a semi-arid cornfield and its effect was examined in the following morning with reference to the leaf-to-air humidity gradient which is a driving force in transpiration. Leaf wetness occurred due to dew formation under clear and calm night conditions which decreased canopy surface temperature to the air dew-point temperature. The amount of dew on leaves collected around sunrise (06:00) was 26.4-104.3 g m−2 · leaf area, which corresponded to 0.07-0.27 mm water. Leaf wetness remained until around 10:00 and significantly decreased leaf temperature. As a result, the leaf-to-air humidity gradient also decreased in the wetted leaf compared to the non-wetted leaf. These results suggest that night-time leaf wetting induces lower transpiration rate and may play a role in diminishing plant water stress due to excess transpirational water loss in the morning in semi-arid environments. Further studies are needed in order to demonstrate this possible effect.

Approach to local environment control for stable production of strawberry

Abstract In a farmers strawberry greenhouse, seasonal changes in solar radiation and air conditions (temperature, humidity and CO 2 concentration) were measured, and it became clear that the stable year-round production of strawberry was depressed by low temperature and low solar radiation in the cold season and excessively high daytime temperature in the warm season. Furthermore, dew formation in the nighttime, excessively low humidity in the fair daytime and the inappropriate application of CO 2 enrichment were also concerned with the depression of stable production. Therefore, a local environment control system was newly developed on the basis of the air circulation and the heat exchange between the constant soil temperature layer and strawberry inter-rows. The system was composed of an underground air pipe (UAP) and inter-row air ducts (IAD) connected to UAP, and UAP was set at a depth of 1.5m where the soil temperature is kept around a temperature suitable for the strawberry growth all the year round. The system can be expected to enable the energy-saving and local control of the ambient air condition of strawberry crops for the stable year-round production.

Investigation of supplemental lighting with different light source for high yield of strawberry

Abstract Although supplemental lighting has been successfully used to boost greenhouse vegetable production, it has not found wide application in forced strawberry cultivation. In this study, we examined the effect of supplemental lighting from two different light sources on strawberry growth and yield. Strawberry plants were exposed to LED or fluorescent lamp illumination for 12 hours (6:00-18:00) daily from January to April. Under LED illumination, PPFD values greater than 400 μmol m-2 s-1 were recorded at leaf heights of 10-30 cm, and leaf photosynthetic rates in plants exposed to LED supplemental lighting were much higher than in controls and plants exposed to fluorescent light. This accelerated photosynthesis promoted plant growth, as manifested by increases in leaf dry weight, leaf area, and specific leaf weight, leading in turn to significant increases in average fruit weight, number of fruits, and marketable yield. The higher yields observed in LED-exposed plants compared with those under fluorescent lamp illumination were due to comparatively higher LED light intensities. These results suggest that supplemental lighting using higher irradiance LED is an effective method for high yield production during forced strawberry cultivation.