Daytime temperatures in the greenhouse are often lower than the suitable growth temperature for forcing culture of tomato in Fukuoka. The effect of daytime heating on the marketable fruit yield during the winter season was investigated in this study. An increase of the minimum day temperature from 8°C to 20°C by a heater resulted in a significant increase of the number of marketable fruits, by improvement of the marketable fruit rates and intervals between anthesis and fruit ripening. In addition, fruit growth after flowering was accelerated when tomato plants were heated in the daytime. It was assumed that photosynthesis of the leaves accelerated, and translocation to fruit increased due to the rising air temperature. As a result, the marketable fruit yield on daytime heating was larger than in the control from April to May.
Blotching on the fruit surface, occurring due to the appearance of vascular bundles on the surface with low-level firmness, is an unfavorable character of tomato. The effect of the day temperature on the appearance of blotching on the fruit surface was investigated in this study. When tomato plants were cultivated in a phytotron with day temperatures of 20, 24, and 28°C under the same night temperature of 8°C, the degree of fruit blotching was severe under a day temperature of 20°C. The values of the blotching intensity decreased as the day temperature increased from 20 to 28°C. To apply the results to actual tomato production, tomato plants were grown in a greenhouse. An increase of the minimum day temperature from 8°C to 20°C with a heater led to a significant decrease of the appearance of blotching on the tomato fruit surface, and resulted in a thick fruit skin and high-level firmness.
Characteristics of tomato root for rootstocks were investigated by measuring average root diameter. The root diameter of the cultivar for rootstock became larger than that of scion cultivar at later growth stage. The root diameter was similar among the same line of rootstock cultivars and there was positive correlation between root diameter and tree vigor (R 2 =0.635). The information of root structure related root metabolism for high productivity will be more important in addition to disease and environmental stress resistance.
The effects of diurnal ventilation with a heat exchanger for dehumidifying were investigated to improve both the yield and quality of marketable tomato fruits grown in a greenhouse during winter. The heat exchanging ventilation based on the index of relative humidity lowered the temperature in the greenhouse. However, it ameliorated the inside conditions, such as decreasing humidity and reducing the period of dew condensation on the fruits. The concentration of carbon dioxide in the greenhouse remained higher than that of the control on cloudy days. Although the marketable yield from January to February decreased under the heat exchange ventilation, there was no significant difference in the total yield from January to May. In addition, the number of puffy fruits in March and April decreased, and total soluble solids from January to March were higher than those of tomato fruits cultivated in the control. Based on these results, it was revealed that tomato quality was improved compared with the control, while there was no significant difference in the total yield. Additionally it was suggested that the heat exchanging ventilation was effective as a dehumidifying technique for culture control.
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