Energy-Saving Night Temperature Regime for Satsuma Mandarins (Citrus unshiu Marc.) Grown in a Plastic House with Heating. I. Effect of Temperature and Water Condition on Fruit Growth and Quality

Abstract

In this study, we discussed how temperature and other environmental factors affect the fruit growth and quality of Satsuma mandarin grown in a plastic house with heating. At 14 23°C, the average nighttime air temperature was positively correlated with the standardized fruit growth rate (GRFSt) in the young stage. In contrast, GRFSt was clearly depressed with a daytime air temperature at around 30°C, and the optimum air temperature for active fruit growth was 25°C. Moreover, in the middle and mature stages, the air temperature did not correlate with the GRFSt. These results indicate that, in the young stage, the air temperature should be controlled at around 25°C during the daytime and 20 23°C during the nighttime for active fruit growth. In the middle and mature stages, fruit growth might not require nighttime air temperatures that are as high as 20 23°C. The air temperatures did not correlate with the fruit soluble sugar content (SSC); in contrast, a close relationship was found between the predawn xylem water potential (Xy) and SSC. The day temperature, radiation and Xy were linearly correlated with the fruit titratable acidity (TA) in the young stage.

Energy-Saving Night Temperature Regime for Satsuma Mandarins (Citrus unshiu Marc.) Grown in a Plastic House with Heating. II. Effect of Night Temperature on Fruit Water and Carbon Balances

“…Similar results were obtained in the fruit quality except fruit rind color and fruit yield (Table 3). These results were not inconsistent with our previous study, where no significant correlation was observed among nighttime temperatures during 60 120 DAFB and fruit soluble sugar content and titratable acidity at 180 DAFB (Yano et al, 2014).…”

“…To clarify the water and carbon balances of each fruit during active fruit growth, four repeated short-term studies were conducted at 60, 71, 100, and 120 DAFB. The days were at the cell enlargement period as stage II (Kikuchi et al, 1964), and at young and middle stages (Yano et al, 2014). Figure 1 shows the average air temperature (Ta) and…”

Energy-Saving Night Temperature Regime for Satsuma Mandarins (Citrus unshiu Marc.) Grown in a Plastic House with Heating. III. Application of Different Night Temperature Patterns

“…In addition, the delayed decrease in the juice-acid content is accompanied by a depression in fruit volume enlargement (Kurihara, 1969(Kurihara, , 1971Utsunomiya et al, 1982;Inoue and Chien, 1988). In Satsuma mandarins grown in a plastic house with heating which is harvested fruit at summer, the nighttime air temperature was considered to be within the suitable range for fruit growth (20 25°C) at stage III (Yano et al, 2014). In this case, fruit with excessive acid content is rarely produced as long as water is managed precisely.…”

“…A possible energy-saving temperature regime for Satsuma mandarins grown in a plastic house with heating has been developed. Firstly, at 60 90 DAFB, it is necessary to control 25°C in the daytime (Yano et al, 2014) and not to be lower than 20°C at night (Fig. 4E).…”

“…Former studies have shown that high-quality fruit production in Satsuma mandarin is based on adequate temperature control, specifically maintaining the temperature between 20 and 25°C during the pre-harvest growth period (Kurihara, 1969(Kurihara, , 1971Utsunomiya et al, 1982;Inoue and Chien, 1988). In the early stage of fruit growth, Satsuma mandarins grown in a plastic house with heating should be grown in temperatures maintained around 25°C in the daytime and 20 23°C at night for active fruit growth (Yano et al, 2014). In addition, for the production of commercially attractive fruits of desired color, the temperature should not be lower than 16 17°C to enable the generation of carotenoids in the fruits' rind.…”