Horticultural Science and TechnologyISSN:1226-8763(Print) 2465-8588(Online)원예과학기술지

This study was conducted to investigate the differences in internal environmental factors, photosynthetic factors, and increment of fruit volume according to direction of the greenhouse grown watermelon (Citrulls lanatus). The greenhouse was single-span type, and the directions were east-west (EW) and southeast-northwest (SENW). During research period, daily average intensity of solar radiation (ISR), air temperature, and air temperature in daytime were all significantly higher in SENW than in the EW. The solar radiation intensity in the SENW from sunrise to about 13:00 was maintained higher than in EW greenhouse, and accordingly, daily integrated solar radiation was maintained high during the research period. In near plant leaves on fruiting part at around 11 am, ISR in the SENW was twice as high as 408.13 µmol·m^-2·s^-1 in EW. And transpiration rate was 6.53 mmol·m^-2·s^-1 in the SENW greenhouse. It was significantly higher than 4.75 mmol·m^-2·s^-1 in EW. The difference between leaf temperature and air temperature values (DV) was significantly higher in EW than in SENW. Leaf temperature and DV showed a high correlation with vapor pressure deficit (R = 0.904**, 0.799*), and ISR showed a high correlation with transpiration rate (R = 0.856**). And ISR affected leaf temperature, and leaf temperature affected DV. The total increment of fruit volume during 4 weeks was 6,226.8 cm³·fruit^-1 in SENW, which was about 1.5 times higher than that of 4,755.3 cm³·fruit^-1 in EW. This result was greatly affected by daily integrated solar radiation. Therefore, direction of single-span greenhouse in summer cultivation affects amount and intensity of solar radiation and fruit enlargement, and the direction of south-north is more suitable than that of east-west.