Effect of fogging on survival rate and photophysiological response during the initial growth period of strawberries in a greenhouse

In Korea, the relative humidity (RH) on a daytime in a greenhouse is very low during the initial growing phase of the strawberry plants, i.e., from October to November. The aim of this study was to investigate the survival rate and photophysiological response of two strawberry cultivars to fogging treatment under low RH condition in the greenhouse. The greenhouse to which the fog spray was applied showed a lower temperature of 2-5°C and a relative humidity of 5-25% higher than that of the control. The photosynthetic rate and stomatal conductance of strawberry leaves were not significantly affected by fogging treatment, but the leaf transpiration rate was significantly affected by fog spray. In both cultivars applied with fog spray, the older leaves had a high transpiration rate, but a relatively low photosynthetic rate. In ‘Seolhyang’ applied with fog spray, the values related to the energy fluxes per reaction center in the chlorophyll a fluorescence of leaves such as ABS/RC, TR₀/RC, ET₀/RC and DI₀/RC, were significantly higher than the control; while, such effects of fogging were not seen for ‘Kuemsil’. ‘Seolhyang’ showed a significantly higher survival rate upon fogging treatment (98.1%) than the control (61%), while in ‘Kuemsil’ fogging treatment did not affect the survival rate. In conclusion, although there was a difference in the effect of fog spray between the two cultivar, greenhouse grown strawberry plants are sensitive to low RH and fogging treatment is used improving the growth and physiology of the plants at initial phase after planting.