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

The aim of this study was to determine the effect of relative humidity and air supply on the physiological and stomatal responses in peloric Phalaenopsis ‘Breeding No.522’ during acclimatization. Experiments were carried out in four different conditions: 1) relative humidity (RH) 85% without air supply (RH85% Non-air), 2) RH 85% with air supply (RH85% Air), 3) RH 75% without air supply (RH75% Non-air), and 4) RH 75% with air supply (RH75% Air). Plantlets were transferred into a custom-designed container for acclimatization, into which 10cc/min air was supplied continuously during the 10-day experimental period. The lowest tip burn (20%) was observed in plantlets treated with RH 85% Non-air, whereas the highest tip burn (55%) was found in plantlets with RH75% Air treatment. The photosynthetic rate did not exhibit a significant difference among treatments. However, stomatal conductance and transpiration rate were higher in the RH75% Non-air plantlets than in the other three treatments. In CAM plants, malic acid accumulation correlates with photosynthesis activity, which can be inferred by measuring the leaf pH at night. The overall pH of the leaves in all treatments was low and the lowest value of pH was 4.8 in the RH75% Non-air plantlets. Stomatal density was significantly higher in conditions with high humidity (85%) or with air supply, suggesting that high humidity and air supply have synergistic effects for increasing stomatal density during the Phalaenopsis acclimatization. On the other hand, low humidity (75%) and air supply enlarged stomatal pore size.