Effects of the Number of Air Changes per Hour of the Closed Vessel and the Photosynthetic Photon Flux on the Carbon Dioxide Concentration Inside the Vessel and the Growth of Strawberry Plantlets in vitro

Abstract

Effects of the number of air changes per hour of the closed vessel (1.5 and 2.7 h^-1) and the photosynthetic photon flux (PPF, 34.3 and 133 μmol m^-2s^-1) on the CO₂concentration inside the vessel (C_in) and the growth of strawberry plantlets in vitro were investigated.
Cin during the photoperiod was lower than CO₂outside the vessel (Cout, inside the culture room) on 5 days after the start of experiments in all treatments. On 20 days after the start of experiments, C_inwas lower than C_out (350-400 ppm) by 100-300 ppm. The difference in CO₂concentration between inside and outside was relatively larger in the higher PPF treatment and in the larger number of air changes per hour treatment.
On 20 days after the start of experiments, the dry weight of the plantlet was larger in the higher PPF treatment than in the lower PPF treatment. However, the difference in the dry weight was not so large among the treatments, comparing with the large differences in C_inamong the treatments.
Relative growth rate, chlorophyll content, net photosynthetic rate, dark respiration rate etc. were estimated to explain the relatively small difference in the dry weight among the treatments. Furthermore, suggestions were made to improve the environment in the vessel further for promoting the plantlet growth.