Effects of CO₂ Enrichment on Growth, Photosynthesis and Physiological Activity of Roots of Dendranthema × grandiflorum (Ramat.) Kitamura

Abstract

To assess the effect of CO₂ enrichment on growth of greenhouse chrysanthemum, the plants were cultivated in the phytotron with 300, 600 and 1, 200 ppm CO₂.
1. CO₂ enriched plants showed a significant increase in stem length, number of leaves, leaf area, and fresh and dry weights. The greatest rate of increase after 60 days of CO₂ enrichment was observed in the dry weight of roots (39%). Flower bud formation was delayed 3 days under CO₂ enriched condition.
2. No difference in photosynthetic rates of whole plants measured in 400 and 800 ppm CO₂ was observed among those grown under high CO₂ (600 or 1, 200 ppm) and those grown in ambient air (300 ppm). After 60 days of exposure to ambient and high CO₂, the photosynthetic rate measured in 800 ppm CO₂ declined markedly compared to the rate at the beginning of the treatment.
3. TTC (2, 3, 5-triphenyl tetrazolium chloride) reductive activity of roots decreased under CO₂ enriched atmosphere, but it increased on a per plant basis because fresh weight of the roots increased. There was a high positive correlation between TTC reduction per plant and the fresh weight of the top (aerial part).