Effect of CO2 Enrichment on the Photosynthesis and Dry Matter Accumulation in the Oriental Hybrid Lily 'Siberia'

We investigated the effects of CO2 enrichment on photosynthesis, growth, and dry matter accumulation in the Oriental hybrid lily 'Siberia'. The photosynthetic rate increased as the CO2 concentration was elevated compared to the ambient level. The increase in the photosynthetic rate was greater in the low concentration range and lower in the high concentration range. The relationship between the light intensity-photosynthetic rate and temperature-photosynthetic rate was investigated under different CO2 concentrations. The entire light-photosynthesis and temperature-photosynthesis curves moved toward a considerably higher photosynthetic rate when the CO2 concentration was increased from 380 ppm to 1000 ppm. In contrast, when the CO2 concentration was increased from 1000 ppm to 2000 ppm, the increase in the entire light-photosynthesis curve was small. The relationship between the CO2 concentration and the maximum temperature point of the photosynthetic rate was unclear. We also cultured 'Siberia' lily plants with and/or without CO2 enrichment (1500 ppm) altered before (the early stage) and after (the late stage) the visible flower bud stage. The CO2 enrichment increased dry weights dry weight/fresh weight ratios of whole plants, and individual parts at flowering, resulting in improved cut flower quality and enlargement of the mother bulb and daughter bulblets. The effective period of CO2 enrichment was after the visible flower bud stage. In cases where CO2 enrichment was effective for dry matter accumulation, the dry matter distribution ratios of the mother bulb and daughter bulblets to the whole plant were high, and those of the leaves, stem, and flower buds were low. The relative growth rate and net assimilation rate from planting to the flowering stage were increased with CO2 enrichment applied after the visible flower bud stage, indicating that the dry matter accumulation and photosynthesis were enhanced. Finally, the issues that need to be addressed for applying practical CO2 enrichment technology to various lilies are discussed.