Effects of CO₂ Enrichment on Harvest Time and Cut Flower Quality in Winter Cultivation of Eustoma grandiflorum in Kochi Prefecture

Abstract

Winter cultivation of Eustoma grandiflorum is commonly associated with flower bud blasting, leading to a reduced cut flower quality. CO₂ enrichment is expected to alleviate this problem. In this study, we investigated the effects of CO₂ enrichment on cut flower quality of E. grandiflorum, cultivated during winter in a greenhouse located in Kochi Prefecture, where the controlled daytime temperature was 25°C. Plants were cultivated under three greenhouse conditions: (i) without CO₂ enrichment and under a controlled daytime temperature of 25°C (non-enriched/25°C), (ii) with CO₂ enrichment and under a controlled daytime temperature of 25°C (enriched/25°C), and (iii) with CO₂ enrichment and under a controlled daytime temperature of 30°C (enriched/30°C). The harvest dates of enriched/30°C were earlier than those of non-enriched/25°C. The two treatments with CO₂ enrichment caused increases in the cut flower length and number of flowers. We clarified that the improvement of cut flower quality in enriched/25°C was approximately equivalent to that in enriched/30°C, although the CO₂ concentration during the daytime was maintained at 1,000 ppm for a shorter time in enriched/25°C than in enriched/30°C as the ventilation windows of the greenhouse were kept open for a longer time in the former treatment.