シンビジウムの花蕾における呼吸変化と「花飛び」現象との関連について

Abstract

Respiratory changes leading to flower bud blasting in the orchid Cymbidium × Sazanami 'Haru-no-umi' at high temperature were examined. When plants bearing inflorescences grown between 5° to 20°C (low) were transferred to a phytotron kept at 30° day/25°C night (high), CO2 evolution by the flower buds decreased rapidly and reached about 1/3 of the initial rates during two weeks with rise of temperature coefficient (Q10) near to 3. Flower stalks and bracts showed similar but slower reductions in CO2 evolution. Their Q10 values were around 2 and not different from those of the control inflorescences placed at low temperatures (20°/15°C). Both respiratory rates and Q10 values remained relatively constant in the control inflorescences. Respiratory rates of flower buds grown at natural low temperatures were high on fresh weight basis and increased with flower bud development on flower bud basis. The respiratory quotient (RQ) was between 1.15 and 1.35. On the contrary, the rates of those grown under natural high temperatures (25°C ?? ) showed lower values and did not increase on flower bud basis. The RQ decreased dramatically from 1.5 to 0.7. Application of gibberellic acid (GA3), which prohibited flower buds from blasting, suppressed the reductions of respiratory rates and RQ values. The results indicate that reduction of respiratory rates, RQ decrease and Q10 rise, are involved in the blasting of Cymbidium flower buds caused by high temperature.