Effect of temperature and irradiance on vegetative and generative development in Pelargonium × hortorum ‘Radio’

Abstract

Vegetatively propagated plants of Pelargonium × hortorum ‘Radio’ were grown at 8 combinations of irradiance and temperature levels; 4 or 22 W m −2 combined with 12, 15, 18 or 21°C. Increase in leaf number, leaf area, shoot and number of inflorescences per plant were all greater at 22 W m −2 than at 4 W m −2. At 22 W m −2, increase in temperature affected leaf number, leaf area and shoot number, but not inflorescence number. However, at 4 W m −2, number of inflorescences — but not leaf or shoot number — was affected by temperature. When effects of temperature differences were observed, the highest temperature resulted in the greatest number of leaves and shoots and the largest leaf area, but the lowest number of inflorescences per plant. The results indicate that photosynthesis or energy metabolism is of importance to floral initiation in Pelargonium × hortorum.