The Effect of Temperature and Quantum Flux Density on the Morphology, Physiology, and Flowering of Hybrid Geraniums1

Abstract

Hybrid geraniums ( Pelargonium × hortorum Bailey) cv. Sooner Red were grown at temperatures ranging from 10–32°C and at various quantum flux densities. The time to visible bud stage (<0.5 cm diameter) was negatively correlated to quantum flux density at a given temperature. The time required from visible bud to flower stage was negatively correlated with temperature while light had no effect. Leaf thickness, number of palisade layers, and specific leaf weight were negatively correlated with temperature, and specific leaf weight was positively correlated with quantum flux density at a given temperature. Net photosynthetic rate ranged from 5–38 mg CO 2 dm -2 hr -1 for temperatures of 10-37° and was optimum at 20-32°. The Q 10 of respiration for hybrid geranium leaves was about 2.2.