Influence of Photosynthetic Capacity, Irradiance and SO₂ Fumigation on Shoot Growth of Azalea (Rhododendron) Cultivars

Abstract

Azalea (Rhododendron) shoot growth is of considerable concern to commercial growers, because it requires considerable cultural time. Ceulemans et al. (2) found a positive relationship between photosynthesis and shoot growth of closely related greenhouse cultivars. The studies reported here have utilized a method of determining oxygen evolution of leaf segments in carbon dioxide saturation developed by Steffen & Palta (6), to investigate a possible relationship between photosynthesis and shoot growth of distantly related outdoor azalea cultivars. Badger (1) considered such determination to be net oxygen flux. The effect of SO₂ on post-fumigation photosynthesis and shoot growth of 2 cultivars has been investigated. Lorenc-Plucinska (3) found that Scots pine seedlings with a high photosynthetic rate were more susceptible to SO₂. Because Pettersen (5) reported on the stimulating effect of long days on azalea shoot growth at high temperatures, the effect of photoperiod on net oxygen flux was investigated. Also the effect of leaf position and PPFD on net oxygen flux of leaf segements were determined.