INFLUENCE OF IRRADIANCE ON PHOTOSYNTHESIS, MORPHOLOGY AND GROWTH OF MANGOSTEEN (GARCINIA-MANGOSTANA L) SEEDLINGS

The influence of shading intensity on growth, morphology and leaf gas exchange of mangosteen (Garcinia mangostana L.) seedlings was investig ated over a 2-year period. Diurnal gas exchange studies revealed signi ficantly higher carbon gain for leaves grown in 20 or 50% shade compar ed to leaves grown in 80% shade. Seedlings grown in 20 or 50% shade ac cumulated significantly more dry weight than seedlings grown in 80% sh ade during the 2-year study period. Seedlings grown in decreased shade showed decreased leaf size, increased leaf thickness, lower specific leaf area (SLA) and higher stomatal frequency. Less shaded seedlings a lso allocated relatively more dry matter to roots than shaded seedling s and exhibited a significant reduction in leaf area relative to total plant dry weight (leaf area ratio). Increased leaf number, enhanced b ranching and shorter internodes resulted in a more compact appearance of less shaded seedlings. Irrespective of light conditions, mangosteen seedlings exhibited inherently slow growth because of low photosynthe tic rates per unit leaf area, low SLA, low leaf area ratios and ineffi cient root systems.