VARIATION IN PHOTOSYNTHETIC CHARACTERISTICS ALONG THE LEAF BLADE OF ONCIDIUM GOLDIANA, A C-3 TROPICAL EPIPHYTIC ORCHID HYBRID

Photosynthesis was studied in relation to leaf development in leaves o f the tropical C-3 epiphytic orchid hybrid Oncidium Goldiana. Variatio ns in total chlorophyll, maximum Rubisco activity, and maximum photosy nthetic capacity were detected along the leaf blade in both developing and fully expanded mature leaves. Increasing gradients of total chlor ophyll, Rubisco, and photosynthetic activity were detected from the ba se to the apex in both developing and fully expanded mature leaves. Li ght response curves of basal and apical portions of leaves showed a hi gher photosynthetic capacity in the apex regardless of the stage of de velopment. Correlation analyses revealed significant positive relation ships between total chlorophyll, maximum Rubisco activity, and maximum photosynthetic capacity. Our results indicate a gradient of photosynt hetic capacity along developing and fully expanded mature leaf blades of Oncidium Goldiana.