Variation in photosynthetic characteristics along the leaf blade of Oncidium Goldiana, a C3 tropical epiphytic orchid hybrid

Abstract

Photosynthesis was studied in relation to leaf development in leaves of the tropical C3 epiphytic orchid hybrid Oncidium Goldiana. Variations in total chlorophyll, maximum Rubisco activity, and maximum photosynthetic capacity were detected along the leaf blade in both developing and fully expanded mature leaves. Increasing gradients of total chlorophyll, Rubisco, and photosynthetic activity were detected from the base to the apex in both developing and fully expanded mature leaves. Light response curves of basal and apical portions of leaves showed a higher photosynthetic capacity in the apex regardless of the stage of development. Correlation analyses revealed significant positive relationships between total chlorophyll, maximum Rubisco activity, and maximum photosynthetic capacity. Our results indicate a gradient of photosynthetic capacity along developing and fully expanded mature leaf blades of Oncidium Goldiana.