Vol. 69 No: 5

Title:
Growth and Photosynthesis of Oncidium ‘Goldiana’

Authors:
C.S. HEW and J.W.H. YONG

pp: 809-820

Abstract:
The growth and photosynthesis of Oncidium ‘Goldiana’, a popular tropical orchid for cut flower production, were studied. Four main developmental stages were identified: bud stage, plantlet stage, unsheathing stage and pseudobulb stage. Pseudobulb formation occurred during the unsheathing stage which was closely followed by the formation of an inflorescence. The pseudobulb is of the heteroblastic type (arising from a single node) and lacks stomata. It is a C₃ shade plant based on chlorophyll a/b ratio, CO₂ compensation point, post-illumination CO₂ outburst and light response curves. The formation of new sinks such as inflorescence and axillary bud have a significant effect on the rate of photosynthesis of certain leaves. The photosynthetic rates of leaves L2 and L3 increased during the development of the axillary bud and inflorescence respectively. Pseudobulbs have high water content and contain chlorophyll but show no sign of gas exchange in light and dark. However, fixation of CO₂ is possible in light with partial removal of the underlying cuticle.

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