Photosynthetic Carbon Assimilation in a Shootless Orchid, Chiloschista usneoides (DON) LDL

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Abstract
Photosynthetic carbon assimilation in the roots of a shootless orchid Chiloschista usneoides (DON) LDL involves the synthesis and accumulation of malic acid from CO2 in darkness. Malic acid is consumed in the light. The roots do not possess stomata or any means of diurnally regulating the diffusive conductance of the pathway between the internal gas phase of the plant and the atmosphere. Regulation of internal CO2 concentration near to atmospheric levels avoids a large net loss of CO2 to the atmosphere during malic acid consumption in the light. The water-absorbing function of the velamen conflicts with the photosynthetic function of the roots. Plants with water-saturated velamina do not acquire CO2 from the atmosphere at night.