Photosynthetic Characteristics of Cassava (Manihot esculenta Crantz), a C_3 Species with Chlorenchymatous Bundle Sheath Cells

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Cultivars of cassava, Manihot esculenta Crantz, were studied to determine the mechanism of photosynthetic carbon assimilation in this species. The results, contrary to recent reports, indicate that cassava is a C_3 plant based on a number of physiological and biochemical photosynthetic characteristics. The CO_2 compensation points among 10 cassava cultivars ranged from 55 to 62 μl・liter^<-1>, which was typical for C_3 plants including castor bean, a member of the same family (Euphorbiaceae). The initial products of photosynthesis in cassava are C_3-like; the activities of several key C_4 enzymes in cassava are low and similar to those of C_3 plants. Data on the rates of photosynthesis per unit of leaf area and the photosynthetic response of cassava to CO_2 is also consistent with C_3 photosynthesis. Cassava has a distinctive chlorenchymatous vascular bundle sheath located below a single layer of palisade cells. Unlike C_3-C_4 intermediates and C_4 species, the bundle sheaths of cassava are not surrounded by mesophyll cells. The bundle sheath cells which occur at high frequency in cassava may function in both photosynthesis and transport of photosynthates in the leaf.
日本植物生理学会の論文