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Ecophysiological observations within the Phaseolus coccineus complex

Abstract:

The complex Phaspolus coccineus as defined by Delgado (1985) has a number of subspecies and varieties cultivated in cool-temperate regions in Mexico. Most of these cultivars represent indigenous materials locally adapted, through domestication processes in situ, to the prevalent environmental and cultural practices. Ph. coccineus is grown as monoculture or as mixed-crop. One of the subspecies,£ h.. coccineus sbsp. darwinianus (PCD) is normally grown in association with maize throughout many high-moist places south of Mexico and in Central America. Many aspects of bean-maize mixed crops have been reviewed (Francis 1986), although most of them are applicable to the maize-£ Ji. vulgaris association. Because of their difference in nitrogen metabolism, gas exchange and photosynthetic pathway, mixed legume (C3)-grass (C4) crops are thought to be either a symbiotic (Lepiz 1974) or competitive type of interactions (Francis 1986). Because most studies have been focused on yield and yield components of mixtures (Kohashi 1990), very little have been studied on the resource use and efficiency of nitrogen, light and water. Only very few studies have addressed directly the physiological consequences of the association in terms of gas-exchange (Lepiz 1974) or water.