Correlated alterations in leaf and flower morphology and rate of leaf photosynthesis in a midribless (mbl) mutant of Panicum maximum Jacq.

A midribless (mbl) mutant of Panicum maximum Jacq. induced by ethylmethanesulfonate treatment was characterized with respect to morphological and physiological features. The absence of the midrib was accompanied by a reduction of the large veins in the leaf lamina from 25% of total veins found in the wildtype to 13%. The florets of the mutant had no carpel but one or two extra stamens were observed. Similar phenotypic changes have been described for an ovaryless (ovl) mutant of barley. This supports the suggestion that a common morphogenetic determinant in wildtype plants induces both the development of the main midrib in leaves and the carpel in florets. Photosynthetic rate, CO2-compensation point and export of photosynthates, however, were similar in leaves of mutant and wild type plants.