Relationship Between Evolutionary Adaptation and Gas Exchange Characteristics of Diverse Sorghum Taxa

Abstract

Ten species and varieties of Sorghum were conditioned to either full or part sunlight. Gas exchange parameters of attached leaves were determined under a range of levels of photosynthetically active radiation and leaf temperature. S. arundinaceum which originated in the low light environment of equatorial forests was capable of higher rates of photosynthesis and greater stomatal opening if it was conditioned to low rather than high radiation conditions. In this respect it differed from the other species though all have the characteristics of plants with the C4 pathway of photosynthesis. Generally species from high radiation environ. ments were capable of the highest rates of photosynthesis though some exceptions were noted. Genetic implications are briefly discussed.