Relation in Grasses of High Photosynthetic Capacity and Tolerance to Atrazine1

Abstract

Zea mays L., Saccharum officinarum L., the sorghums, and several other grass species have maximum rates of photosynthesis near 60 mg CO2 dm‐2 hr‐1 and are tolerant of the herbicide, 2‐chloro‐4‐ethylamino‐6‐isopropylaminos‐s‐triazine (atrazine). In contrast, the small grains and numerous other grasses have maximum rates of photosynthesis of about 20 mg CO2 dm‐2 hr‐1 and are susceptible to atrazine. The correlation between these traits suggested that atrazine tolerance might be a useful selection criterion to detect efficient photosynthesis. Using this hypothesis, Digitaria and Setaria species which are tolerant of atrazine, were found to have efficient photosynthesis.