Photosynthesis in Grass Species Differing in Carbon Dioxide Fixation Pathways: II. A Search for Species with Intermediate Gas Exchange and Anatomical Characteristics

摘要: Thirty-three grass species were examined in two experiments an attempt to locate plants with photosynthetic responses O2, CO2 compensation concentrations, and leaf anatomy intermediate those of C3 C4 species. Species included seven from the Laxa group Panicum genus, one which, P. milioides Nees ex Trin., has been reported earlier have characteristics. The O2-sensitive photosynthesis typical showed more than 37% increase apparent at 2% O2 compared 21% 25 C 335 microliters per liter CO2, whereas milioides, schenckii Hack., decipiens members Panicum, increases ranged 30%. remainder did not respond O2. characteristic exhibited concentrations 44 or higher 27.5 characterized as O2-insensitive had values less. concentration (Г) schenckii, 10.3 23.3 liter. Other response Г either (P. laxum Sw., hylaeicum Mez., rivulare Trin.) prionitis Griseb.) plants. Leaves poorly developed nearly empty bundle sheath cells, much larger distances mesophyll cell numbers between veins ones. Vein spacings 0.18 0.28 millimeter number 5.2 7.8. While these vein are closer most grasses, Dactylis similar Panicums Glyceria striata, another plant, separated by only four cells 0.12 millimeter. Bundle three contained greater quantities organelles for grasses.