Photosynthetic capacity of peanut genotypes under natural and controlled environment

Photosynthetic capacity of runner peanuts (Arachis hypogaea L.) cv. IAC-Caiapo and cv. Runner IAC-886 was evaluated under controlled condition, in plants grown on pots maintained in a greenhouse, and in irrigated plants grown on soil-filled tanks made of concrete, and exposed to natural ambient condition. CO2 net assimilation rate (A) response in relation to photosynthetic photon flux density (DFFF) was better in controlled condition, but in both conditions the same maximum A of ca. 28 mu mol m(-2) s(-1) was reached. Under controlled condition, light saturation was about 1,000 mu mol m(-2) s(-1), although under natural condition, saturation occurred at higher DFFF. Leaf temperature between 23 and 36 degrees C did not affect A, and leaf to air vapor pressure difference caused partial stomatal closing, decreasing A, when above 3.0 kPa. Photosynthetic capacities of the two cultivars were similar. Both cultivars showed good adaptation to daily changes of environmental conditions that occur during summer, showing dynamic photoinhibition of photosynthesis in the beginning of the afternoon (13-14h), as revealed by a reversible decrease in the maximum quantum efficiency (Fv/Fm) of photosystem II.