The dark respiration of five tropical rain forest and five coastal desert plant species experienced in very high CO 2 concentrations(>1500μmol/mol)in Biosphere 2 for more than 4.5 years,was studied using a portable LI 6400 Photosynthesis system.The result showed that the average dark respiration of the rain forest species was (0 56±0 19)μmol CO 2/m 2·s under near ambient CO 2 concentration (350～400μmol/mol),and that of the desert species was(0 98±0 72)μmol CO 2/m 2·s.The dark respiration of both ...