( ( ( Gas exchange ) ( in plants ) ) ( ( is ( dominated ( by ( ( the roles ) ( of ( ( ( carbon dioxide ) and ) ( water vapor ) ) ) ) ) ) ) . ) )
(ROOT (S (NP (NP (NNP Gas) (NN exchange)) (PP (IN in) (NP (NNS plants)))) (VP (VBZ is) (VP (VBN dominated) (PP (IN by) (NP (NP (DT the) (NNS roles)) (PP (IN of) (NP (NP (NN carbon) (NN dioxide)) (CC and) (NP (NN water) (NN vapor)))))))) (. .)))
Gas exchange in plants is dominated by the roles of carbon dioxide and water vapor.
(ROOT (S (NP (NP (DT The) (NN combustion)) (PP (IN of) (NP (NN propane) (NN gas)))) (VP (VBZ produces) (NP (NP (NN carbon) (NN dioxide)) (CC and) (NP (NN water) (NN vapor)))) (. .)))