( ( In ( higher plants ) ) ( , ( ( oxygen gas ) ( ( is required ) . ) ) ) )
(ROOT (S (PP (IN In) (NP (JJR higher) (NNS plants))) (, ,) (NP (NN oxygen) (NN gas)) (VP (VBZ is) (VP (VBN required))) (. .)))
In higher plants, oxygen gas is required.
(ROOT (S (NP (NN Oxygen) (NN gas)) (VP (VBZ is) (VP (VBN given) (PRT (RP off)) (PP (IN by) (NP (NNS plants))))) (. .)))