( ( Without carotenoids ) ( ( photosynthesis ( in ( an ( oxygenic atmosphere ) ) ) ) ( ( would ( be impossible ) ) . ) ) )
(ROOT (S (PP (IN Without) (NP (NNS carotenoids))) (NP (NP (NN photosynthesis)) (PP (IN in) (NP (DT an) (JJ oxygenic) (NN atmosphere)))) (VP (MD would) (VP (VB be) (ADJP (JJ impossible)))) (. .)))
Without carotenoids photosynthesis in an oxygenic atmosphere would be impossible.
(ROOT (S (NP (NP (DT The) (NN process)) (ADJP (JJ responsible) (PP (IN for) (NP (NP (DT the) (NN presence)) (PP (IN of) (NP (NP (NN oxygen)) (PP (IN in) (NP (PRP$ our) (NN atmosphere))))))))) (VP (VBZ is) (NP (NN photosynthesis))) (. .)))