( Trees ( ( ( produce ( oxygen ( as ( a byproduct ) ) ) ) ( through ( the ( photosynthesis process ) ) ) ) . ) )
(ROOT (S (NP (NNP Trees)) (VP (VBP produce) (NP (NP (NN oxygen)) (PP (IN as) (NP (DT a) (NN byproduct)))) (PP (IN through) (NP (DT the) (NN photosynthesis) (NN process)))) (. .)))
Trees produce oxygen as a byproduct through the photosynthesis process.
(ROOT (S (NP (NNP Oxygen)) (VP (VBZ is) (VP (VBN made) (PP (IN by) (NP (NP (NNS trees)) (CC and) (NP (JJ other) (NNS plants)))) (PP (IN during) (NP (NN photosynthesis))))) (. .)))