( ( The oxygen ) ( ( ( originates ( as ( ( a byproduct ) ( of photosynthesis ) ) ) ) ( by plants ) ) . ) )
(ROOT (S (NP (DT The) (NN oxygen)) (VP (VBZ originates) (PP (IN as) (NP (NP (DT a) (NN byproduct)) (PP (IN of) (NP (NN photosynthesis))))) (PP (IN by) (NP (NNS plants)))) (. .)))
The oxygen originates as a byproduct of photosynthesis by plants.
(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))))) (. .)))