( ( ( ( ( ( Green plants ) ( ( conduct photosynthesis ) ( to ( make ( their food ) ) ) ) ) , ) and ) ( oxygen ( is ( ( a by-product ) ( of ( this process ) ) ) ) ) ) . )
(ROOT (S (S (NP (NNP Green) (NNS plants)) (VP (VBP conduct) (NP (NN photosynthesis)) (S (VP (TO to) (VP (VB make) (NP (PRP$ their) (NN food))))))) (, ,) (CC and) (S (NP (NN oxygen)) (VP (VBZ is) (NP (NP (DT a) (NN by-product)) (PP (IN of) (NP (DT this) (NN process)))))) (. .)))
Green plants conduct photosynthesis to make their food, and oxygen is a by-product of this 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))))) (. .)))