( ( Healthy plants ) ( ( ( give off ) ( oxygen ( during photosynthesis ) ) ) . ) )
(ROOT (S (NP (JJ Healthy) (NNS plants)) (VP (VBP give) (PRT (RP off)) (NP (NP (NN oxygen)) (PP (IN during) (NP (NN photosynthesis))))) (. .)))
Healthy plants give off oxygen during photosynthesis.
(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))))) (. .)))