( Fungi ( ( are ( ( ( the ( ( most important ) decomposers ) ) ( of ( structural ( plant compounds ) ) ) ) ( -LRB- ( ( ( ( cellulose and ) lignin ) ( but ( note ( that ( lignin ( ( is not ) ( ( broken down ) ( when ( oxygen ( is absent ) ) ) ) ) ) ) ) ) ) -RRB- ) ) ) ) . ) )
(ROOT (S (NP (NNP Fungi)) (VP (VBP are) (NP (NP (DT the) (ADJP (RBS most) (JJ important)) (NNS decomposers)) (PP (IN of) (NP (JJ structural) (NN plant) (NNS compounds))) (PRN (-LRB- -LRB-) (NP (NP (NN cellulose) (CC and) (NN lignin)) (SBAR (CC but) (S (VP (VBP note) (SBAR (IN that) (S (NP (NN lignin)) (VP (VBZ is) (RB not) (VP (VBN broken) (PRT (RP down)) (SBAR (WHADVP (WRB when)) (S (NP (NN oxygen)) (VP (VBZ is) (ADJP (JJ absent))))))))))))) (-RRB- -RRB-)))) (. .)))
Fungi are the most important decomposers of structural plant compounds (cellulose and lignin but note that lignin is not broken down when oxygen is absent).
(ROOT (S (NP (NNP Cellulose)) (VP (VP (VBZ is) (NP (NP (CD one)) (PP (IN of) (NP (NP (DT the) (ADJP (RBS most) (JJ common)) (JJ biochemical) (NNS compounds)) (PP (IN on) (NP (NN earth))))))) (CC and) (VP (VBZ is) (VP (VBN found) (PP (IN in) (NP (DT all) (NNS plants)))))) (. .)))