( A ( ( is ( ( the ( large ( central vacuole ) ) ) ( which ( contributes ( to ( cell expansion ) ) ) ) ) ) . ) )
(ROOT (S (NP (NNP A)) (VP (VBZ is) (NP (NP (DT the) (JJ large) (JJ central) (NN vacuole)) (SBAR (WHNP (WDT which)) (S (VP (VBZ contributes) (PP (TO to) (NP (NN cell) (NN expansion)))))))) (. .)))
A is the large central vacuole which contributes to cell         expansion.
(ROOT (S (NP (DT The) (NN cell) (NN sap)) (VP (VBZ is) (NP (NP (DT the) (NN liquid)) (PP (IN inside) (NP (DT the) (JJ central) (NN vacuole))))) (. .)))