( ( This structure ) ( ( is ( ( ( ( ( ( the rhizome ) , ) or ) ( underground stem ) ) , ) ( that ( ( allows ( the plant ) ) ( to overwinter ) ) ) ) ) . ) )
(ROOT (S (NP (DT This) (NN structure)) (VP (VBZ is) (NP (NP (NP (DT the) (NN rhizome)) (, ,) (CC or) (NP (JJ underground) (NN stem)) (, ,)) (SBAR (WHNP (WDT that)) (S (VP (VBZ allows) (NP (DT the) (NN plant)) (PP (TO to) (NP (NN overwinter)))))))) (. .)))
This structure is the rhizome, or underground stem, that allows the plant to overwinter.
(ROOT (S (NP (DT The) (NN stem)) (VP (VBZ is) (NP (NP (DT the) (JJ basic) (NN structure)) (SBAR (WHNP (WDT that)) (S (VP (VBZ holds) (S (NP (NNS plants)) (ADJP (JJ upright))) (, ,) (S (VP (VBG allowing) (NP (NNS plants)) (S (VP (TO to) (VP (VB get) (NP (NP (DT the) (NN sunlight) (CC and) (NN air)) (SBAR (S (NP (PRP they)) (VP (VBP need))))))))))))))) (. .)))