( Stems ( ( In ( vascular plants ) ) ( , ( ( stems ( ( are ( the organs ) ) ( that ( ( hold plants ) ( upright ( so ( they ( can ( get ( ( the ( ( sunlight and ) air ) ) ( they need ) ) ) ) ) ) ) ) ) ) ) . ) ) ) )
(ROOT (S (ADVP (RB Stems)) (PP (IN In) (NP (NN vascular) (NNS plants))) (, ,) (VP (VBZ stems) (SBAR (S (VP (VBP are) (NP (DT the) (NNS organs)) (SBAR (IN that) (S (NP (VB hold) (NNS plants)) (VP (VBP upright) (SBAR (IN so) (S (NP (PRP they)) (VP (MD can) (VP (VB get) (NP (NP (DT the) (NN sunlight) (CC and) (NN air)) (SBAR (S (NP (PRP they)) (VP (VBP need)))))))))))))))) (. .)))
Stems   In vascular plants, stems are the organs that hold plants upright so they can get the sunlight and air  they need.
(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))))))))))))))) (. .)))