( ( When ( ( the colony ) starves ) ) ( , ( cells ( ( aggregate ( to ( form moulds ) ) ) . ) ) ) )
(ROOT (S (SBAR (WHADVP (WRB When)) (S (NP (DT the) (NN colony)) (VP (VBZ starves)))) (, ,) (NP (NNS cells)) (VP (VBZ aggregate) (S (VP (TO to) (VP (VB form) (NP (NNS moulds)))))) (. .)))
When the colony starves, cells aggregate to form moulds.
(ROOT (S (SBAR (WHADVP (WRB When)) (S (NP (NN food)) (VP (VBZ is) (ADJP (JJ scarce))))) (, ,) (NP (VBG starving) (NNS cells)) (VP (VBP secrete) (NP (NP (DT a) (NN molecule)) (SBAR (WHNP (WDT that)) (S (VP (VBZ stimulates) (NP (VBG neighboring) (NNS cells)) (PP (TO to) (NP (NN aggregate)))))))) (. .)))