( ( The ( open-headed arrows ) ) ( ( indicate ( the ( is-instance-of relationship ) ) ) . ) )
(ROOT (S (NP (DT The) (JJ open-headed) (NNS arrows)) (VP (VBP indicate) (NP (DT the) (JJ is-instance-of) (NN relationship))) (. .)))
The open-headed arrows indicate the is-instance-of relationship.
(ROOT (S (NP (JJ Reversible) (NNS reactions)) (VP (VBP are) (VP (VBN indicated) (PP (IN by) (NP (NP (JJ opposite-headed) (NNS kinds)) (PP (IN of) (NP (NNS arrows))))))) (. .)))
Reversible reactions are indicated by opposite-headed kinds of arrows.