Acyl-ACP thioesterase involved in the production of fatty acids and beta-keto fatty acids. Can produce fatty acids of long chain (14:1 and 16:1) and beta-keto fatty acids of medium to long chain (8:0, 10:0, 12:0, 12:1, 14:0 and 16:0) when expressed in a heterologous organism (E.coli). Possesses thioesterase activity for lauroyl-ACP (12:0-ACP) in vitro. May play a role in the generation of long fatty acids in the chloroplast. Highly expressed in stems and flowers and at lower levels in rosette leaves, cauline leaves and siliques. Belongs to the 4-hydroxybenzoyl-CoA thioesterase family. Truncated N-terminus.