Does cholinesterase participate in the intercellular interactions in pollen-pistil system?

Hydrolysis of acetylthiocholine and butyrylthiocholine has been observed in aqueous extracts from petunia pollen and pistils. The reproductive organs of self-compatible clone showed a higher rate of choline ester hydrolysis than those of self-incompatible clone. The highest rate of acetylthiocholine hydrolysis blocked by the cholinesterase inhibitors (physostigmine and neostigmine) was characteristic for the pollen of self-compatible clone. The incomplete (25-40%) inhibition of hydrolysis in pistil extracts of self-compatible clone suggests the presence of unspecific esterases. The eight-fold lower hydrolysis was observed in the pistils of self-incompatible clone as compared to the pistils of compatible clone; neostigmine completely blocked this low hydrolytic activity. The treatment of flower buds with physostigmine and neostigmine (10(-5) - 10(-3) M) decreased the seed production by 10-20% in compatible clone. When the surfaces of pistil stigmae were treated with physostigmine and neostigmine (10(-5) - 10(-3) M) before pollination, the seed formation was inhibited by 95% after both self- and cross-pollination.