Kiwifruit Cell Walls: towards an Understanding of Softening?*

Kiwifruit is an excellent model in which to study events in the cell wall that lead to fruit becoming soft. In kiwifruit, softening can be separated into distinct phases, with the phase associated with the most extensive and rapid loss of firmness being well-separated temporally from that associated with the respiratory climacteric and ethylene production. This contrasts with tomato, avocado, and many other fruit where softening changes, ethylene production, and the climacteric occur concurrently. The changes that occur in the kiwifruit cell wall during the softening process have been extensively characterised by chemical analyses, by histochemical and immunolocalisation techniques, and by monitoring the activity and expression of wall-associated enzymes.