ANATOMICAL STUDIES ON MISSHAPEN PISTACHIO NUTS
The process leading to tissue degeneration in pistachio fruit pericarp may start as early as the 2nd week after bloom, although in some cases its onset may occur later. The most affected tissue is the endocarp parenchyma, whose cells necrotize and collapse, thus causing shrinkages and fractures. In the worst cases only the mesocarp (hull) remains functional, constituting a thin protection for the embryo, while no shell is present in the affected areas. The degeneration may also involve the mesocarp, at times with hypertrophies. The localised curly aspect of the nuts occurs when the degeneration is not simultaneous, or to the same extent, on the whole wall. The macroscopically observable effects of the degenerations range from dramatic to barely noticeable.
Fabbri, A., Dollo, L., Ferguson, L. and Polito, V.S. (1995). ANATOMICAL STUDIES ON MISSHAPEN PISTACHIO NUTS. Acta Hortic. 419, 73-76