A reduction in light reaching the fruiting zone can have two effects on fruit quality. The first is a reduction in the photosynthesis of leaves associated with the fruit and subsequent reduction in the transport of sugars to the fruit. The second effect is to reduce thermal conditions surrounding the fruit. This is of particular importance under New Zealand conditions, as air temperatures during the growing season may be marginal for persimmon production. Fruit exposed to light can have a fruit temperature 5 o C above air temperature in comparison with shaded fruits which can be 2 o C below.
Thermal conditions are important in controlling the rate of astringency loss from fruit.
The acetaldehyde reacts with soluble tannins to remove astringency from the fruit. Under cooler conditions, acetaldehyde accumulation occurs at a slower rate causing incomplete astringency removal. Thermal conditions may also influence fruit weight. This effect was highlighted in an experiment in our study where exposed and unexposed fruit, adjacent in the canopy, were compared. The fruit weights were 310 and 230g, for exposed and unexposed fruit respectively.