Cytokinin Activity in Avocado Seeds during Fruit Development.

The soybean callus bioassay was used to determine levels of cytokinin activity in avocado (Persea americana) seeds.In the embryo, levels are high during the early stages of development, but diminish as the fruit grows. The level of cytokinin activity in the endosperm is very high throughout the period that this tissue exists. The seed coats have very high activity levels while the fruit is young, reaching values comparable with those found in the endosperm. The activity level falls as the rate of fruit growth slows down and disappears completely by the time the seed coats shrivel at approximately the same time the fruit reaches "horticultural maturity".