Tomato Seeds Jumping the Gun
Rosie Lerner, Department of Horticulture and Landscape Architecture, Purdue University
Although not very common, we occasionally get calls regarding tomato fruits that have sprouted seeds inside. Called "vivipary", this premature sprouting of seeds inside the fruit can also happen in peppers and other species.
The "normal" balance of plant growth regulators, notably Abscisic Acid (ABA) inside the fruit should inhibit germination until the seeds have been harvested from the pulp. There may likely be a genetic component, since some commercial canning varieties are more prone to vivipary. However, environmental conditions can also inhibit ABA content. In tomatoes, cool temperatures coupled with low light conditions is thought to inhibit ABA, thus allowing the seeds to germinate inside the moist, warmer environment inside the fruit. Potassium deficiency, over fertilization with nitrogen, and over maturity are also thought to be factors. Fruit that are allowed to get very vine-ripe may be more prone to this.
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Tomato seeds sprouting. Photo courtesy of B. Davis
Tomato seeds sprouting. Photo by Rosie Lerner
Tomato seeds sprouting outside of the fruit
Photo by Roy Ballard