Occasionally, we see some strange and fascinating things in the plant world which may leave us wondering what has possessed our plants. A couple of weeks ago I happened to find a good example of one of these while picking strawberries. You may have also seen something similar in your fruits or vegetables before and not realized what was going on. No need to fear though, it is not a supernatural phenomenon at work.
The strawberry in question had tiny green sprouts emerging from the “seeds” covering the fruit. Right away I recognized this as a great example of vivipary. While it is common to occasionally see this in strawberries, I believe I’ve only seen it before in tomatoes, peppers, apples, pumpkins and maybe one or two oranges. You’ve probably seen this before when slicing a tomato. I know I usually see it in one or two each spring. While it may look alarming, vivipary is a normal plant response to a lack of a specific hormone.
Fruits are responsible for producing seeds for continual propagation of a plant. A fruit is the mature, ripened ovary and/or other parts of the flower of a plant that is responsible for protecting and dispersing seeds. Over time, humans have bred plants such as tomatoes, peppers, pumpkins, strawberries, corn and others to produce more desirable fruit and/or seeds that we use as food.
In the case of strawberries, the edible portion that we call the fruit is the swollen flower receptable that holds many achenes. We typically refer to achenes as strawberry seeds. This is partially true, as achenes are the true fruits of the strawberry. These dry fruits each contain a seed. They are attached to the flower receptable that develops into a juicy, sweet aggregate accessory fruit.
Plants, like us, have different hormones responsible for growth and development. Two plant hormones, abscisic acid (ABA) and gibberellic acid, regulate seed dormancy. ABA inhibits growth and germination. Gibberellic acid promotes seed germination.
High moisture levels in fruit can lead to lower ABA levels. When this happens, seed germination inside the fruit can occur. Occasionally you will see this in corn when high levels of moisture get trapped under the husks. Fruits that have been held in storage for lengthy periods can also exhibit vivipary simply because the hormone supply inhibiting seed germination has ran out. I’ve seen this before in apples that I’ve kept in my refrigerator for several weeks.
Vivipary is a Latin term meaning ‘live birth’. Normally, seeds germinate after the fruit or parent plant dies, or the seed is released from the fruit either by animals feeding on the fruit or some other method of disbursement. There are some plants though that purposely signal seeds to germinate while still attached to the mother plant.
In certain climates like Alpine, because of short growing seasons, or marshes, because of semi-aquatic conditions, this is a developmental advantage. The Alpine plant, Bistorta vivipara, and marsh mangroves are both examples of plants that exhibit vivipary to ensure seedling survival. You may have seen vivipary on a common houseplant called Kalanchoe. They will produce plantlets along leaf edges.
Perhaps you have thrown out tomatoes, peppers, or apples before when you have seen vivipary in their seeds thinking the fruit was bad or diseased. Assuming the fruit is not rotten or dried out, fruits exhibiting vivipary are safe to eat. You can simply remove the sprouted seeds. In the case of the strawberry with vivipary, I just threw it out, but not before taking a picture!
