|While planting some seeds from a grapefruit (freshly eaten) I assumed that they should be dried for a time first but planted them anyway - just to see. I then got to wondering, if they would sprout, why do they not sprout inside the warm, moist medium from which I liberated them? Is there a chemical or enzyme inside the fruit that prohibits seeds from sprouting until they fall to the ground and the flesh rots away? Are the seeds within a ripe fruit mature enough to sprout or do they need to go through a further drying/maturing stage? I know that such seeds as apple need to experience a certain chilling period, but surely not citrus. Just curious.
|Actually, I have seen seeds sprouting inside a citrus fruit once or twice! Citrus seed sprouts readily when fresh and loses its viability as it dries.
You're right--some seeds have a chilling requirement that needs to be met before they'll sprout. Others require a certain amount of further maturation--called after-ripening--before they'll sprout. Still others use chemicals to keep the seeds from sprouting. Tomatoes, for example, will not sprout when taken fresh from the tomato--you need to ferment the seeds and gelatinous matrix to break down the germination-inhibiting substances. (Some tree seeds even need to be scorched by fire to stimulate germination!)
Some seeds have chemicals in the seed coat that inhibit the germination process. In nature, these chemicals are washed away by rain, ensuring a good environment for the young seedlings. Sometimes, a high potassium concentration in the fruit prevents seeds from sprouting. This may be the case with citrus fruits, I'm not sure.