bradyspory is the gradual release of seed from a cone

Conifer cone

A cone is an organ on plants in the division Pinophyta that contains the reproductive structures. The familiar woody cone is the female cone, which produces seeds. The male cones, which produce pollen, are usually herbaceous and much less conspicuous even at full maturity...

 or fruit

Fruit

In broad terms, a fruit is a structure of a plant that contains its seeds.The term has different meanings dependent on context. In non-technical usage, such as food preparation, fruit normally means the fleshy seed-associated structures of certain plants that are sweet and edible in the raw state,...

 over a long period of time, as opposed to tachyspory, the more-or-less immediate release of seed as soon as they have matured.

Bradyspory may occur because seed release is spontaneous but very gradual, or because seed release does not occur until triggered to do so by some environmental event. The latter case is termed serotiny

Serotiny

Serotiny is an ecological adaptation exhibited by some seed plants, in which seed release occurs in response to an environmental trigger, rather than spontaneously at seed maturation. The most common and best studied trigger is fire, and the term serotiny is often used to refer to this specific case...

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