Serotiny

Serotiny in botany simply means 'following' or 'later'.

In the case of serotinous flowers, it means flowers which grow following the growth of leaves,^[1] or even more simply, flowering later in the season than is customary with allied species. Having serotinous leaves is also possible, these follow the flowering.

Serotiny is contrasted with coetany. Coetaneous flowers or leaves appear together with each other.^[1]

In the case of serotinous fruit, the term is used in the more general sense of plants that release their seed over a long period of time, irrespective of whether release is spontaneous; in this sense the term is synonymous with bradyspory.

In the case of certain Australian, North American, South African or Californian plants which grow in areas subjected to regular wildfires, serotinous fruit can also mean 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 used to refer to this specific case.

Possible triggers include:^[2]

• Death of the parent plant or branch (necriscence)
• Wetting (hygriscence)
• Warming by the sun (soliscence)
• Drying atmospheric conditions (xyriscence)
• Fire (pyriscence) — this is the most common and best studied case, and the term serotiny is often used where pyriscence is intended.
• Fire followed by wetting (pyrohydriscence)

Some plants may respond to more than one of these triggers. For example, Pinus halepensis exhibits primarily fire-mediated serotiny,^[3] but responds weakly to drying atmospheric conditions.^[4] Similarly, Sierras sequoias and some Banksia species are strongly serotinous with respect to fire, but also release some seed in response to plant or branch death.

Serotiny can occur in various degrees. Plants that retain all of their seed indefinitely in the absence of a trigger event are strongly serotinous. Plants that eventually release some of their seed spontaneously in the absence of a trigger are weakly serotinous. Finally, some plants release all of their seed spontaneously after a period of seed storage, but the occurrence of a trigger event curtails the seed storage period, causing all seed to be released immediately; such plants are essentially non-serotinous, but may be termed facultatively serotinous.