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Flower senescence

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  1. Introduction.
  2. Categories of flower senescence.
    1. Age related versus pollination induced.
    2. Ethylene sensitive versus ethylene insensitive.
    3. Abscised versus persistent petals.
  3. From anthesis to senescence: Setting the stage.
    1. Physiological changes.
    2. Biochemical changes.
    3. Molecular changes.
  4. Conclusion.

Flowers, no matter their size, shape, color or structure, have one important function for plants: sexual reproduction. Sexual reproduction consists of several distinct developmental processes including pollen production, ovule formation, and pollination, fusion of gametes and the development and dispersal of viable seeds. Many flowers have the additional function of attracting pollinators. The initial attraction between flowers and their pollinators can be the result of petal or corolla color or shape, or chemical composition of the flower, whereas the end of a flower's attraction to pollinators is the result of petal or corolla in rolling or closure, color changes, changes in chemical composition of flower scent or nectar, and ultimately withering or abscission of the petals. Therefore, pollination and subsequent changes in the flower corolla can be seen as a way of communication between the flower and pollinators.

[...] A lipoxygenase- independent senescence mechanism has been described in Alstroemeria peruviana, somewhat similar to the observations made in orchids where increases in lipoxygenase activity were absent following pollination. However, in this species lipoxygenase activity declined significantly throughout petal development and did not increase leading up to senescence. This is in contrast to some other ethylene-sensitive and -insensitive species where lipoxygenase activity peaks at early to midsenescent stages of development. In Alstroemeria, an ethylene-insensitive species, lipoxygenase activity could not be correlated with the loss of membrane semipermeability indicating that it falls into a new class of flower senescence. [...]

[...] Molecular changes Very little attention has been given to molecular changes from anthesis through senescence with the exception of one recent study. Most genes isolated from petals or corollas of ethylene-sensitive and insensitive species have been cloned from early to mid-senescent plant materials. Therefore, most of the transcripts of these genes are found to accumulate during senescence and not in the events leading up to senescence. A few of these genes have shown developmental regulation independent of senescence in both ethylene-sensitive and insensitive species, even though their highest transcript levels are observed during senescence. [...]

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