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Timing of senescence: The opening act

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  1. Introduction.
  2. Genotypes.
  3. Carbohydrates.
    1. Significant changes in carbohydrate levels.
    2. Recent work in arabidopsis thaliana.
  4. Circadian rhythms.
  5. Interorgan communication.
    1. Timing of senescence of petals and corollas.
    2. Styles in triggering age-related flower senescence.
  6. Abiotic stresses.
  7. Pollination.
  8. Hormones.
  9. Conclusion.

Flower senescence in this context will happen when it becomes more advantageous for the plant to construct a new flower ? including renewed odds of getting pollinated ? than to maintain an existing one. Flower senescence can therefore be defined as the events that lead to the death of flower parts signaling the end of an open and functional disseminator and/or receptor of pollen. It should be noted here that the most visible and largest flower part to senesce is the corolla or petals and that this organ will receive most attention in this chapter. However, other flower parts such as styles, anthers, and in the case of unpollinated flowers, ovaries, sepals and pedicels, will also in time senesce.

[...] Therefore, recognition of self and non-self pollen, and the rejection of self is essential in pollination-induced senescence. Although the early events, generally a small ethylene peak produced by the style, are the same in either type of pollination, further ethylene production is non-existent in self- incompatible pollinations. This observation indicates that complex recognition and rejection signals beyond ethylene are at play. Hormones All classical hormones, cytokinin, ABA, gibberellins, auxins and ethylene, have at one point or another been implicated in timing of flower senescence and their individual roles and possible interactions have not, by far, been settled. [...]

[...] The overall conclusion of these studies was that flower longevity can be significantly improved through classical breeding efforts often because improvements in flower longevity have not been focused on before. Carbohydrates Significant changes in carbohydrate levels can be observed throughout the development of petals and corollas. In most petals and corollas, starch, sucrose and a number of other sugars decline after anthesis in both cut and uncut. However, relatively high levels of sugars are maintained through senescence in several species. [...]

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