Plant Hormone Crosstalk in Reproduction

Summary

Interacting auxin, gibberellin and cytokinin signals control flower, fruit and seed development.

In depth

Gibberellin and auxin trigger fruit set; ethylene triggers ripening; ABA and GA balance seed dormancy. Parthenocarpic (seedless) fruits form with applied hormones.

Hormone balance determines flowering time, fruit set and seed maturation. Commercial use includes fruit thinning and ripening.

Key idea: plant reproduction depends on interacting hormones.

Plant reproduction is coordinated by interacting hormones. Gibberellins promote flowering in some long-day plants and seed germination, auxin from developing seeds stimulates fruit growth, cytokinins promote cell division in ovules and fruits, abscisic acid induces seed dormancy, and ethylene triggers fruit ripening and senescence.

Interactions are often antagonistic or synergistic: GA and ABA oppose each other in germination; auxin and cytokinin ratios control shoot versus root formation; florigen (the FT protein) moves from leaves to the shoot tip to start flowering. Without pollination, auxin sprays can produce seedless fruit (parthenocarpy).

Example: ethylene in one ripe apple speeds ripening of others in a bowl.

Key idea: development depends on hormone balance, not a single hormone.