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How do cytokinins delay leaf yellowing during senescence?
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plant development
The life cycle of the fern. (1) Clusters (sori) of sporangia (spore cases) grow on the undersurface of mature fern leaves. (2) Released from its spore case, the haploid spore is carried to the ground, where it germinates into a tiny, usually heart-shaped, gametophyte (gamete-producing structure), anchored to the ground by rhizoids (rootlike projections). (3) Under moist conditions, mature sperm are released from the antheridia and swim to the egg-producing archegonia that have formed on the gametophyte's lower surface. (4) When fertilization occurs, a zygote forms and develops into an embryo within the archegonium. (5) The embryo eventually grows larger than the gametophyte and becomes a sporophyte.
Cytokinins delay leaf yellowing during senescence by acting as a preservative mechanism for the leaf's internal components. Senescence is an organized metabolic process characterized by the breakdown of proteins and the destruction of chlorophyll, which leads to the characteristic yellowing of leaves.12
Cytokinins prevent this degradation by performing the following functions:
- Stabilizing Content: They maintain the levels of protein and chlorophyll within the leaf tissue.12
- Preserving Structure: They protect the structural integrity of chloroplasts, the organelles responsible for photosynthesis.12
Because of these properties, cytokinins are utilized commercially in the storage of green vegetables to extend their shelf life and maintain their green appearance.12