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How does water absorption trigger seed germination?
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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.
Water absorption, or imbibition, is the critical first step in triggering seed germination. When a seed is exposed to appropriate environmental conditions, it absorbs water, which leads to the rehydration and physical expansion of the cells within the embryo.12
This uptake of water initiates several vital physiological changes:
- Metabolic Resumption: Shortly after imbibition begins, the rate of respiration increases, and various metabolic processes that were suspended or significantly reduced during dormancy resume.12
- Structural Changes: The influx of water is associated with structural modifications in the organelles, which are the cellular components responsible for metabolism.12
- Inhibitor Removal: In some cases, water also serves to leach away chemical inhibitors that prevent germination, allowing the embryo to begin its growth.12
Once these processes are underway, the embryo transitions from a dormant state to active growth, typically marked by the emergence of the primary root, or radicle.1