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How do different auxin and cytokinin levels affect roots and shoots in tissue culture?
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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.
In horticultural tissue culture, the relative concentrations of auxin and cytokinin are critical for determining the developmental pathway of plant cells. These hormones work in conjunction to regulate cell division and cell differentiation.12
The specific effects of these hormone levels are as follows:
- Root Development: Conditions characterized by high auxin and low cytokinin levels promote the formation of roots.1
- Shoot Development: Conversely, low auxin and high cytokinin levels encourage the development of shoots.1
By manipulating the ratio of these two hormones, researchers can effectively control the morphogenesis of plant tissues in a laboratory setting.1