Growth in Plants Meristems

Growth in Plants Meristems Define meristems Meristems are undifferentiated cells in plants capable of indeterminate growth (analogous to stem cells) ………………………………………………………………………………………………………………………………………………….......... Meristematic tissues have specific regions of growth in plants (allows regrowth or vegetative propagation) ………………………………………………………………………………………………………………………………………………….......... Compare growth due to apical and lateral meristems Apical Meristems Occurs at the tips of roots and shoots ………………………………………………………………………… Responsible for primary growth (adds length) ………………………………………………………………………… Develops into primary xylem and phloem ………………………………………………………………………… Produces new leaves and flowers ………………………………………………………………………… Lateral Meristems Occurs at the cambium ………………………………………………………………………… Responsible for secondary growth (adds width) ………………………………………………………………………… Produces secondary xylem and phloem ………………………………………………………………………… Produces the bark on trees ………………………………………………………………………… Plant Signalling Identify one function of each of the following plant hormones Involved in primary growth and tropic responses Auxin: …………………………………………………………………………………………………………………………………………….. Involved in seed germination Gibberellin: …………………………………………………………………………………………………………………………………….. Involved in secondary growth (e.g. branching) Cytokinin: ………………………………………………………………………………………………………………………………………. Responsible for abscission and regulating transpiration Abscisic Acid: ………………………………………………………………………………………………………………………………….. A gas which stimulates ripening Ethylene: ………………………………………………………………………………………………………………………………………… Describe the role of auxin in apical dominance Auxin released by the apical meristem in shoots promotes apical growth (verticality) ………………………………………………………………………………………………………………………………………………….......... It additionally inhibits growth in lateral buds (a condition called apical dominance) ………………………………………………………………………………………………………………………………………………….......... As shoots grow further from lateral buds, inhibition is diminished, allowing spread ………………………………………………………………………………………………………………………………………………….......... Outline how auxin concentration gradients may be established within plant tissue Auxin efflux pumps set up concentration gradients of auxin in response to stimuli ………………………………………………………………………………………………………………………………………………….......... These pumps control growth direction by determining areas with high auxin levels ………………………………………………………………………………………………………………………………………………….......... Tropisms Define tropism and give two specific examples Tropism is the turning of an organism in response to a directional external stimulus ………………………………………………………………………………………………………………………………………………….......... Phototropism: Growth response to light 1. …………………………………………………………………………………………………………………………………………………... Geotropism: Growth response to gravity 2. …………………………………………………………………………………………………………………………………………………... With the aid of the diagram, explain the role of auxin in phototropism in shoots and roots Plant tropisms are caused by a differential elongation of cells in response to stimulus ………………………………………………………………………………………………………………………………………………….......... Auxin controls growth rates by changing patterns of gene expression in plant cells ………………………………………………………………………………………………………………………………………………….......... In shoots, auxin promotes cell elongation, whereas in roots, auxin inhibits cell elongation ………………………………………………………………………………………………………………………………………………….......... Plant turns away from side with cell elongation, so the shoots grow towards light (positive tropism) ………………………………………………………………………………………………………………………………………………….......... and the roots grow away from light (negative tropism) ………………………………………………………………………………………………………………………………………………….......... Describe the process of micropropagation and provide three examples of potential applications The process of micropropagation involves: ………………………………………………………………………………………………………………………………………………….......... 1. Tissue sample (explant) grown in nutrient agar 2. Development prompted by growth hormones 3. Growing shoots divided (multiplication phase) 4. Cloned plants transferred to new soil ………………………………………………………………………………………………………………………………………………….......... ………………………………………………………………………………………………………………………………………………….......... Rapid bulking: Cloning desirable stock plants 1. …………………………………………………………………………………………………………………………………………………... Virus-free strains: Cloning non-infected tissue 2. …………………………………………………………………………………………………………………………………………………... Propagating rare species: Prevents extinction 3. …………………………………………………………………………………………………………………………………………………...