Biology plant and animal response

• What are the two main topics you should understand by the end of this section on plant responses?

  The types of plant responses and the roles of plant hormones
• What happens when an Acacia tree is grazed?

  It releases ethene, causing neighboring plants to produce more tannins as a defense mechanism.
• What are abiotic components in an ecosystem?

  Components that are non-living
• What are alkaloids?

  Organic nitrogen-containing bases that have important physiological effects on animals.
• What are biotic components in an ecosystem?

  Components that are living
• What is a pheromone?

  A chemical substance released by one living thing that influences the behavior or physiology of another living thing.
• What are tannins?

  Phenolic compounds located in cell vacuoles or in surface wax on plants.
• How do plants respond to higher temperatures?

  They may deposit thicker layers of wax on their leaves.
• What is a tropism?

  A directional growth response in which the direction of the response is determined by the direction of the external stimulus.
• What is the role of tannins in plants?

  They are toxic to microorganisms and larger herbivores, making leaves taste bad and preventing root infiltration by pathogens.
• Where are alkaloids found in plants?

  In growing tips, flowers, and peripheral cell layers of stems and roots.
• What are the four types of tropisms mentioned?

  Phototropism, geotropism, chemotropism, and thigmotropism.
• What is phototropism?

  Shoots grow towards light, enabling them to photosynthesize.
• What is geotropism?

  Roots grow towards the pull of gravity, anchoring them in the soil.
• What is chemotropism?

  Pollen tubes grow down the style, attracted by chemicals towards the ovary for fertilization.
• What is thigmotropism?

  Shoots of climbing plants wind around other plants or structures for support.
• What is the difference between a tropic and a nastic response?

  A tropic response is directional, while a nastic response is non-directional.
• What is a thigmonastic response?

  A non-directional response to touch, such as the folding of leaves in *Mimosa pudica*.
• What are cytokinins?

  Plant hormones that promote cell division and delay leaf senescence.
• What do auxins do in plants?

  They promote cell elongation and inhibit the growth of side shoots.
• What is the role of abscisic acid in plants?

  It inhibits seed germination and growth and causes stomatal closure during low water availability.
• What is the function of gibberellins?

  They promote seed germination and stem growth.
• How does ethene affect fruit and flower aging?

  It promotes fruit ripening and the aging of flowers.
• How do plant hormones coordinate responses to environmental stimuli?

  They act as chemical messengers transported to target cells or tissues in the plant.
• How do hormones move around the plant?

  Through active transport, diffusion, or mass flow in phloem sap or xylem vessels.
• Why do only certain tissues in a plant respond to a particular hormone?

  Because specific hormones bind to specific receptors on the plasma membrane of target cells.
• What is apical dominance?

  The inhibition of lateral buds by chemicals produced by the apical bud at the tip of a plant shoot.
• How do auxins affect lateral bud growth?

  High auxin levels inhibit growth, while low auxin levels promote growth.
• What is the role of amylase during seed germination?

  It breaks down starch into glucose, providing energy for the embryo.
• What is the effect of gibberellins on dwarf plants?

  They cause dwarf plants to grow taller when applied.
• How do gibberellins promote seed germination?

  By enabling the production of amylase, which breaks down starch into glucose for the embryo.
• What is the significance of meristems in plants?

  They are groups of immature cells capable of dividing, responsible for plant growth.
• Where are apical meristems located?

  At the tips of roots and shoots.
• What do lateral meristems do?

  They are responsible for the roots and shoots getting wider.
• What is the function of intercalary meristems?

  They are responsible for growth between the nodes, allowing the shoot to get longer.
• How can phototropic responses be investigated?

  Through controlled experiments that observe plant growth towards light sources.
• How does the walking palm tree adapt to its environment?

  It grows new roots towards sunny patches, pulling the stem and leaves towards the light.
• What is geotropism?

  A directional growth response to gravity.
• What is the significance of auxins in apical dominance?

  They prevent lateral buds from growing when present in high levels.
• How do researchers confirm the role of gibberellins in stem elongation?

  By comparing gibberellin levels in tall and dwarf plants and observing growth responses.