Plant Responses: Types, Hormones, and Commercial Uses

• Plant Responses

  Plants have evolved various responses to stimuli in order to survive and reproduce.
• Survive


  The ability of plants to continue living and avoid death.
• Reproduce


  The process by which plants produce offspring or new individuals of the same species.
• Avoid predation


  The ability of plants to escape or prevent being eaten by predators.
• Abiotic stress


  Stress caused by non-living factors in the environment, such as temperature, light, or chemicals, that affects plant growth and survival.
• Chemical defenses


  Chemical compounds produced by plants to deter herbivores, such as tannins, alkaloids, and pheromones.
• Folding in response to touch


  The ability of certain plants, like Mimosa pudica, to fold or close their leaves or petals when touched.
• Tropisms


  Directional growth responses in plants to external stimuli.
• Phototropism


  The positive or negative growth response of plants towards or away from light, respectively.
• Geotropism


  The positive or negative growth response of plants towards or away from gravity, respectively.
• Chemotropism


  The growth response of plants towards or away from specific chemicals.
• Thigmotropism


  The growth response of plants towards or away from touch or physical contact.
• Nastic movements


  Rapid plant movements in response to external stimuli, such as changes in turgidity in cells.
• Venus flytrap


  An example of a nastic movement where the trap shuts rapidly in response to prey.
• Phototropins


  Proteins that act as receptors for blue light in certain plant cells, involved in phototropism.
• Coleoptiles


  Sheath protecting the embryonic shoot in grasses, used in experiments on phototropism.
• Auxin


  A plant hormone that promotes stem elongation, stimulates cell division, prevents leaf fall, and maintains apical dominance.
• Gibberellin


  A plant hormone that elongates internodal regions of stems, breaks seed dormancy, and mobilizes food stores for growth.
• Cytokinin


  A plant hormone that delays leaf senescence, promotes cell division, and stimulates growth of lateral buds.
• Abscisic Acid


  A plant hormone that inhibits growth, controls stomatal closure, and plays a role in leaf abscission.
• Ethene


  A plant hormone that promotes ripening of fruits, stimulates seed germination, and is involved in abscission.
• Apical dominance


  The suppression of lateral bud growth by auxin produced in the apical meristem.
• Phytochrome


  A plant pigment that exists in two forms and regulates plant responses to day length.
• Stomatal closure


  The process of closing stomata in response to water stress, controlled by abscisic acid.
• Leaf abscission


  The process of leaves falling off plants, controlled by abscisic acid and ethene.
• Selective herbicides


  Synthetic auxins used to kill weeds without harming desired plants.
• Parthenocarpy

  The formation of fruit without fertilization, induced by auxin application.
• Rooting powders


  Hormone-containing powders applied to plant cuttings to stimulate root growth.
• Ripening


  The process of fruit becoming mature and ready for consumption, promoted by ethene.
• Hormonal weed killers

  Herbicides that mimic plant hormones to disrupt weed growth and development.
• Seed dormancy


  The condition in which seeds do not germinate even under favorable conditions, controlled by hormones.
• Phytochrome Pr


  The inactive form of phytochrome, which exists in darkness or when exposed to far red light.
• Phytochrome Pfr


  The active form of phytochrome, formed when exposed to red light during daylight hours.
• Long day plants


  Plants that require longer days and shorter nights to flower, such as petunias.
• Short day plants


  Plants that require a critical length of night to flower, such as some orchids.
• Leaf senescence


  The process of aging and deterioration in leaves, delayed by cytokinins.
• Herbivory


  The consumption of plant tissues by herbivores.