1. Introduction to Coordination in Plants:
   • Plants, like animals, exhibit a form of coordination to respond to their environment and carry out essential functions.
   • Coordination involves the integration of various parts of the plant to achieve proper growth, development, and responses to stimuli.
2. Plant Hormones (Plant Growth Regulators):
   • Hormones are chemical messengers that regulate various plant processes.
   • Key plant hormones include auxins, gibberellins, cytokinins, abscisic acid, and ethylene.
   • Auxins promote cell elongation, control tropisms (growth towards or away from stimuli), and stimulate root formation.
   • Gibberellins stimulate stem elongation, fruit development, and seed germination.
   • Cytokinins promote cell division and delay aging.
   • Abscisic acid regulates stomatal closure, water balance, and stress responses.
   • Ethylene influences fruit ripening, leaf abscission, and responses to mechanical stress.
3. Phototropism and Geotropism:
   • Phototropism is the growth of plant parts towards a light source.
   • Geotropism (gravitropism) is the growth response of plants in relation to gravity, where roots grow downward and shoots grow upward.
4. Role of Hormones in Tropisms:
   • Auxins play a key role in phototropism by accumulating on the shaded side of a stem, causing elongation towards the light.
   • Gibberellins and cytokinins also influence tropic responses.
5. Plant Responses to Environmental Stimuli:
   • Plants respond to various stimuli, including light, gravity, touch, temperature, and water availability.
   • Tropisms are examples of plant responses to stimuli.
6. Role of Phytochromes in Light Sensing:
   • Phytochromes are pigment molecules that enable plants to sense light quality (red and far-red light) and duration.
   • They play a role in controlling processes like seed germination, flowering, and shade avoidance.
7. Plant Movement:
   • Rapid plant movements, such as the closing of Venus flytraps and the folding of Mimosa leaves, are a result of changes in turgor pressure and cell movement.
8. Chemical Coordination and Defense Mechanisms:
   • Plants release chemical signals (volatile organic compounds) in response to herbivores or pathogens to attract predators or discourage pests.
   • Systemic acquired resistance (SAR) is a defense mechanism where a localized response to pathogens triggers a broader immune response throughout the plant.
9. Conclusion:
   • Coordination in plants involves complex interactions between hormones, environmental cues, and cellular processes.
   • Understanding plant coordination helps us appreciate their remarkable adaptability and survival strategies.

Remember to elaborate on these points, provide relevant examples, and encourage critical thinking and discussions in your grade 10 class.

Let’s practice!