Test: Chemical Coordination in Plants - Class 10 MCQ

Gibberellins play a critical role in stimulating shoot elongation during seed germination. They help break dormancy and promote the growth of seedlings, ensuring that plants can emerge effectively from the soil and access sunlight.

Hydrotropism benefits plants by directing roots towards moisture sources in the soil. This response is essential for ensuring that plants can access the water necessary for survival, particularly in arid environments where water is limited.

Auxins generally inhibit root growth when applied in high concentrations, which is why they are used in horticulture to promote rooting in cuttings. Understanding this balance is crucial for effective plant propagation techniques.

Auxins promote fruit growth by stimulating cell elongation and division. They play a significant role in the development of fruits, ensuring that they mature properly and contribute to the plant's reproductive success.

Abscisic acid serves as a growth inhibitor, promoting dormancy in seeds and buds. It also plays a role in closing stomata to reduce water loss during stress conditions. This hormone is critical for helping plants survive adverse environmental conditions.

Gibberellins are involved in breaking seed dormancy and promoting seed germination. They stimulate growth and elongation in shoots, helping plants transition from a dormant state to an active growth phase, which is crucial for successful reproduction and survival.

Thigmotropism is associated with the movement of plants in response to physical contact with solid objects. This response is particularly beneficial for climbing plants, allowing them to secure themselves as they grow towards sunlight.

Shoots exhibit positive phototropism by growing towards the light source. This adaptive response enhances photosynthesis and allows plants to maximize their energy intake, which is crucial for growth and survival.

Cytokinins play a vital role in delaying the aging of leaves. By promoting cell division and growth, these hormones help maintain leaf vitality, which is essential for continuous photosynthesis and overall plant health.

Chemotropism is defined as the movement of plant organs in response to chemical stimuli. It can be positive, where growth occurs towards a chemical, or negative, where growth occurs away from it, as seen in various plant responses to nutrients or toxins.

Auxins are primarily known for promoting plant growth. They are produced in the tips of stems and roots and stimulate cell elongation, which is crucial for the overall development of the plant. This hormone is also utilized in horticulture to encourage growth in various plants.

Thigmotropism refers to the movement of plant organs in response to physical contact with solid objects. This is particularly evident in climbing plants that use tendrils or twining stems to support themselves, allowing them to reach sunlight more effectively.

Geotropism is the movement of plant organs in response to gravity. Roots are positively geotropic, growing downwards towards gravity, while shoots are negatively geotropic, growing upwards against it. This response helps ensure that roots anchor the plant and access water and nutrients from the soil.

Cytokinins are known for their role in promoting cell division in plants. They also have other vital functions, such as delaying leaf aging and stimulating fruit growth. Understanding the role of cytokinins helps in improving agricultural practices, particularly in enhancing crop yields.

Sunflowers exhibit heliotropism by bending towards the sun. This movement is facilitated by auxins, which promote growth on the shaded side of the stem, allowing the flower to maximize sunlight exposure and enhance photosynthesis, vital for their growth and reproduction.

Pollen tubes exhibit positive chemotropism by growing towards the sugary substances secreted by the stigma of flowers. This movement is essential for successful fertilization, as it directs the pollen tubes to the ovule for reproduction.

Phototropism refers to the movement of plant parts towards light. This adaptive response allows plants to maximize their exposure to sunlight, essential for photosynthesis. Most shoots exhibit positive phototropism, growing towards the light source, while roots demonstrate negative phototropism, growing away from it.

Hydrotropism describes the movement of plant organs in response to water. Roots grow towards moisture, which is essential for the plant's survival as it helps ensure access to water necessary for various physiological processes.

When abscisic acid levels increase, it causes the stomata to close, reducing water loss through transpiration. This response is vital during drought conditions, helping plants conserve water and survive in stressful environments.

Roots respond positively to gravity, growing downwards in the direction of gravitational pull. This geotropic response is crucial for anchoring the plant and optimizing nutrient and water uptake from the soil.