Grade 10 general science – Plant growth and development Quiz
1. Which process in plants converts light energy into chemical energy stored as sugars?
Photosynthesis is the process by which plants use light energy, carbon dioxide and water to produce sugars and oxygen. Respiration breaks down sugars, transpiration is water loss, and nitrogen fixation converts atmospheric nitrogen to usable forms.
2. What is the main function of root hairs in young maize or bean plants grown in Kenyan farms?
Root hairs are tiny extensions of root epidermal cells that increase surface area, improving uptake of water and dissolved minerals from the soil.
3. During seed germination, which of the following is the first event for most seeds like maize after they absorb water?
After water uptake (imbibition), the radicle usually emerges first to anchor the seedling and absorb water and nutrients, allowing further growth of shoot and leaves.
4. Which plant hormone is mainly responsible for promoting stem elongation and growth in young seedlings?
Auxins stimulate cell elongation in stems and are important for phototropism and apical dominance. Ethylene affects ripening, abscisic acid promotes dormancy, and cytokinins promote cell division.
5. What is phototropism in plants?
Phototropism is directional growth in response to light, commonly seen when shoots bend toward light due to unequal distribution of auxin.
6. Which stage comes immediately after pollination in flowering plants such as tea or coffee?
After pollination (transfer of pollen to the stigma), fertilisation occurs when sperm from pollen fuses with the ovule to form a zygote, leading to seed development.
7. Which mineral nutrient is most directly needed for strong stems and seeds and is commonly applied as phosphate fertilizer to Kenyan soils?
Phosphorus is important for energy transfer, root development and seed formation; phosphate fertilizers supply phosphorus to soils where it is limiting.
8. What role do guard cells play in a leaf?
Guard cells change shape to open or close stomatal pores, regulating carbon dioxide uptake for photosynthesis and water loss through transpiration.
9. Which environmental factor most directly affects the rate of transpiration in plants on a hot, dry Kenyan afternoon?
Transpiration rate increases with higher temperature and lower humidity because the water vapour gradient between leaf and air becomes larger; soil pH and root length are less directly influential on immediate transpiration.
10. What is photoperiodism and why is it important for Kenyan farmers growing short-day crops?
Photoperiodism is how plants detect daylength to time flowering. Short-day crops flower when nights are long; understanding this helps farmers in timing planting for local rainy seasons.
11. Which structure transports sugars produced in leaves to other parts of the plant such as roots and developing fruits?
Phloem conducts dissolved sugars (products of photosynthesis) from leaves to sinks like roots, shoots and fruits; xylem mainly transports water and minerals upward.
12. Why is crop rotation practiced by farmers in Kenya?
Rotating different crops helps restore nutrients (e.g., legumes add nitrogen), breaks pest and disease cycles, and maintains soil health for sustained yields.
13. What is the main purpose of pruning fruit trees like mango or avocado in Kenyan orchards?
Pruning removes excess branches to allow more light and air into the canopy, reducing disease and improving fruit development and harvestability.
14. Which of the following best explains why seeds are dispersed away from the parent plant?
Dispersal helps offspring establish where resources are available and reduces competition with the parent, improving survival chances.
15. How does adding compost to farm soil help plant growth?
Compost adds organic matter that enhances soil texture, increases the soil’s ability to hold water and nutrients, and supplies slow-release nutrients for plants.
16. Which gas is taken in by leaf stomata for photosynthesis and which gas is released as a major by-product?
During photosynthesis, plants take in carbon dioxide from the air and produce oxygen as a by-product while forming sugars.
17. What is the primary function of mycorrhizal fungi associated with plant roots in Kenyan soils?
Mycorrhizae form mutualistic associations with roots, extending the effective root area to access water and nutrients (especially phosphorus) while receiving carbohydrates from the plant.
18. Which agricultural practice helps conserve soil moisture and reduce erosion on sloping farmland in Kenya?
Terracing reduces slope steepness and runoff, and mulching covers soil to retain moisture and protect against erosion; burning and removing cover increase erosion risk.
19. Why do some plants like certain sorghum varieties close their stomata during the hottest part of the day?
Closing stomata limits water loss when evaporative demand is high, helping the plant conserve water though it reduces CO2 uptake and photosynthesis temporarily.
20. What causes phototropism, the bending of plant shoots toward light?
Auxin accumulates on the shaded side of a shoot, promoting cell elongation there so the shoot bends toward the light source.
21. Which condition would most likely break seed dormancy and allow germination of many crop seeds?
Seeds require water to rehydrate metabolic systems, oxygen for respiration and a suitable temperature to activate enzymes; without these, dormancy persists.
22. What is the effect of applying too much nitrogen fertilizer to a vegetable crop?
High nitrogen encourages vegetative (leaf) growth, which can reduce flowering and fruiting and may cause imbalances and increased susceptibility to pests and lodging.
23. Which adaptation helps plants survive in waterlogged soils common in some parts of flood-prone Kenyan lowlands?
Aerenchyma are air-filled spaces in roots and stems that permit diffusion of oxygen from shoots to roots, helping plants survive low-oxygen waterlogged conditions.
24. How does salinity in soil affect plant growth often seen in irrigated fields?
High salt concentration in soil makes it harder for roots to take up water (osmotic stress) and can lead to ion toxicity, leaf scorch and reduced growth.
25. Which method best demonstrates an experiment a Form 3 Kenyan student can do to investigate the effect of light on plant growth?
This controlled experiment isolates light as the variable; using identical seedlings and conditions except for light allows comparison of its effect on growth metrics.
26. Why is nitrogen fixation by legume roots important in sustainable farming systems in Kenya?
Rhizobium bacteria in legume root nodules convert atmospheric nitrogen into forms plants can use, improving soil fertility and lowering fertilizer costs.