ANWSER
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Question 1:
(a) Horticulture is the science and art of cultivating fruits, vegetables, flowers, ornamental plants, and other crops for human use and aesthetic purposes. *(2 marks)*
(b) Water is a critical environmental requirement for plant growth because:
– It is a primary component of photosynthesis, enabling plants to produce food.
– It facilitates nutrient uptake and transport within the plant.
– It maintains turgor pressure, ensuring cell rigidity and plant structure.
– It regulates temperature through transpiration.
– Water is a medium for biochemical reactions in plant cells.
– Drought stress can lead to wilting, stunted growth, and reduced yield. *(8 marks)*
(c) The word “Horticulture” is derived from two Latin words:
– Hortus – meaning “garden”
– Cultura – meaning “cultivation” *(2 marks)*
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Question 2:
(a) Plant growth regulators are natural or synthetic chemicals that influence plant growth and development. *(1 mark)*
(b)
– Biostimulants enhance plant growth by improving nutrient efficiency, stress tolerance, and overall vigor.
– Soil amendments improve soil structure (e.g., compost, peat moss).
– Nutrients provide essential elements (e.g., N, P, K) for plant growth. *(2 marks)*
(c)
(i) Cytokinin functions:
– Promotes cell division and differentiation.
– Delays leaf senescence (aging).
– Stimulates shoot growth.
– Enhances nutrient mobilization.
– Works with auxins to regulate plant morphology. *(5 marks)*
(ii) Auxin functions:
– Promotes cell elongation in stems.
– Regulates apical dominance.
– Stimulates root formation in cuttings.
– Involved in phototropism and gravitropism. *(4 marks)*
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Question 3:
(a)
(i) Sexual propagation: Reproduction through seeds, involving pollination and fertilization. *(2 marks)*
(ii) Asexual propagation: Reproduction using vegetative parts (e.g., cuttings, grafting) without seeds. *(2 marks)*
(b) Disadvantages of sexual propagation:
– Genetic variability (offspring may differ from parents).
– Longer time to maturity.
– Some plants produce few or non-viable seeds.
– Susceptibility to diseases.
Advantages:
– Allows genetic diversity.
– Easier for large-scale production. *(6 marks)*
(c) Disadvantages of asexual propagation:
– No genetic diversity (susceptibility to diseases).
– Requires skilled techniques (e.g., grafting). *(2 marks)*
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Question 4:
(a) Soil animals:
– Earthworms improve soil aeration and nutrient cycling.
– Nematodes can be beneficial (decomposers) or harmful (parasites).
– Insects like beetles aid in organic matter breakdown.
– Microarthropods (e.g., mites) enhance soil structure.
– Burrowing animals (e.g., rodents) mix soil layers.
– Some soil animals spread plant pathogens. *(6 marks)*
(b) Nutrient cycling:
– Decomposition of organic matter releases nutrients (e.g., N, P).
– Microbes and plants participate in biogeochemical cycles.
– Ensures sustainable soil fertility. *(3 marks)*
(c) Soil microbe and plant interactions:
– Rhizobacteria fix nitrogen (e.g., *Rhizobium*).
– Mycorrhizal fungi enhance nutrient/water absorption.
– Some microbes suppress soil-borne diseases. *(3 marks)*
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Question 5:
(a) Soil fertility is the ability of soil to provide essential nutrients for plant growth in proper proportions. *(2 marks)*
(b) Causes of soil fertility loss:
– Erosion (wind/water).
– Overgrazing.
– Deforestation.
– Monocropping.
– Acidification/Alkalization.
– Excessive chemical fertilizer use. *(6 marks)*
(c) Ways to improve soil fertility:
– Crop rotation.
– Organic manure/compost application.
– Cover cropping.
– Liming (for acidic soils). *(4 marks)*
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Question 6:
(i) Simple layering: A low-growing stem is bent to the ground, partially buried, and rooted while attached to the parent plant. *(3 marks)*
(ii) Compound layering: Multiple sections of a stem are alternately buried and exposed to form several new plants. *(2 marks)*
(iii) Tip layering: The tip of a stem is buried to root (e.g., blackberries). *(1 mark)*
(iv) Mound layering: Soil is mounded over the base of a plant to encourage rooting on covered stems. *(3 marks)*
(v) Air layering: A stem section is wounded, wrapped in moist medium (e.g., sphagnum moss), and sealed to promote aerial rooting. *(3 marks)*
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Question 7:
(a) Plant nutrition refers to the uptake and utilization of essential elements for growth, metabolism, and development. *(2 marks)*
(b) Criteria for essential elements:
– Required for normal growth/reproduction.
– Directly involved in plant metabolism.
– Cannot be replaced by another element. *(3 marks)*
(c) Functions of essential elements:
(i) Carbon: Framework for organic molecules (e.g., carbohydrates). *(2 marks)*
(ii) Hydrogen: Component of water and organic compounds; involved in photosynthesis. *(3 marks)*
(iii) Oxygen: Essential for respiration and energy release. *(2 marks)*
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