Plant Growth and Development
Analyze why cells in the meristematic phase of growth are typically rich in protoplasm and possess large, conspicuous nuclei.
Define the term 'growth' as it applies to living organisms.
Analyze why viable seeds stored in a cool, dry container often fail to germinate, entering a state of dormancy.
A root is observed to be elongating at a constant rate, exhibiting arithmetic growth. If its initial length at time zero () was cm and its growth rate () is cm per day, calculate its final length () after 6 days.
Identify the plant growth regulator that exists as a gas.
Name the synthetic auxin widely used as a herbicide to kill dicotyledonous weeds.
A sugarcane farmer wishes to increase the yield of sugar, which is stored in the stems. Apply your understanding of phytohormones to recommend a treatment that would increase the length of the sugarcane stems.
Name the five major groups of naturally occurring plant growth regulators.
Critique the use of the term 'growth' to describe the swelling of a dry piece of wood when placed in water. Is it true growth? Justify your answer.
Recall the scientist who first isolated auxin from the tips of oat seedlings.
A farmer has harvested a large quantity of green bananas and needs to ripen them uniformly before sending them to the market. Apply your knowledge of plant growth regulators to suggest which gaseous hormone should be used and why.
Examine the statement 'differentiation in plants is open'. Provide an example of how the final structure of a cell is determined by its location within the plant body.
A gardener wants to create a very dense, bushy hedge from a row of young plants that are growing tall and thin. Analyze the phenomenon responsible for this growth pattern and demonstrate the horticultural practice that should be applied to achieve the desired bushy growth.
Evaluate the statement: 'For any developmental event in a plant, such as seed dormancy, only one Plant Growth Regulator is responsible.' Use the examples of ABA and Gibberellins to support your evaluation.
Explain the concept of 'apical dominance' and name the plant hormone primarily responsible for it.
Describe the three distinct phases of growth observed in a plant root tip.
Define 'plasticity' in the context of plant development.
Describe the phenomenon of 'redifferentiation' with an example from a woody dicotyledonous plant.
Demonstrate how growth is measured differently in a dorsiventral leaf compared to a pollen tube, and analyze why a single parameter is insufficient to measure growth in all plant parts.
Critique the statement: 'Ethylene is exclusively a growth-inhibiting hormone.' Justify your position with specific examples of its promotory effects.
You are given a plant exhibiting a rosette habit (e.g., cabbage) and need to induce flowering for seed production. Design a treatment plan using a specific plant growth regulator, justifying your choice and describing the expected morphological change.
Explain why Abscisic Acid (ABA) is commonly referred to as the 'stress hormone'.
Describe how ethylene is used in agriculture to regulate fruit ripening and flowering. Mention the compound commonly used as a source of ethylene.
Compare and contrast arithmetic and geometric growth in plants, referencing their defining characteristics, mathematical expressions, and the shape of their respective growth curves when plotted against time.
Examine heterophylly in buttercup as an example of plasticity. How does this phenomenon demonstrate the influence of the environment on plant development?
A potted plant is accidentally left without water for several days during a hot, dry period. Analyze the immediate physiological response the plant would initiate to conserve water, and identify the specific plant hormone responsible for this 'stress' response.
Contrast the roles of auxin and ethylene in the process of abscission (the shedding of leaves and fruits).
Justify why abscisic acid (ABA) is aptly termed the 'stress hormone'. Provide at least two distinct examples of its role in helping plants cope with environmental stress.
Propose why the sigmoid (S-shaped) growth curve is a more accurate representation of the growth of an organ like a fruit, compared to a simple arithmetic growth model.
Two leaves, P and Q, have initial areas of and respectively. In a span of one week, both leaves increase their area by . Evaluate which leaf exhibits a higher relative growth rate and justify your answer with calculations.
A gardener uses 2,4-D to remove broad-leaved weeds from a lawn of monocot grass. Evaluate the selectivity of this chemical and propose a reason for its differential effect on dicots versus monocots.
Formulate a reason why the processes of dedifferentiation and redifferentiation are crucial for a plant's ability to recover from injury.
A farmer notices that their cucumber plants are producing an overwhelmingly high number of male flowers, leading to poor fruit yield. Propose a treatment using a specific Plant Growth Regulator (PGR) to solve this problem and justify your choice.
Propose a physiological mechanism explaining how auxins, produced in the apical bud, maintain apical dominance. Then, explain how cytokinins, produced in the roots, can counteract this effect.
Formulate a comprehensive strategy for a commercial horticulturist to delay the senescence of cut flowers and leafy vegetables post-harvest, thereby extending their shelf life. Justify the choice of Plant Growth Regulator (PGR) for this purpose.
A student sets up a plant tissue culture experiment using tobacco stem segments on a nutrient medium containing auxins. After several weeks, the callus (a mass of undifferentiated cells) fails to proliferate into new plantlets. Analyze the likely reason for this failure and solve the problem by suggesting what must be added to the culture medium.
Two leaves, Leaf P and Leaf Q, were observed over a period of one week. Leaf P grew from an initial area of to a final area of . Leaf Q grew from an initial area of to . Calculate and compare the absolute and relative growth rates for both leaves to determine which leaf grew faster in relative terms.
Evaluate the concept of 'open differentiation' in plants. Justify how this phenomenon, linked to the position of cells, contributes to the structural and functional complexity of a plant body.
Explain the difference between absolute growth rate and relative growth rate.
Create a hypothesis to explain why spraying juvenile conifers with gibberellins () leads to early seed production.
Summarize the discovery of cytokinins, mentioning the key scientists and the sources from which cytokinin-like substances were identified.
List five physiological effects of gibberellins and describe their application in the sugarcane and brewing industries.
A horticulturist needs to perform three tasks: (a) induce 'bolting' in a rosette plant like cabbage, (b) induce rooting in stem cuttings, and (c) promote the development of female flowers in cucumbers to increase yield. Apply your knowledge of PGRs to recommend a specific regulator for each task and briefly analyze the physiological basis for each.
Summarize the key differences between arithmetic and geometric growth in plants. Include the mathematical expression for each type.
Design a controlled experiment to conclusively prove that the tip of the coleoptile is the source of a transmittable substance responsible for phototropism. Your design must include a control group and at least two experimental groups.