Biology Chapter 9: Plant Nutrition

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Questions and Answers

Explain the relationship between light intensity and the rate of photosynthesis and respiration in plants.

As light intensity increases, the rate of photosynthesis increases, while the rate of respiration remains largely constant. At low light intensities, respiration dominates, leading to a net uptake of oxygen and release of carbon dioxide. As light intensity increases, photosynthesis eventually surpasses respiration, resulting in a net uptake of carbon dioxide and release of oxygen. At the compensation point, the rates of photosynthesis and respiration are equal, and there is no net gas exchange.

Describe the net gas exchange in plants during the night and explain why this occurs.

During the night, plants exhibit a net uptake of oxygen and release of carbon dioxide. This is because photosynthesis ceases in the absence of light, while respiration continues, leading to the consumption of oxygen and production of carbon dioxide.

What is the compensation point in photosynthesis, and why is it significant for plant survival?

The compensation point is the light intensity at which the rate of photosynthesis equals the rate of respiration. This point is significant because it represents the minimum light intensity needed for a plant to maintain a stable supply of energy through photosynthesis and respiration.

Explain how factors such as carbon dioxide concentration and temperature can limit the rate of photosynthesis.

Factors such as carbon dioxide concentration and temperature, even when light intensity is high, can limit the rate of photosynthesis. Increasing carbon dioxide concentration can boost photosynthesis, but beyond an optimal level, further increases have little effect. Similarly, while increasing temperature can initially enhance photosynthetic rates, exceeding an optimal point may lead to a decline in activity due to enzyme denaturation. Signup and view all the answers

Describe the primary sites of gas exchange in plants, and briefly explain their role in this vital process.

Plants rely on various structures for gas exchange. Lenticels, small pores in the bark, facilitate gas exchange between the interior of stems and the atmosphere. Roots also participate in gas exchange, absorbing oxygen for respiration and releasing carbon dioxide. The leaves, with their numerous stomata, are the primary sites of gas exchange during photosynthesis and respiration. Signup and view all the answers

Explain how the structure of leaves aids in their primary function of gas exchange.

Leaves are broad and flat to maximize surface area for gas exchange. They are also thin, reducing the diffusion distance for gases. The mesophyll cells have moist surfaces for gas dissolution, and there are air spaces within the spongy mesophyll for efficient gas diffusion. Stomata on the epidermis allow for gas entry and exit, and guard cells regulate the rate of gas exchange. Signup and view all the answers

Describe the process of gas release from leaves, explaining how these gases reach the atmosphere.

Gases produced within the cells diffuse into neighboring cells and eventually reach the air spaces near the stomata. These gases then dissolve in the moist surfaces of the mesophyll cells and diffuse into the air spaces. Finally, gases from the air spaces diffuse out through the stomata into the atmosphere. Signup and view all the answers

What is the significance of air spaces within the spongy mesophyll in facilitating gas exchange?

Air spaces within the spongy mesophyll allow gases to diffuse freely within the leaf, facilitating efficient gas exchange between cells and the atmosphere. These spaces reduce the diffusion distance for gases, making the exchange process faster and more efficient. Signup and view all the answers

How do the adaptive features of leaves contribute to their overall efficiency in gas exchange?

The adaptive features of leaves, including their broad and flat shape, thin structure, moist cell surfaces, air spaces, stomata, and controlled stomatal opening, collectively contribute to efficient gas exchange. These features create favorable conditions for gas diffusion, solubility, and regulation, maximizing the uptake of carbon dioxide for photosynthesis and the release of oxygen for respiration. Signup and view all the answers

Explain why a deficiency of magnesium would lead to poor growth and yellow leaves in plants.

Magnesium is a key component of chlorophyll, the pigment responsible for absorbing light energy during photosynthesis. A lack of magnesium restricts chlorophyll production, resulting in reduced photosynthetic activity and therefore a decline in plant growth. This is manifested by yellowing leaves as the plant loses its green pigment. Signup and view all the answers

Describe the role of the aluminium foil in the experimental setup for testing the effects of minerals on plant growth. Why is it necessary to exclude light from the setup?

The aluminium foil serves to block light and prevents algae from carrying out photosynthesis. This is crucial because algae would compete with the seedlings for the minerals in the solution and potentially clog the root hairs, interfering with the experiment's focus on the effects of specific minerals on plant growth. Signup and view all the answers

What is the purpose of the cotton wool in the experimental setup for testing the effects of minerals on plant growth?

The cotton wool acts as a barrier, preventing contamination by bacteria or fungi that could enter the solution and potentially disrupt the plant's growth or introduce additional variables, interfering with the study of the mineral's effects. Signup and view all the answers

Why are young seedlings preferred over mature plants in this experiment?

Young seedlings are preferred because their rapid growth rate allows for more prominent and readily observable results. Changes in their growth patterns due to mineral deficiencies or variations in nutrient solutions will be more noticeable and easier to quantify in a shorter time frame. Signup and view all the answers

Explain the purpose of bubbling air into the nutrient solution in the experimental setup. Why is it important to provide oxygen, but not carbon dioxide, to the roots?

The air bubbled into the solution provides oxygen for root respiration. Roots, like all living cells, require oxygen for respiration, which releases energy for their growth and function. Supplying carbon dioxide would not be beneficial as it is used during photosynthesis, a process that takes place in the leaves, not the roots. Signup and view all the answers

Explain why there is a need for renewal of the nutrient solution in the experimental setup?

The nutrient solution needs to be renewed because the plants gradually absorb minerals from it over time. As the nutrients are depleted, the solution becomes less effective in supporting growth, and the plants may suffer deficiencies if the solution is not replaced. Signup and view all the answers

Describe the structure and function of the palisade mesophyll in a leaf. How is its structure related to its function in photosynthesis?

The palisade mesophyll is the layer of tightly packed, cylindrical cells located below the upper epidermis. These cells possess numerous chloroplasts, which are the sites of photosynthesis. The compact arrangement and high chloroplast content maximize the light absorption and energy conversion for photosynthesis, promoting efficient energy production for the plant. Signup and view all the answers

Why is the cuticle important for the survival of a plant?

The cuticle, a waxy layer covering the epidermis of both the upper and lower leaf surfaces, acts as a protective barrier that minimizes water loss through transpiration. This is crucial for plant survival, especially in dry environments, as it helps maintain the plant's water balance and prevents dehydration. Signup and view all the answers

What process do plants use to convert carbon dioxide and water into carbohydrates?

Photosynthesis Signup and view all the answers

Which element is essential for the synthesis of proteins in plants and how is it absorbed?

Nitrogen, absorbed as nitrate or ammonium ions. Signup and view all the answers

What role does phosphorus play in plant nutrition?

It is required for the synthesis of nucleic acids and some enzymatic reactions. Signup and view all the answers

Identify one major mineral element and its associated deficiency symptoms in plants.

Potassium; deficiency causes poor growth and curled-up leaves with dark edges. Signup and view all the answers

How do plants obtain the water necessary for photosynthesis?

By absorbing it from the soil. Signup and view all the answers

What distinguishes autotrophic nutrition in plants?

Plants synthesize organic substances from inorganic substances. Signup and view all the answers

What are trace elements, and why are they important for plants?

Trace elements are minerals needed in small amounts for plant growth. Signup and view all the answers

Describe the consequence of nitrogen deficiency in plants.

It leads to poor growth and yellow leaves. Signup and view all the answers

Gas exchange in plants takes place in ______, which are small broken parts of the cork.

lenticels Signup and view all the answers

At the start of the day, light intensity increases, but the rate of ______ is still lower than that of respiration.

photosynthesis Signup and view all the answers

The ______ point occurs when the rate of photosynthesis equals the rate of respiration, resulting in no net gas exchange.

compensation Signup and view all the answers

As light intensity further increases, the rate of photosynthesis does not increase as it is limited by other factors such as ______ concentration and temperature.

carbon dioxide Signup and view all the answers

Gas exchange takes place all over the ______ of plants.

roots Signup and view all the answers

Magnesium is absorbed by plants in the form of ______ ions.

magnesium Signup and view all the answers

Magnesium is a component of ______, a crucial molecule for photosynthesis.

chlorophyll Signup and view all the answers

A deficiency of magnesium can lead to ______ growth and yellow leaves in plants.

poor Signup and view all the answers

The jar in the experimental setup is covered with ______ foil to prevent algae growth.

aluminum Signup and view all the answers

The ______ wool in the experimental setup prevents the entry of bacteria and fungi.

cotton Signup and view all the answers

Air is bubbled into the nutrient solution to supply ______ for respiration by the roots.

oxygen Signup and view all the answers

The ______ mesophyll is made of tightly-packed cylindrical cells with many chloroplasts.

palisade Signup and view all the answers

The ______ is a thin, waxy layer on the surface of leaves that reduces water loss.

cuticle Signup and view all the answers

Plants can make their own food, in form of carbohydrates from carbon dioxide and water using light energy trapped by ______.

chlorophyll Signup and view all the answers

Oxygen is released as a by-product during the process of ______.

photosynthesis Signup and view all the answers

Plants require a variety of minerals, absorbed in forms of ______ for growth.

ions Signup and view all the answers

Nitrogen is absorbed in forms of ______ ions and ammonium ions.

nitrate Signup and view all the answers

Phosphorus is required in the synthesis of ______, which consist of nucleotides.

nucleic acids Signup and view all the answers

Potassium promotes transport and ______ in plants.

photosynthesis Signup and view all the answers

Deficiency of nitrogen leads to poor growth and ______ leaves.

yellow Signup and view all the answers

Trace elements are elements needed in ______ amounts.

trace Signup and view all the answers

Each stoma is guarded by two ______ cells which control the opening and closing of the stoma.

guard Signup and view all the answers

The vascular bundle consists of the ______ and phloem.

xylem Signup and view all the answers

Gases in the air space ______ in the moist surface of the mesophyll cells and diffuses directly into the cells.

dissolve Signup and view all the answers

The surface of the mesophyll cells are ______, allowing the gases to dissolve in it and diffuse directly into the cell.

moist Signup and view all the answers

Stomata are present on the ______, allowing gases to diffuse in and out of the cell easily.

epidermis Signup and view all the answers

Guard cells control the ______ and closing of the stoma, such that the rate of gas exchange can be regulated.

opening Signup and view all the answers

Herbaceous stems have ______ for gas exchange.

stomata Signup and view all the answers

Woody stems are covered by a layer of ______, which is impermeable to air.

cork Signup and view all the answers

Flashcards

What are plants called in terms of their food source?

Plants can create their own food in the form of carbohydrates using sunlight, carbon dioxide, and water. This process is called photosynthesis.

What is the process called that allows plants to make their own food?

Photosynthesis is the process by which plants convert light energy into chemical energy in the form of carbohydrates. This process requires carbon dioxide, water, and chlorophyll to produce glucose and oxygen.

How do plants obtain the necessary water and minerals?

Plants absorb water and minerals from the soil through their roots.

Why are plants called autotrophs?

Autotrophs are organisms that can produce their own food from inorganic substances, like carbon dioxide and water. Plants are examples of autotrophs.