All questions of Nutrition in Plants for Class 7 Exam

Plants that depend on other plants for food are called parasites. They extract nutrients from their host plant, often harming it in the process.

Chlorophyll's main role in photosynthesis is to capture the solar energy, which is then used to convert carbon dioxide and water into carbohydrates. This process is crucial for the synthesis of food in plants.

Plants that derive nutrients from dead and decaying matter are called saprotrophs. They secrete digestive enzymes onto the decaying material to break it down and absorb the nutrients. Fungi, such as mushrooms and molds, are common examples of saprotrophs. An interesting fact is that saprotrophs play a crucial role in ecosystems by recycling nutrients back into the soil, supporting plant growth.

Stomata are tiny pores located on the surface of leaves that allow the exchange of gases, including the intake of carbon dioxide and release of oxygen during photosynthesis. Each stoma is surrounded by guard cells that regulate its opening and closing. An interesting fact is that the number of stomata can vary greatly between different plant species and environmental conditions, helping plants adapt to their surroundings.

In lichens, fungi and algae live in a symbiotic relationship where the fungi provide shelter and minerals, while the algae perform photosynthesis and provide food.

Introduction:
Carnivorous plants are a unique group of plants that have evolved to obtain nutrients by trapping and digesting small animals, mainly insects. They have developed specialized structures to capture their prey. Among these structures, the leaves are primarily responsible for trapping insects.

Leaves as Trapping Mechanism:
The leaves of carnivorous plants have adapted to form various trapping mechanisms that enable them to capture and digest insects. These trapping mechanisms can be broadly classified into two main types: active and passive traps.

Active Traps:
1. Snap traps: Plants like the Venus flytrap possess specialized leaves that have sensitive trigger hairs. When an insect touches these hairs, the leaves rapidly close, trapping the prey.
2. Bladder traps: Bladderworts have small bladder-like structures on their leaves that create a vacuum when triggered by prey. This vacuum pulls the insect inside, where it is digested.

Passive Traps:
1. Pitfall traps: Pitcher plants have leaves that form deep, pitcher-shaped structures filled with digestive enzymes. Insects are lured by nectar and fall into these pitchers, unable to escape.
2. Sticky traps: Sundews and butterworts have leaves covered in sticky glandular hairs. When an insect lands on these leaves, it gets stuck, and the plant slowly digests it.

Other Parts of Carnivorous Plants:
While the leaves are the primary trapping mechanism in carnivorous plants, other parts of these plants have different functions:
- Roots: The roots of carnivorous plants primarily serve to anchor the plant in the soil and absorb water and minerals.
- Flowers: The flowers of carnivorous plants are responsible for reproduction, attracting pollinators such as insects or birds.
- Stems: The stems of carnivorous plants provide structural support and help transport water and nutrients throughout the plant.

Conclusion:
In conclusion, the leaves of carnivorous plants are the main structures responsible for trapping insects. They have evolved various mechanisms, such as snap traps, bladder traps, pitfall traps, and sticky traps, to capture and digest prey. While other parts of the plant, such as roots, flowers, and stems, have different functions, it is the specialized leaves that make carnivorous plants unique and fascinating.

The primary mode of nutrition for plants is autotrophic nutrition, where they synthesize their own food using sunlight, carbon dioxide, and water. This process, known as photosynthesis, occurs mainly in the leaves of plants due to the presence of chlorophyll. An interesting fact is that photosynthesis not only produces food but also releases oxygen, which is essential for the survival of most living organisms on Earth.

Iodine solution is used to test for the presence of starch. When applied to a leaf, it turns blue-black if starch is present, indicating that photosynthesis has occurred.

Chlorophyll is the green pigment in the leaves responsible for capturing sunlight, which is crucial for photosynthesis. Chlorophyll absorbs light most efficiently in the blue and red wavelengths, while reflecting green light, which is why plants appear green. An additional interesting fact is that chlorophyll is structurally similar to hemoglobin in blood, but instead of iron, it has magnesium at its core.

Fertilisers and manures replenish nutrients in the soil that are depleted by plant growth, ensuring continued soil fertility and plant health.

The rate of photosynthesis decreases if the light intensity decreases, as light is a crucial factor for the process.

The process of photosynthesis is described in this line because, photosynthesis is the process of making food for a plant and it requires carbon dioxide and water to a plant for this process. Carbon dioxide and water is merged in the leaves of the plant to make glucose, a simple carbohydrate, which is later stored in the leaves of the plant in the form of glucose, a complex carbohydrate. In this whole process, oxygen is released and glucose is formed.

Primary Food Material Produced by Photosynthesis: Starch

Photosynthesis is the process by which green plants, algae, and some bacteria convert light energy from the sun into chemical energy in the form of glucose. This glucose is then used to produce various organic compounds necessary for the growth and development of the plant. The primary food material produced by photosynthesis is starch.

Explanation:

1. Photosynthesis:
Photosynthesis is a vital process for the survival of plants and other photosynthetic organisms. It occurs in the chloroplasts, which are specialized organelles found in plant cells. The process involves the conversion of carbon dioxide and water into glucose and oxygen, using sunlight as the primary source of energy.

2. Glucose:
Glucose is a simple sugar molecule that serves as the main source of energy for plants. It is a primary product of photosynthesis and is used by plants for various metabolic processes. However, glucose alone cannot be stored for a long time due to its solubility in water.

3. Starch:
To store glucose efficiently, plants convert it into starch. Starch is a complex carbohydrate made up of multiple glucose molecules linked together. It is insoluble in water, making it suitable for storage. Plants store starch in various parts like roots, tubers, and seeds, where it can be broken down into glucose when needed for energy.

Starch serves as a long-term energy reserve for plants. When photosynthesis is actively occurring, excess glucose produced is converted into starch and stored. During periods of limited sunlight or when energy demands are high, plants can break down starch to release glucose for energy production.

4. Other Organic Compounds:
Although starch is the primary food material produced by photosynthesis, plants also produce other organic compounds essential for growth and development. These include proteins, lipids (fats), and minerals. However, these compounds are not directly produced by photosynthesis but are synthesized using the glucose and energy generated during the process.

Proteins are made up of amino acids and are crucial for various cellular functions. Lipids, such as fats and oils, are important for energy storage, insulation, and structural components of cells. Minerals, on the other hand, are inorganic substances required in small amounts for the proper functioning of plants.

Conclusion:
In conclusion, the primary food material produced by photosynthesis is starch. Starch is a complex carbohydrate synthesized from glucose and serves as a long-term energy reserve for plants. While other organic compounds like proteins, fats, and minerals are also synthesized using glucose, starch is the primary storage form of energy produced by photosynthesis.

Fertilizers are added to soil to provide essential nutrients like nitrogen, potassium, and phosphorus, which help in plant growth and soil fertility.

Main Function of Guard Cells:
Guard cells play a crucial role in the functioning of leaves by regulating the opening and closing of stomata. Stomata are tiny pores present on the surface of leaves that allow for the exchange of gases such as oxygen, carbon dioxide, and water vapor.

Regulating Stomatal Opening and Closing:
1. Opening: When guard cells are turgid (swollen with water), they bow outwards, creating an opening between them known as the stomatal pore. This allows for the influx of carbon dioxide needed for photosynthesis.
2. Closing: Conversely, when guard cells lose water and become flaccid, they close up, restricting the entry of carbon dioxide and reducing water loss through transpiration. This mechanism helps plants conserve water during dry conditions.

Importance of Stomatal Regulation:
1. Photosynthesis: By controlling stomatal opening, guard cells ensure an adequate supply of carbon dioxide for photosynthesis, the process by which plants produce food using sunlight.
2. Water Conservation: Guard cells help prevent excessive water loss by adjusting stomatal opening based on environmental conditions. This is especially important for plants growing in arid regions or during drought periods.
3. Temperature Regulation: Stomatal regulation also plays a role in temperature control. When stomata are open, water vapor is released through transpiration, cooling the leaf surface. Closing stomata reduces water loss and helps maintain optimal leaf temperature.

In conclusion, guard cells are essential for maintaining the balance between gas exchange and water conservation in plants. Their ability to regulate stomatal opening and closing ensures efficient photosynthesis, optimal water usage, and temperature regulation, contributing to the overall health and survival of plants.

Nitrogen in the soil is converted into a usable, soluble form by bacteria, such as Rhizobium, which helps plants utilize nitrogen for growth.

Reducing water loss through modified leaves into spines
Desert plants often have leaves that are modified into spines as a way to adapt to their arid environment. This modification serves the primary purpose of reducing water loss, which is crucial for survival in a habitat where water is scarce.

Protection against water loss
The spines on desert plants help to reduce water loss by minimizing the surface area exposed to the hot and dry conditions of the desert. By having fewer and smaller leaves, the plant can conserve water and reduce the risk of dehydration.

Preventing herbivory
Additionally, the spines on desert plants serve as a form of defense against herbivores. The sharp and often tough spines act as a deterrent to animals that may try to feed on the plant, helping to protect the plant's limited resources.

Adaptation to harsh environment
In the harsh environment of the desert, where water is scarce and conditions are extreme, plants have evolved various adaptations to survive. The modification of leaves into spines is one such adaptation that helps desert plants thrive in their challenging environment.
In conclusion, the modification of leaves into spines in desert plants primarily serves the purpose of reducing water loss, enabling the plant to conserve water and survive in the arid conditions of the desert.

Understanding Symbiosis
Symbiosis refers to a close and often long-term interaction between two different biological species. The interactions can be mutualistic, commensal, or parasitic. The characteristic feature of symbiosis is best captured in option C.
Key Characteristics of Symbiosis:
- Mutual Benefit: In mutualistic relationships, both organisms benefit from the interaction. For example, bees and flowering plants exemplify this, as bees obtain nectar while aiding in pollination.
- Close Association: The organisms involved typically live in close proximity to each other, which facilitates the interaction and exchange of benefits.
- Diverse Relationships: Symbiosis can manifest in various forms:
- Mutualism: Both species benefit.
- Commensalism: One species benefits while the other is neither helped nor harmed.
- Parasitism: One organism benefits at the expense of the other (not true symbiosis in the mutualistic sense).
Why Other Options Are Incorrect:
- Option A: "Organism feeds on dead and decaying organic matter" describes saprophytism, not symbiosis.
- Option B: "Organism traps and feeds on insects" refers to carnivorous plants, which do not necessarily involve a symbiotic relationship.
- Option D: "One organism grows as a parasite on the body of another" describes parasitism specifically, which is not mutualistic as it harms the host.
Conclusion:
Thus, the defining feature of symbiosis is that two organisms live together and benefit from the relationship, making option C the correct answer. This concept is essential in understanding ecological interactions and the balance of ecosystems.

Saprotrophs, such as fungi, absorb nutrients from dead and decaying matter, while parasites depend on living hosts for their nutrition.

Leaves are known as the food factory of plants because they contain chlorophyll and are the primary site of photosynthesis where food is synthesized.

Nitrogen-fixing bacteria are crucial for plants because they convert atmospheric nitrogen into a form that plants can absorb and use. These bacteria, often found in the roots of legumes, provide plants with essential nitrogen that is needed for protein synthesis and overall growth, thus reducing the need for synthetic nitrogen fertilizers.