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.

Fungi are saprotrophs, meaning they obtain nutrients by decomposing dead and decaying organic matter, playing a crucial role in nutrient cycling.

The leaves are modified into some other shape or colour of such plants so that insects get attracted and come near it and they are trapped.

The answer is starch as it is the primary food material produced by Photosynthesis.

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.

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.

Function of Chlorophyll in Photosynthesis:

1. Capturing Solar Energy:
Chlorophyll is a green pigment found in the chloroplasts of plant cells. Its primary function in photosynthesis is to capture solar energy from sunlight. This process is called the light-dependent reaction, where chlorophyll absorbs light energy and converts it into chemical energy.

2. Absorption of Light:
Chlorophyll molecules contain a porphyrin ring structure that enables them to absorb light of specific wavelengths, mainly blue and red light. This absorbed light energy is used to power the photosynthetic process and convert carbon dioxide and water into glucose and oxygen.

3. Energy Transfer:
Once chlorophyll captures light energy, it transfers this energy to other molecules in the chloroplast, such as the reaction center of photosystem I and II. These molecules further use this energy to drive the synthesis of ATP and NADPH, which are essential for the Calvin cycle, the second phase of photosynthesis.

4. Essential for Photosynthesis:
Without chlorophyll, plants would not be able to capture sunlight and convert it into chemical energy. This pigment plays a crucial role in the overall process of photosynthesis, allowing plants to produce their own food and release oxygen as a byproduct.
In conclusion, chlorophyll's primary function in photosynthesis is to capture solar energy, which is essential for driving the chemical reactions that enable plants to convert carbon dioxide and water into glucose and oxygen.

Structure in Leaves for Gas Exchange
Gas exchange in leaves primarily occurs through specialized structures called stomata. Stomata are tiny pores found on the surface of leaves, mainly in the lower epidermis. These pores are surrounded by two specialized cells known as guard cells.

Function of Stomata
1. Regulation of Gas Exchange: Stomata regulate the exchange of gases such as oxygen and carbon dioxide between the plant and the environment. During photosynthesis, carbon dioxide enters the leaf through stomata, while oxygen produced as a byproduct exits through the same pores.
2. Water Regulation: Stomata also play a crucial role in regulating water loss from the plant through a process called transpiration. The opening and closing of stomata by the guard cells help in controlling the loss of water vapor.
3. Temperature Regulation: Stomata can also regulate the temperature of the leaf by adjusting the rate of transpiration. This helps in preventing overheating of the leaf tissue.

Importance of Stomata
1. Photosynthesis: Stomata facilitate the entry of carbon dioxide, which is essential for the process of photosynthesis. This allows plants to produce glucose and oxygen for their metabolic processes.
2. Respiration: Stomata enable the exit of oxygen, a byproduct of photosynthesis, from the leaf. Oxygen is required for respiration in plant cells.
3. Environmental Adaptation: The number and distribution of stomata on leaves can vary depending on environmental conditions such as light intensity, humidity, and temperature. This adaptation helps plants survive in different habitats.
In conclusion, stomata are crucial structures in leaves that enable the exchange of gases necessary for plant growth and survival. Their specialized function allows plants to maintain proper gas balance, regulate water loss, and respond to environmental changes effectively.

Symbiotic Relationship between Fungi and Algae in Lichens
Fungi and algae have a symbiotic relationship in lichens, where they live together in a mutually beneficial partnership. This relationship is essential for the survival and growth of lichens.

Mutualism
The relationship between fungi and algae in lichens is a form of mutualism, where both organisms benefit from each other. The fungi provide a protective structure for the algae to grow within, while the algae provide essential nutrients through photosynthesis. This mutual exchange of resources allows both organisms to thrive in various habitats.

Structure of Lichens
Lichens are made up of a fungal partner (mycobiont) and an algal partner (photobiont) living together in a symbiotic association. The fungal partner provides a protective environment and absorbs water and nutrients from the surrounding environment. The algal partner, on the other hand, produces food through photosynthesis using sunlight.

Benefits of Symbiosis
The symbiotic relationship between fungi and algae in lichens allows them to colonize harsh environments where neither organism could survive alone. Lichens can grow on rocks, trees, and even in extreme climates like deserts and tundras. This partnership enhances the adaptability and resilience of lichens in diverse ecosystems.

Conclusion
In conclusion, the relationship between fungi and algae in lichens is a prime example of symbiosis in nature. This partnership allows both organisms to thrive in challenging environments by working together and benefiting from each other's strengths.

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.

Photosynthesis requires carbon dioxide, water, and sunlight to produce carbohydrates and oxygen. Oxygen is a byproduct, not a raw material.

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.

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.

Replenishing Nutrients:
Fertilisers and manures are essential for maintaining soil health because they replenish nutrients that are depleted by plants. As plants grow and take up nutrients from the soil, the soil becomes deficient in essential elements like nitrogen, phosphorus, and potassium. Fertilisers and manures provide these nutrients back to the soil, ensuring that plants have access to the necessary elements for their growth and development.

Improving Soil Structure:
In addition to replenishing nutrients, fertilisers and manures also help improve the soil structure. They enhance soil fertility by promoting the growth of beneficial microorganisms that break down organic matter and release nutrients in a form that plants can absorb. This process helps to create a healthy and fertile soil environment that is conducive to plant growth.

Enhancing Water Retention:
Fertilisers and manures can also help improve the water retention capacity of the soil. By adding organic matter to the soil, they increase its ability to hold onto water and prevent runoff. This is especially important in areas with limited water availability, as it helps plants access moisture more efficiently and reduces the need for frequent irrigation.

Promoting Plant Growth:
Ultimately, the use of fertilisers and manures leads to healthier and more productive plants. By providing essential nutrients, improving soil structure, and enhancing water retention, they create an optimal environment for plant growth. This results in higher yields, better quality produce, and overall improved soil health.
In conclusion, fertilisers and manures play a crucial role in maintaining soil health by replenishing nutrients, improving soil structure, enhancing water retention, and promoting plant growth. Their use is essential for sustainable agriculture practices and ensuring the long-term productivity of the land.

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

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.

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.

Effect of Decreased Light Intensity on Photosynthesis:
When the intensity of light decreases, the rate of photosynthesis is affected in the following way:
- Photosynthesis Rate Decreases:
- Photosynthesis is a process that requires light energy to convert carbon dioxide and water into glucose and oxygen. A decrease in the intensity of light means there is less light energy available for the process of photosynthesis. As a result, the rate of photosynthesis decreases.
- Reduction in ATP and NADPH Production:
- Light is essential for the production of ATP and NADPH, which are crucial for the light-dependent reactions of photosynthesis. With reduced light intensity, the production of these energy carriers decreases, leading to a slowdown in the overall photosynthetic process.
- Impact on Carbon Fixation:
- Reduced light intensity affects the Calvin cycle, which is responsible for carbon fixation. This process involves the conversion of carbon dioxide into glucose. When light is limited, the rate of carbon fixation decreases, ultimately affecting the overall productivity of the plant.
- Stomatal Closure:
- In response to low light intensity, plants may close their stomata to prevent water loss. However, this closure also reduces the availability of carbon dioxide for photosynthesis, further impacting the rate of the process.
In conclusion, a decrease in the intensity of light negatively impacts the rate of photosynthesis by limiting the availability of light energy and affecting key processes involved in the conversion of carbon dioxide into glucose.

Adding Fertilizers to Soil
Adding fertilizers to soil serves the primary purpose of providing essential nutrients to plants for their optimal growth and development. This practice is vital for maintaining soil fertility and ensuring healthy plant growth.

Key Points:
- Nutrient Supply: Fertilizers contain essential nutrients like nitrogen, phosphorus, and potassium which are crucial for plant growth. These nutrients may be deficient in the soil naturally or depleted over time due to continuous cultivation. Adding fertilizers helps replenish these nutrients, promoting healthy plant growth.
- Improving Soil Fertility: Fertilizers not only provide nutrients to plants but also contribute to improving overall soil fertility. Nutrient-rich soil supports a diverse range of plant life and enhances the overall health of the ecosystem.
- Enhancing Crop Yield: By supplying plants with the necessary nutrients, fertilizers help increase crop yield and improve the quality of the produce. This is especially important in agricultural practices where high productivity is essential.
- Promoting Plant Health: Adequate nutrient supply from fertilizers ensures that plants are healthy and resistant to diseases and pests. Strong, healthy plants are better equipped to withstand environmental stressors and produce higher yields.
In conclusion, the primary purpose of adding fertilizers to soil is to supply essential nutrients to plants, improve soil fertility, enhance crop yield, and promote overall plant health. This practice is essential for sustainable agriculture and ensuring food security for the growing global population.

**Conversion of Nitrogen in Soil**
Nitrogen, an essential nutrient for plant growth, exists in the soil in various forms, but plants can only uptake it in a specific form. To make nitrogen usable for plants, it needs to be converted into a soluble form that plants can absorb.
**Role of Bacteria**
- Bacteria play a crucial role in this process by converting atmospheric nitrogen (N2) into a form that plants can use, a process known as nitrogen fixation.
- Some soil bacteria, like Rhizobium species, are capable of converting atmospheric nitrogen into ammonia (NH3) through a process called biological nitrogen fixation.
- Other soil bacteria, like Azotobacter and Azospirillum, can convert atmospheric nitrogen into nitrates (NO3-) through a process called nitrification.
**Conversion into Soluble Form**
- Once nitrogen is fixed by these bacteria, it is converted into a soluble form such as ammonia or nitrates, which can be readily absorbed by plant roots.
- This conversion process makes nitrogen available for plants to use in their growth and development.
In conclusion, nitrogen in the soil is made usable for plants through the action of specific bacteria that convert atmospheric nitrogen into a form that plants can absorb. This process of nitrogen fixation and conversion into a soluble form is essential for ensuring that plants have access to an adequate nitrogen supply for their growth.

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