Nutrition in Plants Class 7 Notes Science Chapter 1

Introduction

• Food is essential for all living organisms.
• Carbohydrates, proteins, fats, vitamins, and minerals are components of food.
• These components are known as nutrients and are vital for our bodies.
• All living organisms, including humans, require food.

Nutrients in Plants

• Plants have the ability to produce their own food, while animals, including humans, cannot. They obtain food from plants or other animals that consume plants.
• Therefore, humans and animals are directly or indirectly reliant on plants for their food supply.

Mode of Nutrition in Plants

• Plants are unique organisms capable of producing their food using water, carbon dioxide, and minerals present in their environment.
• Nutrients obtained by plants are essential for building and repairing their bodies, as well as providing energy for life processes.
• Nutrition refers to the process of acquiring and utilizing food by an organism.
• Autotrophic nutrition is when organisms create food from basic substances, hence plants are known as autotrophs.
• Animals and most other organisms are heterotrophs that consume food prepared by plants.

Photosynthesis- Food-Making Process in Plants

• Food production in plants is a crucial aspect. It is important to know if food is synthesized in all plant parts or specific regions.
• Plants acquire raw materials from their surroundings and transport them to their food factories.
• Photosynthesis is the process by which plants produce food, primarily occurring in their leaves.
• Raw materials required for photosynthesis include water and minerals absorbed by roots, and carbon dioxide taken in through leaf pores called stomata.

Stomata

• Transport vessels in plants carry water and minerals to the leaves, forming a continuous path for nutrient delivery.
• Chlorophyll, a green pigment in leaves, captures sunlight energy necessary for synthesizing food from carbon dioxide and water.
• Photosynthesis, reliant on sunlight, chlorophyll, carbon dioxide, and water, is crucial for producing food and oxygen essential for life on Earth.
• In the absence of photosynthesis, food production would cease, impacting the survival of most living organisms and making life on Earth impossible.
• During photosynthesis, chlorophyll-containing leaf cells use sunlight to convert carbon dioxide and water into carbohydrates, releasing oxygen as a byproduct.

Chlorophyll

• The presence of starch in leaves indicates successful photosynthesis, as starch is a form of carbohydrate produced in the process.
• Living organisms' bodies consist of cells, similar to how buildings are constructed of bricks.
• Cells, the fundamental units of life, are visible only under a microscope.
• Some organisms are unicellular, composed of a single cell enclosed by a cell membrane.
• Most cells contain a centralized spherical structure known as the nucleus, surrounded by cytoplasm.

Photosynthesis

Synthesis of plant food components other than carbohydrates

• Plants create carbohydrates via photosynthesis using carbon, hydrogen, and oxygen.
• These carbohydrates are utilized to produce proteins and fats.
• Plants need nitrogen for synthesizing proteins, which are nitrogen-containing compounds.
• Nitrogen, abundant in the air in gaseous form, cannot be directly absorbed by plants.
• Special soil bacteria transform gaseous nitrogen into a usable form and release it into the soil for plant absorption.
• Farmers often apply nitrogen-rich fertilizers to the soil to meet plant nitrogen requirements.
• Once plants obtain nitrogen along with water, they can synthesize proteins and vitamins.

Other Modes of Nutrition in Plants

• Some plants lack chlorophyll and cannot make their own food.
• Plants like Cuscuta (Amarbel) are examples of such plants.
• Cuscuta is a parasite plant that takes food from the plant it climbs on, known as the host.

• There are plants that can trap and digest insects for nutrients, known as insectivorous plants.
• Insectivorous plants have specialized structures like pitchers to trap insects.
• These plants digest the trapped insects and absorb their nutrients.
• Such plants may not obtain all necessary nutrients from the soil they grow in.

Saprotrophs

• Saprotrophs are organisms like fungi that obtain nutrients from dead and decaying matter through saprotrophic nutrition.
• Fungi, such as mushrooms, absorb nutrients from their surroundings, including bread, pickles, leather, and clothes left in hot and humid conditions.

Saprotrophs

• Fungal spores, commonly present in the air, germinate on wet and warm surfaces, leading to growth and potential spoilage of items.
• Protection from fungal spoilage involves keeping items dry and cool to prevent spore germination.
• Symbiosis involves a mutually beneficial relationship between organisms, such as certain fungi living in plant roots and lichens composed of algae and fungi working together.
• In plant-fungus symbiosis, plants provide nutrients to fungi, while fungi offer water and specific nutrients in return.
• Lichens consist of a partnership between chlorophyll-containing algae and fungi where the algae produce food through photosynthesis, benefiting both partners.

How Nutrients are Replenished in the Soil

• Farmers spread manure or fertilisers in fields to replenish nutrients in the soil.
• Plants absorb minerals and nutrients from the soil, leading to a decline in soil nutrients over time.
• Fertilisers and manures contain essential nutrients like nitrogen, potassium, and phosphorous which need to be added periodically to enrich the soil.
• Crop plants, especially, absorb a significant amount of nitrogen, causing nitrogen deficiency in the soil.
• Plants require nitrogen in a soluble form, which is not readily available from the air.
• The bacterium Rhizobium converts atmospheric nitrogen into a usable form for plants, particularly legumes like gram, peas, and beans.
• Rhizobium forms a symbiotic relationship with these plants, exchanging nitrogen for food and shelter.

Rhizobium Nodules

• The association between Rhizobium and leguminous plants reduces the need for nitrogenous fertilisers, benefiting farmers.
• Most plants are autotrophs, while some are parasitic or saprotrophic, deriving nutrition from other organisms.
• Insectivorous plants can be considered partial heterotrophs, as they supplement their nutrition by consuming insects.