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Meat‐eating plants! Meat‐eating plants! Carnivorous plants chomp down on insects in unusual ways. The pitcher plant is among the largest of all pitchers (Nepenthes attenboroughii), and is so big that it can catch rats as well as insects in its leafy trap. Insects, attracted by the secretion, stick to the tips of the longer tentacles, which bend over bringing them inward towards and forming a tight grip. Enzymes secreted by the tentacles digest the insect and the products are absorbed by the leaf. Here, you will learn more about nutritional requirements and examine some nutritional adaptations that have evolved in plants.

Learning Objectives

After completing the topic, the student will be able to:

  • Define and discuss ″plant nutrition″ and explore how plants uptake nutrients.
  • Identify different modes of plant nutrition.
  • Differentiate between micronutrients and macronutrients in terms of amounts required by plants and appreciate their physiological importance.
  • Identify the different types of plant diseases caused due to essential element deficiencies.
  • Explore how plants make most of their nutrients by themselves.
  • Identify different nutritional modes of adaptations seen in plants.
  • Describe the symbiosis between rhizobium bacteria and legume plants and systematize the steps involved in root nodule formation.
  • Analyze how a legume species recognizes a certain strain of Rhizobium among many bacterial strains in the soil.
Plant nutrient uptake Plant nutrient uptake Plants uptake essential elements from the soil through their roots and from the air (mainly consisting of nitrogen and oxygen) through their leaves.
Plant Nutrition

Plant nutrition is the study of the chemical elements that is necessary for plant growth. Nutrition can be defined as the process by which an organism obtains food, which is used to provide energy and materials for its life sustaining activities.

Plants use inorganic minerals for nutrition, whether grown in the field or in a container in solutions of fertilizer minerals in the absence of soil. A good soil supplies the plants with the mineral elements they use.

Nutrient uptake in the soil is achieved by cation exchange, wherein root hairs pump hydrogen ions (H+) into the soil through proton pumps. These hydrogen ions displace cations attached to negatively charged soil particles so that the cations are available for uptake by the root. In the leaves, stomata open to take in carbon dioxide and expel oxygen. The carbon dioxide molecules are used as the carbon source in photosynthesis.

Complex interactions involving weathering of rock minerals, decaying organic matter, animals, and microbes take place to form inorganic minerals in soil. Roots absorb mineral nutrients as ions in soil water.

For example, plants acquire nitrogen in the form of nitrate ions (NO3−). Many factors influence nutrient uptake for plants. Ions can be readily available to roots or could be "tied up" by other elements or the soil itself. Soil too high in pH (alkaline) or too low (acid) makes minerals unavailable to plants.

Mineral Composition Mineral composition is important for healthy plant growth The mineral nutrients, which come from the soil, are dissolved in water and absorbed through plant's roots. There are not always enough of these nutrients in the soil for a plant to grow healthy. That is why many farmers and gardeners use fertilizers to add the nutrients to the soil.
Mineral composition for healthy plant growth

The precise mineral composition of plants is of great importance, in the sense, particularly when a plant is considered as a food source. Plant's composition indicates the fertility of soil in which it is grown. We can restore the fertility of soil through fertilizers by observing the deficiency symptoms of any element in plants.

The essential elements most commonly used and added to the soil in the form of fertilizer are nitrogen, phosphorus and potassium. These are the major nutrients.

Food contains various organic and inorganic substances. Those, which are required by the organisms to carry out life functions are called nutrients. Nutrients are of various types ‐ carbohydrates, fats, proteins, vitamins and minerals.
The various nutrients carry out different functions such as:

  • energy production,
  • synthesis of materials for growth and repair of the tissues,
  • synthesis of materials necessary for carrying out and maintaining life functions,
  • synthesis of materials for immune system.

Thus the term nutrition includes the means by which an organism obtains its food and also the processes by which the nutrients in the food are broken down to simpler molecules for utilisation by the body.