Table of contents | |
Nutrition in Plants | |
Respiration in Plants | |
Transportation in Plants | |
Excretion in Plants | |
Mineral Nutrition in Plants | |
Plant Growth and Development |
Plants undergo various physio-chemical processes such as photosynthesis, cellular respiration, and transpiration, which contribute to their growth, development, and reproduction, thereby completing their life cycle.
Plant nutrition involves the study of essential chemical elements necessary for plant growth.
There are generally two types of nutrition in plants as mentioned below :
Photosynthetic Pigments: Green plants can perform photosynthesis due to the presence of chlorophyll-a and b, along with other accessory pigments. These pigments convert light energy into chemical energy stored in organic compounds (carbohydrates).
The food produced during photosynthesis is broken down in the mitochondria to release energy through cellular respiration.
Basic reaction of cellular respiration is as under
This energy is used by the plant to synthesize other necessary molecules.
The cell respiration is of following two types
ATP (Adenosine Triphosphate): ATP serves as the energy currency of the cell. The hydrolysis of one ATP molecule releases about 7.6 kcal (31.8 kJ) of energy, which is used by plant cells for various functions.
Leaves are responsible for food production, while roots absorb water. The plant transport system, consisting of xylem and phloem, moves these substances throughout the plant. Xylem transports water and minerals from roots to leaves, and phloem distributes food to roots and other parts of the plant.
Plants excrete various waste products through different processes. Gaseous wastes (O2 and CO2) are expelled through stomata and lenticels, liquid wastes (excess water) through transpiration, and solid wastes (old leaves). Some excreted products, like essential oils, gums, and natural rubber, are useful to humans.
Transpiration is the loss of water vapor from plants, mainly through the stomata in leaves, with some water loss occurring through the general plant surface. Plants have developed adaptations to minimize excessive transpiration, particularly xerophytes in desert areas, which have features like thick waxy cuticles, modified leaves (thorns), or no leaves to reduce the rate of water loss.
Plants absorb minerals as ions from the soil and incorporate them into vital biomolecules.
Essential Elements: Some elements are absolutely necessary for the normal growth, development, and reproduction of plants and are irreplaceable. These elements are directly involved in the plant's metabolism, and without them, plants cannot complete their life cycle or produce seeds. These are known as essential elements, which are categorized into two groups:
Following table gives a brief information about above mentioned nutrients
Nitrogen Metabolism: Nitrogen is a crucial macronutrient as it is a major component of proteins and nucleic acids. Biological nitrogen fixation, a key process in nitrogen metabolism, occurs in the roots of leguminous plants through a symbiotic relationship with Rhizobium bacteria. The steps involved in this process are:
Note: The burning of coal and other fossil fuels releases fixed nitrogen into the atmosphere as nitrogen-based trace gases like nitric oxide, which are then returned to the soil through the nitrogen cycle.
A new plant is formed by the germination of seed. This process is called seed germination. Until the seed start germinating it is kept in dormant stage. Seed germination can be easily understood by following diagram
Growth is regarded as the irreversible permanent increase in the size and biomass of the plant. Plant hormones influence the growth and development of the plant.
Following table gives a brief idea of action of different plant hormones and their location.
The flowering of plants depends on their exposure to light, which is classified into the following categories:
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