Introduction to Plant Physiology

Plant physiology is the branch of biology that deals with the study of vital life processes occurring in plants. It explains how plants absorb water and minerals, manufacture food, respire, grow, and respond to environmental stimuli. For NEET aspirants, plant physiology is one of the most scoring and concept-based units of Class 11 Biology. A clear understanding of plant physiological processes is essential to answer both theoretical and numerical questions in NEET.

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Absorption of Water and Minerals

Plants absorb water mainly through root hairs by the process of diffusion and osmosis. Minerals are absorbed in ionic form through active and passive transport mechanisms.

Water absorption occurs by:

• Passive absorption – due to transpiration pull

• Active absorption – using metabolic energy

Minerals like nitrogen, phosphorus, potassium, calcium, magnesium, and iron are essential for plant growth. Deficiency of these minerals leads to specific deficiency symptoms such as chlorosis, necrosis, and stunted growth.

Transport of Water and Minerals

The upward movement of water and minerals from roots to aerial parts occurs through xylem tissue. This process is mainly driven by:

• Root pressure

• Capillarity

• Transpiration pull (most important)

The cohesion-tension theory explains the ascent of sap due to continuous water columns and transpiration pull.

Transpiration

Transpiration is the loss of water in the form of water vapour from the aerial parts of the plant, mainly through stomata.

Types of transpiration:

• Stomatal transpiration

• Cuticular transpiration

• Lenticular transpiration

Functions of transpiration include cooling of plants, ascent of sap, and maintenance of water balance. Factors affecting transpiration include light, temperature, humidity, wind, and leaf area.

Photosynthesis

Photosynthesis is the process by which green plants synthesize food using carbon dioxide, water, and sunlight in the presence of chlorophyll.

Overall equation:
6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂

Photosynthesis occurs in two stages:

1. Light Reaction:

• Takes place in thylakoid membranes

• Produces ATP and NADPH

• Releases oxygen

2. Dark Reaction (Calvin Cycle):

• Occurs in stroma

• Fixes CO₂ into glucose

Plants are classified into C₃ plants, C₄ plants, and CAM plants based on their CO₂ fixation pathways. Understanding differences between these is crucial for NEET.

Respiration in Plants

Respiration is the process of breaking down glucose to release energy. It occurs in all living plant cells.

Types of respiration:

• Aerobic respiration – occurs in presence of oxygen

• Anaerobic respiration – occurs in absence of oxygen

Stages of aerobic respiration:

1. Glycolysis

2. Krebs cycle

3. Electron transport chain

Energy released during respiration is stored as ATP, which is used for growth and metabolism.

Plant Growth and Development

Plant growth is an irreversible increase in size, while development includes growth, differentiation, and maturation.

Growth phases:

• Meristematic phase

• Elongation phase

• Maturation phase

Plant growth is regulated by plant hormones (phytohormones).

Plant Growth Regulators (Phytohormones)

Phytohormones are organic substances that regulate plant growth and development.

Major plant hormones include:

• Auxins – cell elongation and apical dominance

• Gibberellins – stem elongation and seed germination

• Cytokinins – cell division and delay of senescence

• Ethylene – fruit ripening

• Abscisic Acid (ABA) – growth inhibitor, stress hormone

Questions based on functions and examples of plant hormones are very common in NEET.

Mineral Nutrition in Plants

Plants require minerals for enzyme activation, structural components, and metabolic activities.

Essential elements are classified into:

• Macronutrients – N, P, K, Ca, Mg, S

• Micronutrients – Fe, Mn, Zn, Cu, Mo, B, Cl

Nitrogen metabolism and nitrogen fixation are important subtopics frequently tested in NEET.

Importance of Plant Physiology for NEET

Plant physiology is a high-weightage unit in NEET Biology because:

• Questions are concept-based and scoring

• Diagrams and processes are repeatedly asked

• Forms the base for ecology and biotechnology

Proper understanding helps students solve assertion-reason and application-based questions easily.

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Conclusion

Plant Physiology explains how plants survive, grow, and reproduce through various physiological processes. Mastery of this chapter is essential for scoring high in NEET Biology. With clear concepts, diagrams, and regular practice, students can easily excel in this unit. StudentBro.in provides structured, exam-oriented NEET Biology notes to help students revise effectively and confidently.