Overview of Plant Growth and Mineral Nutrition

1. Plant Growth
   Growth is a characteristic feature of living organisms and is defined as a permanent and irreversible increase in size, mass, or number of cells.
2. Aspects of Growth
   Growth has two aspects: quantitative (increase in size, length, volume, dry weight, and cell number) and qualitative (development and differentiation).
3. Growth and Development
   Development is an ordered and progressive change leading to higher complexity, while differentiation leads to specialized structures.
4. Nature of Growth in Plants
   In multicellular vascular plants, growth is indeterminate and continues throughout life.
5. Meristematic Regions
   Plant growth is restricted to specific regions called meristems, where cells divide continuously.
6. Types of Meristems
   Meristems are of three types based on location: apical (increase in length), intercalary (elongation of internodes), and lateral (increase in girth).

The increase in growth per unit time, indicating the efficiency of growth in plant organs, is called growth rate.

The measure that expresses the rate of increase in growth per unit time is called efficiency index.

The ratio of change in the number of cells (dn) over a given time interval (dt), representing total growth per unit time, is called absolute growth rate.

The growth rate of a system per unit time expressed on a common basis, obtained by dividing AGR by the total number of cells present, is called relative growth rate.

The permanent change in structure and function of meristematic cells leading to their maturation and specialization, with loss of capacity to divide, is called differentiation.

The process by which living, mature, differentiated cells regain the capacity to divide and become meristematic again, is called de-differentiation.

The process by which cells produced after de-differentiation once again lose the capacity to divide and become specialized to perform specific functions, is called re-differentiation.

The response of plants to the duration of light that influences flowering is called photoperiodism.

The induction or acceleration of flowering in plants by low temperature (chilling) treatment is called vernalization.

Plants that flower when the day length is shorter than the critical photoperiod and require a long uninterrupted dark period are called short day plants.

Plants that flower when the day length is longer than the critical photoperiod and require a short dark period are called long day plants.

Plants that flower independent of the duration of light are called day neutral plants.

The light-sensitive proteinaceous pigment present in leaves that perceives photoperiodic stimulus and regulates flowering is called phytochrome.

The reversal of the effect of vernalization by high temperature treatment is called devernalization.

The hypothetical chemical stimulus produced during vernalization and responsible for flowering is called vernalin.

• Mineral Nutrition
  The process by which plants absorb and utilize inorganic mineral elements from soil, water, and air for growth and development is called mineral nutrition.
• Source and Absorption
  Plants absorb minerals mainly from the soil in dissolved ionic form (e.g. PO₄³⁻, SO₄²⁻, CO₃²⁻) through roots.
• Essential Elements
  Plants require about 36–40 elements, of which some are essential for completing the life cycle and performing structural and physiological functions.
• Classification of Minerals
  Based on quantity required, minerals are classified into macroelements (required in large amounts) and microelements (required in trace amounts).
• Deficiency and Critical Concentration
  The minimum concentration of an essential element below which plant growth is affected is called critical concentration, and its shortage leads to deficiency.
• Deficiency Symptoms
  Common mineral deficiency symptoms include chlorosis, necrosis, stunting, mottling, and abscission, depending on the mobility of the element in plants.