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Q3(d):
Describe briefly:
(d) Absolute and relative growth rates
Solution :
Definition and Theoretical Framework
Growth in plants can be quantified using two distinct mathematical models: Absolute Growth Rate (AGR) and Relative Growth Rate (RGR). These metrics are essential for analyzing the efficiency of biological systems in converting resources into biomass over time.
Step 1: Analyzing Absolute Growth Rate (AGR)
Absolute Growth Rate represents the total increase in the size or weight of a plant organ or the entire plant body per unit time. It provides a measure of the net gain in biological material [Per biological growth analysis principles].
- Formula: $AGR = \frac{W_2 - W_1}{t_2 - t_1}$
- Variables: $W_1$ is the initial size/weight at time $t_1$, and $W_2$ is the final size/weight at time $t_2$.
- Characteristics: It is an additive measure of growth. It does not account for the initial size of the organ; therefore, two different plants may show the same AGR even if their growth efficiencies differ significantly.
Step 2: Analyzing Relative Growth Rate (RGR)
Relative Growth Rate, or the efficiency index, expresses the growth of a given system per unit of initial parameter. It measures the rate of growth of a system per unit of initial size [By standardized comparative growth metrics].
- Formula: $RGR = \frac{\text{Growth per unit time}}{\text{Initial size}} = \frac{W_2 - W_1}{W_1} \times 100$
- Characteristics: It is a ratio-based measure. It identifies the biological efficiency of a plant's growth process by normalizing the increase against the starting capacity.
Comparative Analysis Table
| Feature | Absolute Growth Rate (AGR) | Relative Growth Rate (RGR) |
|---|---|---|
| Definition | Total increase in growth over time. | Growth per unit of initial size. |
| Mathematical Nature | Additive (Difference). | Ratio (Percentage/Fractional increase). |
| Primary Utility | Quantifying total biomass accumulation. | Comparing growth efficiency between different organs/plants. |
Conceptual Visualization: Growth Dynamics
Final Solution: Absolute Growth Rate is the measurement of the total change in size ($W_2 - W_1$) over a time interval ($\Delta t$), whereas Relative Growth Rate is the measurement of this change expressed as a proportion of the original size ($\frac{W_2 - W_1}{W_1}$), serving as a vital metric for comparing growth efficiency across different plant developmental stages.
More Questions from Class 11 Biology Plant Growth and Development EXERCISES
- Q1: Define growth, differentiation, development, dedifferentiation, redifferentiation, determinate growth, meristem and growth rate.
- Q2: Why is not any one parameter good enough to demonstrate growth throughout the life of a flowering plant?
- Q3(a): Describe briefly: (a) Arithmetic growth
- Q3(b): Describe briefly: (b) Geometric growth
- Q3(c): Describe briefly: (c) Sigmoid growth curve
- Q4: List five main groups of natural plant growth regulators. Write a note on discovery, physiological functions and agricultural/horticultural applications of any one of them.
- Q5: Why is abscisic acid also known as stress hormone?
- Q6: ‘Both growth and differentiation in higher plants are open’. Comment.
- Q7: ‘Both a short day plant and a long day plant can produce can flower simultaneously in a given place’. Explain.
- Q8(a): Which one of the plant growth regulators would you use if you are asked to: (a) induce rooting in a twig
- Q8(b): Which one of the plant growth regulators would you use if you are asked to: (b) quickly ripen a fruit
- Q8(c): Which one of the plant growth regulators would you use if you are asked to: (c) delay leaf senescence
- Q8(d): Which one of the plant growth regulators would you use if you are asked to: (d) induce growth in axillary buds
- Q8(e): Which one of the plant growth regulators would you use if you are asked to: (e) ‘bolt’ a rosette plant
- Q8(f): Which one of the plant growth regulators would you use if you are asked to: (f) induce immediate stomatal closure in leaves.
- Q9: Would a defoliated plant respond to photoperiodic cycle? Why?
- Q10(a): What would be expected to happen if: (a) $GA_3$ is applied to rice seedlings
- Q10(b): What would be expected to happen if: (b) dividing cells stop differentiating
- Q10(c): What would be expected to happen if: (c) a rotten fruit gets mixed with unripe fruits
- Q10(d): What would be expected to happen if: (d) you forget to add cytokinin to the culture medium.
CBSE Solutions for Class 11 Biology Plant Growth and Development
Chapters in CBSE - Class 11 Biology
- The Living World
- Biological Classification
- Plant Kingdom
- Animal Kingdom
- Morphology of Flowering Plants
- Anatomy of Flowering Plants
- Structural Organisation in Animals
- Cell – The Unit of Life
- Biomolecules
- Cell Cycle and Division
- Transport in Plants
- Mineral Nutrition
- Photosynthesis
- Respiration in Plants
- Digestion and Absorption
- Breathing and Exchange of Gases
- Body Fluids and Circulation
- Excretory Products and Elimination
- Locomotion and Movement
- Neural Control and Coordination
- Chemical Coordination and Integration
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