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Plant Growth and Development - Development

Grade 11CBSEBiology

Review the key concepts, formulae, and examples before starting your quiz.

🔑Concepts

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Development is a process that includes all changes an organism goes through during its life cycle, from seed germination to senescence. It is the sum of growth and differentiation: Development=Growth+DifferentiationDevelopment = Growth + Differentiation.

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The sequence of developmental process in a plant cell includes: Plasmatic growth →\rightarrow Differentiation →\rightarrow Maturation →\rightarrow Senescence →\rightarrow Death.

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Plasticity is the phenomenon where plants follow different pathways in response to environment or phases of life to form different kinds of structures. Examples include heterophylly in cotton, coriander, and larkspur.

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Environmental Heterophylly is observed in plants like buttercup (RanunculusRanunculus), where the leaves produced in air are different from those produced in water.

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Development is controlled by intrinsic factors (including genetic factors and plant growth regulators like AuxinsAuxins, GibberellinsGibberellins, CytokininsCytokinins, ABAABA, and EthyleneEthylene) and extrinsic factors (light, temperature, water, oxygen, and nutrients).

📐Formulae

Development=Growth+DifferentiationDevelopment = Growth + Differentiation

Lt=L0+rtL_t = L_0 + rt

W1=W0ertW_1 = W_0 e^{rt}

AGR=dwdtAGR = \frac{dw}{dt}

RGR=W1−W0W0×tRGR = \frac{W_1 - W_0}{W_0 \times t}

💡Examples

Problem 1:

Two leaves, A and B, are growing. Leaf A grows from 5 cm25\text{ cm}^2 to 10 cm210\text{ cm}^2 in one day. Leaf B grows from 50 cm250\text{ cm}^2 to 55 cm255\text{ cm}^2 in one day. Calculate the Absolute Growth Rate (AGR) and Relative Growth Rate (RGR) for Leaf A.

Solution:

For Leaf A: Initial size (W0W_0) = 5 cm25\text{ cm}^2 Final size (W1W_1) = 10 cm210\text{ cm}^2 Time (tt) = 1 day1\text{ day}

Calculation for Absolute Growth Rate: 10−55\begin{array}{r} 10 \\ - 5 \\ \hline 5 \end{array} AGR=5 cm2/dayAGR = 5\text{ cm}^2/\text{day}

Calculation for Relative Growth Rate: RGR=W1−W0W0×100RGR = \frac{W_1 - W_0}{W_0} \times 100 RGR=55×100=100%RGR = \frac{5}{5} \times 100 = 100\%

Explanation:

The Absolute Growth Rate is the total growth per unit time. The Relative Growth Rate is the growth per unit time expressed per unit initial parameter. Even though both leaves have the same AGR (5 cm2/day5\text{ cm}^2/\text{day}), Leaf A has a much higher RGR because its initial size was smaller.

Development Class 11 Notes & Examples | CBSE Biology