Growth is a permanent and irreversible increase in the size or length of an organism observed through various metabolic processes. In plants, growth starts from seed germination, leading to seedling formation and eventually a mature plant. This chapter gives an overview of how plants grow, respond to their surroundings and use hormones to regulate growth. It explains the phases of plant growth and how plants adapt to environmental changes.
Students will know about important topics like the definition and process of plant growth, factors affecting growth and the role of growth regulators. The chapter also includes useful books and tips to strengthen understanding and prepare for exams. Solving the textbook questions and practising diagrams can help clarify key concepts and boost confidence for NEET and board exams. Plant Growth and Development is an important chapter in biology.
Important Topics of Chapter Plant Growth and Development:
Process of Plant Growth
Phases of Growth and Development
Plant Growth and Development Regulators
Important Concepts - Cell differentiation, Auxin, Gibberellins, Cytokinin
This chapter, Plant Growth and Development, specifies how plants grow and develop, with different growth stages under the influence of water, light, and minerals. The chapter focuses on plant hormones like auxins, gibberellins, cytokinins, ethylene, and abscisic acid, which control growth processes like germination and flowering. Concepts like photoperiodism and vernalization are introduced. This chapter helps us understand how plants grow and adapt to their surroundings.
Growth can be defined as a permanent increase in the size and mass of a plant and involves cellular enlargement and cell division. Development is a series of events that happen in the life history of a plant from germination through flowering, fruiting, and senescence. In this context, development refers to both, existence of a plant and reproductive success since it allows plants to produce seeds for the next generation.
Various factors influence the growth and development of plants, among which are genetic makeup, environmental conditions, and hormonal regulation. Other factors controllable or uncontrollable to man are the genetic make-up, the environmental conditions such as light, temperature, water, and nutrients, and hormonal regulation. Knowing and understanding all these would be of much help in maximising these agricultural practices for the sake of healthy plant development.
Also Read
Cell division is the basis of growth in plants. The phases of cell growth that happen in plants are described below-
Mitosis results in a process in which one cell divides and gives rise to two identical daughter cells that are mirror images of each other, and the process is used to help in growth, repair, and asexual reproduction in plants. Conversely, meiosis takes place in the reproductive organs of the organism and varieties of gametes, that is, the sperm and egg, to quickly enhance the ability of the species to carry on with the sexual means of reproduction.
Prophase: The chromosomes begin to condense and may now be visible.
Metaphase: The chromosomes align themselves align at the cell's equatorial plate.
Anaphase: Sister chromatids separate, moving toward opposite poles.
Telophase: Nuclear membranes form around each set of chromosomes.
Cytokinesis: The cleavage of the cell into two separate daughter cells.
The cells take up water, increase in volume, and tend to force the cell walls from the outside during cell turgor pressure. This is due to the water intake in the central vacuole, which causes the swelling of the cell.
Turgor pressure is the pressure exerted on the cell wall by the cell membrane; when this is absent, the cells are flaccid. It is therefore responsible for the turgidity of cells, hence cell enlargement. It is the result of the osmotic flow of water into a cell, and it provides the force for cell growth, leading to the extension of plant tissues.
Cell differentiation is simply a process in which the cells are differentiated into different cells, each having distinct functions. That, in turn, would make the process of cell differentiation extremely indispensable for the development of tissues and organs, which helps a plant carry on several of these kinds of complex activities like nutrient absorption, photosynthesis, and reproduction later on.
Example: Differentiation in Root and Shoot Systems
In the root system, cells differentiate into root hair cells, thus expanding the surface area for the absorption of water and nutrients. In the shoot system, cells differentiate into a variety of cell types, including xylem and phloem cells that function in water and nutrient transport and photosynthetic cells in leaves.
NCERT Books Link:
There are various stages of Plant Growth.
Imbibition: The seed imbibes water, swells, and the seed coat cracks.
Activation: Metabolic processes go active, enzymes are activated, and stored food reserves are mobilised.
Emergence of Radicle: First, the root appears and anchors the seedling. The radicle then begins to take water and nutrients.
Emergence of Plumule: The shoot is next to appear, growing directionally toward the light
Water: Important for the process of imbibition and the activation of enzymes.
Oxygen: This is required to provide energy for growth by respiration.
Temperature: It requires an optimum temperature for enzyme activity.
Light: Many seeds germinate in response to light, others in darkness.
Vegetative growth can be described as the stage at which the plant grows vegetatively to form root, stem, and leaf growth. This phase then eventually supports the reproductive growth of the plant.
Apical Meristems: found in the root and shoot apices; they account for primary growth; for elongation.
Lateral Meristems: the vascular and cork cambium; account for secondary growth; for thickening.
Intercalary Meristems: Found in the base of leaf blades or internodes; the cause for grass to sprout.
The phases in reproductive growth in plants include:
The process is accompanied by alteration of gene expression and hormonal regulation and forms the flowers, fruits, and seeds. The transition is often environmental, induced by stimuli such as light, temperature, and photoperiod, among others.
Flowering: the formation of flowers; these are essentially the sexual organs of the plant.
Fruiting: fruits, in post-fertilisation, are structures that primarily protect the seeds but aid in their dispersal as well.
Some major points are discussed below in the table:
Phases of Growth | Explanation |
Formative Phase |
|
Cell Enlargement and Differentiation |
|
Cell Maturation |
|
Leaf Development |
|
Root Development |
|
It is a process by which non-specialised cells get to be specialised to perform distinct functions.
It is the process of development which is important for developing most tissues and organs of plants. This gives way to complex structures and functions.
It is brought by both factors of genetic regulation and environmental signals.
Collenchyma Cells: They provide support and elasticity to young stems and leaves, respectively.
Sclerenchyma Cells: They provide mechanical support and strength with thick and lignified cell walls.
Roots: Development of root hairs that finally allow the absorption of water and its related nutrients.
Shoots: Differentiation processes that lead to the development of leaves, flowers, and fruits, and in transport tissue.
Leads to the formation of specialised structures like leaves, stems, and roots; in further vascular plants, it also leads to reproductive organs.
A means of coping with the environment, where cell differentiation leads the plant to develop its cells of a particular kind
Vascular Tissue: Xylem cells differentiate to conduct water and minerals while conducting sugars and other organic compounds is done by the phloem.
Specialised leaves: These leaves have mesophyll cells differentiated into palisade parenchyma for photosynthesis and spongy parenchyma for gas exchange.
NCERT Solutions Subject-wise link:
The environmental factors affecting plant growth and development are:
Light is one of the factors in photosynthesis, which is the process by which plants transform light energy into chemical energy to synthesise glucose and oxygen. Photoperiodism is responsible for the control of flowering, seed germination, and other developmental processes and is considered the plant's response to the length of day and night
Water maintains cell turgor and hence keeps the cells turgid, providing the plant with the erect form it holds. Water further acts as a solvent that acts in nutrient translocation between different parts of the plant through the xylem and phloem.
Effects of Water Deficiency and Excess
Water Deficiency: It results in wilting, stunted growth, and hampers physiological activities.
Water Excess: Root rotting, oxygen lack in the soil, and inhibition of nutrient uptake.
Temperature essentially changes the rate at which the enzymatic activities within the plants occur, affecting the growth and development of organisms. The optimal temperature ranges allow the maximum efficiency of the enzymatic activities and growth rate. Temperatures above or below could completely inhibit these functions from occurring altogether.
Plants need some macronutrients, such as nitrogen, phosphorus, and potassium, and other nutrients such as iron, manganese, and zinc, which are micronutrients, for development and to grow. These nutrients have their functionality in the physiological process.
Role of Soil Fertility in Plant Growth
Soil fertility can be defined as a state where the soil possesses all the required nutrients for plant growth. Such a soil with required nutrients will support the profuse growth of plants by developing a healthy, competent root system that can pick up the required nutrients from the environment at a fast rate.
Some important growth regulators of plants are discussed below with their specific roles mentioned along with them.
Plant Growth Regulators | Explanation |
Auxin |
|
Cytokinin |
|
Gibberellins |
|
Abscisic Acid (ABA) |
|
Ethylene |
|
NCERT Notes Subject Wise Link:
It's hard to remember everything in a single go. We made the entire problem easy. Some of the tricks regarding Plant growth and Development are given below which you can use to memorize the important points.
FEDC
F: Formative Phase (Cell division through mitosis)
E: Enlargement Phase (Cell growth, water absorption, vacuole formation)
D: Differentiation Phase (Cells attain specific structure and function)
C: Cell Maturation (Enlarged cells reach full shape and function)
LWTN
L: Light (Photosynthesis, flowering, stomatal movement)
W: Water (Hydration, nutrient transport, photosynthesis)
T: Temperature (Affects photosynthesis, germination, transpiration)
N: Nutrients (Macronutrients like N, P, K, micronutrients like Fe, Cu)
AGECE
A: Auxin (Cell elongation, root initiation, apical dominance)
G: Gibberellins (Stem elongation, seed germination, breaking dormancy)
E: Ethylene (Fruit ripening, leaf abscission, stress response)
C: Cytokinin (Cell division, shoot formation, delay leaf aging)
E: Abscisic Acid (ABA) (Promotes dormancy, stress response, inhibits growth)
NCERT Exemplar Solutions Subject-wise link:
The table given below indicates the weightage and types of questions asked from plant growth and development in exams:
Exam Type | Types of Questions | Weightage |
Short answer questions on plant hormones, phases of growth, seed germination, and factors affecting plant growth. | 5-6% | |
MCQs cover plant hormones (auxins, gibberellins, cytokinins, etc.), photoperiodism, vernalization, and growth curves. | 3-4% | |
Assertion and reason questions on plant growth regulators, tropic movements, and factors affecting development. | 3-4% | |
Scenario-based questions on plant growth patterns, hormonal control of development, and the use of plant hormones in healthcare. | 2-3% | |
True/False and MCQs on plant growth stages, roles of hormones, dormancy, and development-related processes. | 1-3% |
The main and most recommended learning resource for plant growth and development is the NCERT Biology class 11 textbook covering all concepts as per the CBSE syllabus. For further understanding, "Trueman's Elementary Biology, Volume 1" can be referred to. The other useful book is "Pradeep's Biology" which is also known for its detailed explanation and plenty of solved examples. You can access a variety of videos, articles and mock tests on this chapter from the careers360 platform. These books along with proper practice will help a lot for board exams as well as competitive exams like NEET.
Also Read
Plant growth is a process characterised by the irreversible change in the size of cells and plant parts that is a result of cell division and enlargement. Plant development is the process of progression from seed germination to maturation.
18 Sep'24 06:15 PM
18 Sep'24 03:49 PM
28 Aug'24 10:01 AM
27 Aug'24 04:12 PM
27 Aug'24 04:08 PM
27 Aug'24 04:05 PM