Plant Growth and Development: Class 11 Biology NCERT Chapter 15

Key Features of NCERT Solutions for Class 11 Biology Chapter 15 – Plant Growth and Development

In the previous chapter 14: Respiration In Plants, you learnt about plants and understudies with understanding something very similar. It will cause you to see how the plants breathe.In this chapter: Plant Growth and Development, we will learn about the growth and development of the plants.

While growth stays to be one of the most fundamental qualities of every single living being, the one in plants is additionally basic. As it were, we can’t gauge the growth in plants effectively yet we realize it occurs. The manner in which plants create is a result of two things that are growth and separation. You may consider how does the structure of plants structure. All the plant’s organs are made of various tissues.

Besides, the section likewise clarifies the different pieces of plants like roots, leaves, natural products, and more appear. It talks about all seed germination and the earth required for it. Thus, the section will illuminate the plant growth controllers. You comprehend what plants need to grow yet there are additionally things that manage its growth. This is the thing that plant growth and improvement class 11 notes will disclose to understudies for a superior comprehension.

Sub-topics covered under Plant Growth and Development

  • Growth and its Phases–This area will acquaint understudies with the different stages and phases of a vegetation’s regarding growth. 
  • Plant Growth Regulators–Over here, understudies will find out about the characteristic variables which additionally help in the growth of plants. 
  • Photoperiodism–You will examine why certain plants just happen in specific seasons and why a few organic products bear in a particular season.
  • Vernalisation– The dependency of plants on the temperatures and how is what students will learn through this part.

 Quick revision notes

Much the same as some other living being, plants also grow in tallness and size after some time. So how does plant growth happen? Or then again how blossoms and natural products in a tree show up and fall intermittently? All occasions in plants, directly from the zygote stage to the full-grown plant happen in a precise way. This is called improvement. Improvement is the entirety of growth and separation. Let us comprehend plant growth and its stages in more detail.

Plant Growth And Its Phases

Growth is the most crucial trait of any living being. It is characterized as “an irreversible, perpetual increment in the size of an organ or its parts, or even of an individual cell”. By and large, growth is joined by metabolic procedures (catabolic and anabolic) that burn through effort.

Browse more Topics under Plant Growth And Development

  • Plant Growth Regulators
  • Photoperiodism
  • Vernalisation

Characteristics Of Plant Growth

Plant Growth Is Indeterminate

Plants have the one of a kind capacity to grow uncertainly for an amazing duration because of the nearness of ‘meristems’ in their body. Meristems have cells that can separation and self-spread. This is called ‘open type of growth’ in light of the fact that new cells are continually added to the plant body by the phones in the meristem. 

Meristems in the roots and shoots of plants are liable for ‘essential growth of the plant’. These expansion the stature of the plant. Then again, sidelong meristems increment the width of the plant. This is known as the ‘optional growth of the plant’

Plant Growth Is Measurable

At a cell level, growth basically implies an expansion in the measure of cellular material. Since this is difficult to gauge, growth is estimated in an amount corresponding to this expansion. Hence, growth is estimated regarding increment in cell number, region, volume, length and so forth. 

Did you realize that the cells in a watermelon can increment in size up to around multiple times! Then again, a solitary apical meristem in maize roots can create around 17,500 new cells for each hour! In the main case, growth is as far as the size of the cell while in the subsequent case, it is regarding cell number.

Phases Of Plant Growth

Meristematic Phase

The cells in the root and shoot zenith of a plant are continually partitioning. They speak to the meristematic period of growth. The cells in these locales have enormous cores and are wealthy in cellular material and their cell dividers are thin and contain cellulos.

Meristematic Phase

(Plant Growth and Development: Class 11)

Elongation Phase

The cells in the zone soon after the meristematic locale speak to the period of extension. The attributes of cells in this zone are cell augmentation, expanded vacuole arrangement and new cell divider statement.

Maturation Phase

Simply near the period of stretching, however away from the zenith lies the period of development. The cells in this locale arrive at their greatest size as for their cellular material and cell divider thickening.

Rates Of Growth

The growth rate is characterized as expanded growth per unit time. A life form or its parts can offer ascent to more cells in various manners. The expansion in growth might be number juggling or mathematical and in this way, the pace of growth can be communicated numerically.

Arithmetic Growth

Following mitotic cell division, only one cell continues to divide while the other begins to differentiate. A simple example of this is the elongation of a root at a constant rate. When you plot this increase in length against time, you get a linear curve as shown below. This is expressed mathematically as –

Lt = L0 + rt (where, Lt is the length at time ‘t’, L0 is the length at time ‘zero’, r is the growth rate)

Graphical representation

Geometric Growth

Most natural frameworks show an underlying growth stage which is moderate. This is the ‘slack stage’. This stage is trailed by a time of exponential growth and is called ‘log stage’ or ‘exponential stage’. Here, after mitotic cell division both the girl cells keep on isolating. 

Be that as it may, because of restricted supplement flexibly, the growth hinders offering ascend to the ‘fixed stage’. At the point when we plot this growth, we get a sigmoidal bend or S-bend as demonstrated as follows. This growth bend is ordinary for all cells, tissues, organs and is normal for a creature living in an indigenous habitat. Scientifically, it is communicated as – 

W1 = W0 ert (where W1 is last size, W0 is beginning size, e is base of regular logarithm, r is the growth rate and t is the hour of growth). Note: Here, r is the growth rate and is likewise the measure speaking to the capacity of the plant to create new plant material. This is the ‘proficiency record‘. 

Growth rate can likewise be portrayed as supreme or relative. The supreme growth rate is the estimation of all out growth per unit time. The relative growth rate is likewise the growth of a given framework for every unit time yet comparative with another boundary like beginning size, weight and so on.

Conditions For Growth

  • Water – Water is fundamental for cell expansion, augmentation and for keeping plant cells upstanding. It additionally gives the medium to enzymatic exercises which is required for growth. Accordingly, plant growth and its stages are exceptionally subject to water. 
  • Oxygen – Metabolic vitality is required for plant growth exercises. Oxygen assists with delivering this metabolic vitality. 
  • Supplements – Macro and micronutrients are wellsprings of vitality for plants. They are additionally expected to make cellular material. 
  • Light – Light controls growth and its stages in plants. 
  • Temperature – Every plant has an ideal temperature go appropriate for its growth. Changes in this range are unsafe to plant growth.

Differentiation, Dedifferentiation And Redifferentiation

Separation is the point at which the cells have quit isolating and are starting to develop and perform extraordinary capacities. For instance, to shape tracheids (prolonged cells that convey water in the xylem), the cells lose their cellular material. They likewise create solid, versatile cell dividers to convey water across significant distances. 

Dedifferentiation is where separated cells that have lost their capacity to partition, recover the ability to isolate under explicit conditions. Model – completely separated parenchyma cells can return to their prior meristem structure and gap. 

Redifferentiation is where dedifferentiated cells isolate and by and by produce cells that can no longer separation however develop to perform explicit capacities. Model – the meristems acquired after dedifferentiation (depicted above) can isolate and again produce cells that quit separating however proceed to develop. 

Much the same as growth, separation in plants is additionally open. This is on the grounds that cells that emerge from a similar meristem have various structures once they have developed. Likewise, the last structure of the cells at development is reliant on the area of the cell. For instance, cells that are away from the root apical meristem become root tops, while cells pushed to the outskirts become epidermis.

Plant Development

It is characterized as all the progressions that a life form experiences during its life cycle, directly from seed germination to senescence. Advancement of plants (for example growth and separation) is impacted by outward factors (light, temperature, water) and inherent variables (qualities and plant growth controllers). 

Plants react in various manners to condition and periods of life and offer ascent to various types of structures. This capacity of plants is called ‘pliancy’. Model – Leaves of a youthful cotton plant are distinctive fit as a fiddle from a develop cotton plant. Likewise, leaves of the buttercup plant that grow noticeable all around have an unexpected shape in comparison to those that grow in water. This marvel of creating various structures is called ‘heterophylly’.


Question: Name the initial slow phase of geometric growth?

  1. Elongation phase
  2. Lag phase
  3. Log phase
  4. Exponential phase

Solution: The answer is ‘b’. In geometric growth, the initially phase of slow growth is called ‘lag phase’.

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