NCERT Class 12 Books Biology Chapter 2- Sexual Reproduction in Flowering Plants

Safalta Expert Published by: Noor Fatima Updated Wed, 29 Jun 2022 11:56 PM IST

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Here is the information about NCERT Class 12 Books Biology Chapter 2. You can give a read to this blog and get PDFs of the subject. 
 

NCERT Class 12 Books Biology Chapter 2- Sexual Reproduction in Flowering Plants is accessible here for download purposes. You can download the PDF for and learn from the book anytime you want. Students who are studying in Class 12 and candidates who are preparing for competitive exams can download the PDF for NCERT Class 12 Books Biology Chapter 2- Sexual Reproduction in Flowering Plants to learn from the reading material.  

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SEXUAL REPRODUCTION IN FLOWERING PLANTS

Are we not lucky that plants reproduce sexually? The myriads of flowers that we enjoy gazing at, the scents and the perfumes that we swoon over, the rich colours that attract us, are all there as an aid to sexual reproduction. Flowers do not exist only for us to be used for our own selfishness. All flowering plants show sexual reproduction. A look at the diversity of structures of the inflorescences, flowers and floral parts, shows an amazing range of adaptations to ensure formation of the end products of sexual reproduction, the fruits and seeds. In this chapter, let us understand the morphology, structure and the processes of sexual reproduction in flowering plants (angiosperms).


2.1 FLOWER – A FASCINATING ORGAN OF ANGIOSPERMS

Human beings have had an intimate relationship with flowers since time immemorial. Flowers are objects of aesthetic, ornamental, social, religious and cultural value – they have always been used as symbols for conveying important human feelings such as love, affection, happiness, grief, mourning, etc. List at least five flowers of ornamental value that are commonly cultivated at homes and in gardens. Find out the names of five more flowers that are used in social and cultural celebrations in your family. Have you heard of floriculture – what does it refer to? To a biologist, flowers are morphological and embryological marvels and the sites of sexual reproduction. In class XI, you have read the various parts of a flower. Figure 2.1 will help you recall the parts of a typical flower. Can you name the two parts in a flower in which the two most important units of sexual reproduction develop? 


2.2 PRE-FERTILISATION: STRUCTURES AND EVENTS

Much before the actual flower is seen on a plant, the decision that the plant is going to flower has taken place. Several hormonal and structural changes are initiated which lead to the differentiation and further development of the floral primordium. Inflorescences are formed which bear the floral buds and then the flowers. In the flower the male and female reproductive structures, the androecium and the gynoecium differentiate and develop. You would recollect that the androecium consists of a whorl of stamens representing the male reproductive organ and the gynoecium represents the female reproductive organ.


2.2.1 Stamen, Microsporangium and Pollen Grain

Figure 2.2a shows the two parts of a typical stamen – the long and slender stalk called the filament, and the terminal generally bilobed structure called the anther. The proximal end of the filament is attached to the thalamus or the petal of the flower. The number and length of stamens are variable in flowers of different species. If you were to collect a stamen each from ten flowers (each from different species) and arrange them on a slide, you would be able to appreciate the large variation in size seen in nature. Careful observation of each stamen under a dissecting microscope and making neat diagrams would elucidate the range in shape and attachment of anthers in different flowers.
A typical angiosperm anther is bilobed with each lobe having two theca, i.e., they are dithecous (Figure 2.2 b). Often a longitudinal groove runs lengthwise separating the theca. Let us understand the various types of tissues and their organisation in the transverse section of an anther (Figure 2.3 a). The bilobed nature of an anther is very distinct in the transverse section of the anther. The anther is a four-sided (tetragonal) structure consisting of four microsporangia located at the corners, two in each lobe.

The microsporangia develop further and become pollen sacs. They extend longitudinally all through the length of an anther and are packed with pollen grains.

Structure of microsporangium: In a transverse section, a typical microsporangium appears near circular in outline. It is generally surrounded by four wall layers (Figure 2.3 b)– the epidermis, endothecium, middle layers and the tapetum. The outer three wall layers perform the function of protection and help in dehiscence of anther to release the pollen. The innermost wall layer is the tapetum. It nourishes the developing pollen grains. Cells of the tapetum possess dense cytoplasm and generally have more than one nucleus. Can you think of how tapetal cells could become bi-nucleate? When the anther is young, a group of compactly arranged homogenous cells called the sporogenous tissue occupies the centre of each microsporangium. 


NCERT Class 12 Books Biology Chapter 2- Sexual Reproduction in Flowering Plants- PDF Download

Chapter 2: Sexual Reproduction in Flowering Plants

अध्याय 2: पुष्पी पादपों में लैंगिक जनन

Where can you download NCERT Class 12 Books Biology Chapter 2 PDF?

Candidates can download NCERT Class 12 Books Biology Chapter 2- Sexual Reproduction in Flowering Plants PDF for free on our page. Links are given below.

Chapter 2: Sexual Reproduction in Flowering Plants

अध्याय 2: पुष्पी पादपों में लैंगिक जनन

Why is NCERT Books Class 12 Biology the best study material?

The book can also help in clarifying doubts. Other benefits of studying from the NCERT Books Class 12 Biology are-
  • Students gain profound knowledge about Biology through the NCERT Books Class 12 Biology
  • The course books contain pictures that can help students in better understanding of the Chapter 2s
  • These books can help students in self-study

Why is NCERT Books Class 12 Biology so recommended for board exams?

Almost all the questions that appear in board exams are from NCERT Books Class 12 Science. Moreover, a team of professional teachers drafts these books, which become a reliable source of study for students.
 

Are CBSE Books for Class 12 Biology important from an examination perspective?

The Chapter 2s in CBSE Books for Class 12 Biology are vital for board exams and higher classes. Students should read the Unit given in the CBSE books for Class 12 Science. These stories and practice questions can help gain excellent marks.

To get outstanding marks, we provide mock test papers that can help gear-up your preparations for exams. Additionally, you can also download e-books to get yourself prepared even in a better way.
 

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