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Anatomy of Flowering Plants NCERT Textbook With Solutions PDF Free Download
Chapter 6: Anatomy of Flowering Plants
You can very easily see the structural similarities and variations in the external morphology of the larger living organism, both plants, and animals.
Similarly, if we were to study the internal structure, one also finds several similarities as well as differences.
This chapter introduces you to the internal structure and functional organization of higher plants.
The study of the internal structure of plants is called anatomy. Plants have cells as the basic unit, cells are organized into tissues and in turn, the tissues are organized into organs.
Different organs in a plant show differences in their internal structure.
Within angiosperms, the monocots and dicots are also seen to be anatomically different. Internal structures also show adaptations to diverse environments.
6.1 The Tissue
A tissue is a group of cells having a common origin and usually performing a common function. A plant is made up of different kinds of tissues.
Tissues are classified into two main groups, namely, meristematic and permanent tissues based on whether the cells being formed are capable of dividing or not.
6.1.1 Meristematic Tissues
Growth in plants is largely restricted to specialized regions of active cell division called meristems (Gk. meristos: divided).
Plants have different kinds of meristems. The meristems which occur at the tips of roots and shoots and produce primary tissues are called apical meristems.
Root apical meristem occupies the tip of a root while the shoot apical meristem occupies the distant most region of the stem axis.
During the formation of leaves and elongation of the stem, some cells ‘left behind’ from shoot apical meristem, constitute the axillary bud.
Such buds are present in the axils of leaves and are capable of forming a branch or a flower.
The meristem which occurs between mature tissues is known as intercalary meristem. They occur in grasses and regenerate parts removed by the grazing herbivores.
Both apical meristems and intercalary meristems are primary meristems because they appear early in the life of a plant and contribute to the formation of the primary plant body.
The meristem that occurs in the mature regions of roots and shoots of many plants, particularly those that produce woody axis and appear later than primary meristem is called the secondary or lateral meristem.
They are cylindrical meristems. Fascicular vascular cambium, interfascicular cambium and cork-cambium are examples of lateral meristems.
These are responsible for producing secondary tissues.
Following divisions of cells in both primary and as well as secondary meristems, the newly formed cells become structurally and functionally specialized and lose the ability to divide.
Such cells are termed permanent or mature cells and constitute permanent tissues. During the
formation of the primary plant body, specific regions of the apical meristem produces dermal tissues, ground tissues, and vascular tissues.
6.1.2 Permanent Tissues
The cells of the permanent tissues do not generally divide further. Permanent tissues having all cells similar in structure and function are called simple tissues. Permanent tissues having many different types of cells are called complex tissues.
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NCERT Solutions Class 11 Biology Chapter 6 Anatomy of Flowering Plants
1. Cork cambium forms tissues that form the cork. Do you agree with this statement? Explain.
Yes, cork cambium forms tissues that in turn form the cork. When the stem increases in girth, another meristematic tissue known as phellogen or cork cambium grows in the cortex region of the stem. This phellogen cuts off cells on both sides.
The outer cells differentiate into the phellem or the cork while the inner cells differentiate into the phelloderm or secondary cortex. The cork is impermeable to water because of suberin, rendering protection to the tissues underneath.
2. Explain the process of secondary growth in the stems of woody angiosperms with the help of schematic diagrams. What is its significance?
The primary xylem and phloem exhibit the presence of a strip of cambium in woody dicot roots known as the interfascicular cambium which is formed from the cells of the medullary rays connecting the interfascicular cambium.
Hence, the continuous cambium ring is formed. The cambium separates from the newly formed cells on either side while the cells found towards the exterior differentiate into the secondary phloem. The cells detach towards the pith giving rise to the secondary xylem. The secondary xylem is synthesized in excess compared to the secondary phloem.
When there is secondary growth in plants, the girth of the plant increases, along with an increase in the water content and nutrients in order to assist the ever-growing leaves, rendering support to the plants.
3. The transverse section of a plant material shows the following anatomical features – (a) the vascular bundles are conjoint, scattered, and surrounded by a sclerenchymatous bundle sheath. (b) phloem parenchyma is absent. What will you identify it as?
The traverse section is of Monocot stem. It is because the vascular bundles are dispersed in monocot stems. The phloem parenchyma is not found.
4. Why are xylem and phloem called complex tissues?
Xylem and Phloem are called complex tissues because they are made of more than one type of cell which works together as a unit to perform the function. Xylem transports water while phloem transports food.
5. What is stomatal apparatus? Explain the structure of stomata with a labeled diagram.
Stomata are structures present in the epidermis of leaves. Stomata regulate the process of transpiration and gaseous exchange. Each stoma is composed of two bean-shaped cells known as guard cells which enclose the stomatal pore.
Guard cells are dumbbell-shaped, where their outer wall is thin and the inner wall is highly thickened. These structures possess chloroplasts and regulate the closing and opening of the stomata.
The epidermal cells near the guard cells in some cases become specialized in their structure shape and size, they are referred to as subsidiary cells. The guard cells, the stomatal aperture, and girdling subsidiary cells are collectively referred to as the stomatal apparatus.
6. How do the various leaf modifications help plants?
Leaves fundamentally perform photosynthesis. But in some plants, leaves are modified to carry out different functionalities, mentioned below:
Tendrils: Tendrils helps for climbing as in peas
Spines: Thorns are modified leaves that will protect plants from animals, serving as an organ of defense.
Pitcher: Leaves of this plant are modified into pitcher-like structures containing digestive juices aiding in trapping and digesting insects.
Synthesis of food: Fleshy leaves of garlic and onion store some food. These are modified leaves. Phyllodes emerging from the petioles of leaves synthesize food. Phyllodes are flattened, green structures that replace the short-lived leaves.
7. Define the term inflorescence. Explain the basis for the different types of inflorescence in flowering plants.
The inflorescence is the arrangement of flowers on the floral axis.
There are two major types of inflorescence depending upon whether the apex is converted into a flower or continues to grow, they are:
Racemose: Type of inflorescence in which the flowers are borne laterally in acropetal succession, i.e, newer flowers are near the apex while older flowers are at the base. The main axis continues to grow.
NCERT Class 11 Biology Textbook Chapter 6 Anatomy of Flowering Plants With Answer PDF Free Download