ICSE Class 10 Biology Chapter 04 Absorption by Roots The Processes Involved

Are you looking for the ICSE Class 10 Biology book PDF free download. You have come to the right place as we have provided the PDF for Chapter 4 Absorption by Roots The Processes Involved here. You can refer to the link below to download the ICSE Class 10 Biology Book in PDF Chapter 4 Absorption by Roots The Processes Involved which is highly recommended textbook for students following the ICSE syllabus for this year. This book has been published by Selina Concise for this academic year and covers important concepts in a detailed manner. Students of ICSE Class 10 will be easily able to understand all concepts and will help students to build a strong foundation in the subject. One of the key chapters in this book is Chapter 4 Absorption by Roots The Processes Involved which explains all the important topics in lot of detail. The Biology book for Class 10 follows the latest ICSE syllabus for the current year thus ensuring that students get updated with the most relevant content for their studies. By downloading the Selina Concise Biology Class 10 Textbook PDF, students can conveniently access the book anytime and study without needing a physical copy.

Syllabus

(i) Absorption by roots; imbibition; diffusion and osmosis; osmotic pressure; root pressure; turgidity and flaccidity; plasmolysis and deplasmolysis, the absorption of water and minerals, active and passive transport (in brief); the importance of root hair.

(ii) The rise of water up to the xylem; a general idea of cohesive, adhesive forces and transpirational pull; demonstrated by the use of dyes.

Scope of syllabus: Characteristics of roots, which make them suitable for absorbing water, should be discussed with the process of absorption. Structure of a full-grown root hair should be explained. Experiments to show the conduction of water through the xylem should be discussed. Mention of the causative forces must be made for better understanding but as per the syllabus.

Plant physiology is the branch of biology which deals with the life functions of the plant. It includes the functioning of cells, tissues, organs, organ-systems and the organism as a whole. This chapter deals with some of the most fundamental processes like osmosis, which have tremendous significance in the life of all organisms.

4.1 Absorption by the Roots

The roots fix the plant in the soil giving it support but the most important and life-supporting function of the roots is to absorb

(A) water and

(B) mineral nutrients from the soil,

and conduct them into the stem for supply to the leaves, flowers, fruits, etc.

4.2 Need of Water and Minerals for Plants

A. Need of water

Besides being a constituent of protoplasm, water is needed inside the plant body for four purposes: photosynthesis, transpiration, transportation and mechanical stiffness.

1. Photosynthesis: Water is used up in the green leaves as a raw material in the synthesis of glucose.

2. Transpiration: A large quantity of water is passed out as water vapour during transpiration, for cooling in hot weather, for producing a suction force, etc.

3. Transportation: Transportation of substances in water solution from the roots upward into the shoot (mineral salts) or from leaves to other parts (sugar, etc).

4. Mechanical stiffness: Water provides turgidity (fully distended condition), which is necessary for the stiffness of plant tissues.

B. Need of mineral nutrients

Mineral nutrients required by the plant are absorbed from the soil by the roots only. Some of these nutrients are absorbed as salts (nitrates, phosphates, sulphates, etc.) and some simply as ions (potassium, calcium, magnesium, chlorine, etc.). These elements are required as constituents of cell and cell organelles as well as in the synthesis of a variety of compounds or enzymes within the cell.

4.3 Characteristics of Roots for Absorbing Water

The ability of the roots to draw water from the soil is dependent on three characteristics: (i) a huge surface area provided by rootlets and root hairs, (ii) root-hairs containing the solution (cell sap) at a concentration higher than that of the surrounding soil water and (iii) root hairs having thin walls.

(i) Surface area of roots is enormous (Fig. 4.1). It is a common experience that even a small garden plant such as balsam, when gently uprooted from the soil, shows a thick bunch of rootlets (branch roots). When carefully examined, each rootlet would show hundreds of root hairs. If all the root hairs of this plant were to be laid end to end, they would cover a length of many kilometres.

A botanist H.J. Dittmer (1937) worked out that a four-month-old rye plant had an aggregate root length of about 600 km. The number of root hairs in it exceeded 14 billion and their estimated total length would even exceed 10,000 km. Thus, altogether, the roots of any plant provide a huge surface area to facilitate the absorption of water.

(ii) Root-hairs contain cell sap, of a higher concentration than that of the surrounding water. Root hairs are the extensions of the outer (epidermal) cells of the root. They also contain large vacuoles filled with a sort of solution called cell sap. Some salts are dissolved in it and the cell sap, therefore, usually has a concentration higher than that of the surrounding water. This characteristic is an important requirement to draw in the outside water, i.e. for the occurrence of osmosis, which is described later.

(iii) Root-hairs have thin walls. Like all plant cells, root-hairs also have two outer layers - a cell wall and a cell membrane (Fig. 4.2).

- The cell wall is thin and permeable. It allows the movement of water molecules and dissolved substances freely in and out of the cell.

- The cell membrane is very thin, and semi-permeable, which means that it allows water molecules to pass through, but not the larger molecules of the dissolved salts. The secret of the absorption of water from the soil by the roots lies mainly in this characteristic.

Progress Check

1. List the three primary functions of root.

(i) .....................................................................

(ii) .....................................................................

(iii) .....................................................................

2. Mention four purposes for which the plants need water.

(i) .....................................................................

(ii) .....................................................................

(iii) .....................................................................

(iv) .....................................................................

3. Where are the mineral nutrients mostly used in plants?

..........................................................................

4. List three main characteristics of the roots that suit them to draw water from the soil.

(i) .....................................................................

(ii) .....................................................................

(iii) .....................................................................

This is a preview of the first 2 pages. To get the complete book, click below.

Click the link below to download the ICSE Class 10 Biology Chapter 4 Absorption by Roots The Processes Involved in PDF