, r) / M% What isground tissue, whereisit found and whatfunctionsaoes it have? 4
ID: 212894 • Letter: #
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, r) / M% What isground tissue, whereisit found and whatfunctionsaoes it have? 4 cribe the structure and functions of parenchyma, collenchyma, and sclerenchyma ni What does meristem tissue do? What is primary and secondary growth and wha meristems produce them? ued rin re zones are responsible for primary growth at the root tip? What happens ip each zone? stems andI 9. How does the arrangement of vascular tissues differ in monoeois and eudicots? 10. What types of cells make up the photosynthetic tissue in leaves? How are they 11. Give a thorough explanation of vascular cambium. What is it? Where is it? What does 12. What does bark consist of and how and where were those cells produced? Whatliad arranged in most leaves? it do? How does it do it? functions does bark have?Explanation / Answer
Answer:
4).
Ground tissue system (GTS):
The ground tissue system occupies greater portion of the plant body, than the other two tissue systems, namely epidermal and vascular tissue systems. In primary plant body of stems and roots, it comprises the whole of cortex and part of stele i.e. hypodermis, general cortex, endodermis, pericycle, pith and pith rays. However, these regions are not clearly demarcated in monocot stems. The GTS is made up of simple tissue, mostly the parenchyma. In leaves, the GTS is known as mesophyll, which may be further distinguished into palisade and spongy tissues. The parenchyma surrounding the vascular bundles of the leaf is known as bundle parenchyma and sclerenchymatous patches also when present are GTS only.
The functions of ground tissue system vary with type of the tissues and position. The different functions include protection, storage, support, assimilation and transport.
5).
A simple tissue is made of only one type of cells. The various simple tissues in plants are parenchyma, collenchyma and sclerenchyma. Except sclerenchyma the other two tissues are living.
Parenchyma
It forms the major component within the organs. The body of the lower organisms (e.g.: bryophytes) is wholly made up of this tissue. Therefore, it is known as ground or fundamental tissue. The cells of the parenchyma are generally isodiametric. They may be spherical, oval, round, polygonal or elongated in shape. Their walls are thin and made up of cellulose. They may either be closely packed or have small intercellular spaces. The mature cells have vacuoles.
Parenchyma is found in different forms in higher plants. Parenchyma cells having chloroplasts (as found in leaves) are referred to as chlorenchyma. Parenchyma with large intercellular spaces forming network (as in water lilies and other aquatic plants) is called aerenchyma. Parenchyma meant for storage of food material like starch, protein or oils (soft edible parts of fruits, vegetables and seeds) or mucilaginous substances and water as in xerophytes is called storage parenchyma.
Functions of parenchyma:
Collenchyma
It occurs in layers below the epidermis in stems and petioles of dicotyledonous plants. It is in the form of continuous or discontinuous ring. It consists of cells which are much thickened at the corners due to the deposition of cellulose, hemicellulose and pectin. The cells are elongated, round, cylindrical and vacuolated. Collenchymatous cells may be oval, spherical or polygonal and often contain chloroplasts. Apart from chloroplasts they contain tannins. Collenchyma may be of angular, lacunar, or lamellar type.
Functions of collenchyma:
Sclerenchyma
It is a mechanical tissue composed of dead cells (without protoplasts at maturity). It is present in different parts of the plant body and helps in overcoming stress and weight.
It consists of long, narrow cells with thick and lignified cell walls having a few or numerous pits. The cell wall is made up of cellulose and lignin. Inside the cell there is a long narrow lumen in the centre.
On the basis of variation in form, structure, origin and development, sclerenchyma occurs as either fibres or sclereids. The fibres generally occur in groups in various parts of the plant. The are thick-walled, elongated and pointed cells much longer than the width; having proportionately tiny cavity. The lumen runs throughout the length of the fiber. Fibers are commercially useful in the manufacturing of cloth, threads, ropes etc.
The sclereids or stone cells are spherical, oval or cylindrical, highly thickened dead cells with very narrow cavities (lumen). These are commonly found in the fruit walls of nuts; pulp of fruits like guava, pear and sapota; seed coats of legumes and leaves of tea. On the basis of shape the sclereids are classified into Brachy, Osteo, Astero, Macro and Trichosclereids.
Functions of sclerenchyma:
6).
MERISTEMATIC TISSUE (MERISTEM):
The plants have permanent region of growth called meristems or meristematic tissues which is absent in animals. It is an undifferentiated tissue from which new cells are formed. The group of cells of meristematic tissue is always in a state of division and persists from embryonic stage. Differentiated plant cells generally cannot divide or produce cells of a different type. Therefore, cell division in the meristems is required to provide new cells for expansion and differentiation of tissues and initiation of new organs, providing the basic structure of the plant body.
These meristems are responsible for primary growth, or an increase in length or height.
The meristem which occurs between mature tissues is known as intercalary meristem. They occur in grasses and regenerate the parts removed by the grazing herbivores. Both apical meristems and intercalary meristems are primary meristems because they appear early in life of a plant and contribute to the formation of the primary tissues that causes an increase in the plant body length. 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. Fascicular vascular cambium (or intrafascicular cambium), interfascicular cambium and cork-cambium are examples of lateral meristems. These are responsible for producing the secondary tissues and thereby increasing the diameter of the plant body resulting in the increase of the girth of roots and stems.
The cells newly formed by both primary and secondary meristems become structurally and functionally specialized. Such cells lose the ability to divide. They are called permanent or mature cells of the tissues.
7).
Regions of the Root
1. The root is covered at the apex by a thimble-like structure called the root cap. It protects the tender apex of the root as it makes its way through the soil.
2. A few millimeters above the root cap is the region of meristematic activity. The cells of this region are very small, thin-walled and with dense protoplasm. They divide repeatedly.
3. The cells proximal to this region undergo rapid elongation and enlargement, and are responsible for the growth of the root in length. This region is called the region of elongation. The cells of the elongation zone gradually differentiate and mature. Hence, this zone, proximal to region of elongation, is called the region of maturation. From this region some of the epidermal cells form very fine and delicate, thread-like structures called root hairs. These root hairs absorb water and minerals from the soil.
Functions of a Root: The main functions of root system are: Absorption of water and nutrients from soil, proper anchorage and synthesizing growth regulators.
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