Botanical description of hibiscus rosa sinensis notes

Botanical description of hibiscus rosa sinensis notes

Unknown   06:02   No comments:

Botanical description of hibiscus rosa sinensis notes

Habit:
     Perennial shrub.
Root:
     Tap root system.
Stem:
     Aerial, erect, cylindrical, woody and branched.
Leaf:
     Simple, Alternate, petiolate, stipulate, serrate, glabrous, apex acuminate with multicostate reticulate venation.
Inflorescence:
     Solitary cyme and axillary.
Flower:
     Pedicel jointed, bracteate, bracteolate, bisexual, large, showy, pentamerous, dichlamydeous, actinomorphic, complete and hypogynous and mucilage is present in floral parts.
Epicalyx:
    5 to 8 bracteoles outer to the calyx. They are green and free.
Calyx:
     Sepals 5, green, gamosepalous showing valvate aestivation and odd sepal is posterior in position.
Corolla:
     Petals 5, variously coloured, polypetalous but fused at the base and showing twisted aestivation. Androecium:
     Numerous stamens, monadelphous, filaments are fused to form a staminal tube around the style. Staminal tube is red. Anthers are monothecous, reniform, yellow, transversely attached to the filament, dehisce transversely and extrorse.
Gynoecium:
     Ovary superior, pentacarpellary and syncarpous. Ovary pentalocular with many ovules per locule on axile placentation. Style simple, long, slender and passes through the staminal tube. Stigma 5, capitate and coloured.
Fruit:
     Mostly abortive.

ECONOMIC IMPORTANCE
1. Fibre plants: 
     Gossypium barbadense (Egyptian cotton), G. hirsutum (American cotton), G. herbaceum (Cotton) and several other species of Gossypium yield cotton fibres of commercial value. The fibres are obtained from the surface of seeds. Hibiscus cannabinus (Deccan hemp) yields bast fibres which are used for making ropes.
2. Food plants: 
     The tender fruit of Abelmoschus esculentus (lady’s finger) is used as vegetable. The leaves and sepals of Hibiscus sabdariffa (A kind of ‘pulichai’) are used for making pickles, jam and jelly. A delicious ‘chutney’ is prepared from the leaves and sepals of H. cannabinus (Pulichai keerai) and H. sabdariffa.
3. Timber Plants: 
     Timber obtained from Thespesia populnea (portia tree) is useful for making boat, furniture and agricultural implements.
4. Medicinal plants: 
     Root and leaves of Abutilon indicum (Thuthi) and Malva sylvestris are used against fever. Roots of Malva sylvestris and Althaea rosea are used for treating whooping cough and dysentery respectively.
5. Ornamental plants: 
     Althaea rosea (Hollyhock), Hibiscus rosa-sinensis (Shoe flower) H. schizopetalus (A kind of shoe flower with dissected petals) are grown in gardens.

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MALVACEAE - the cotton family Notes

MALVACEAE - the cotton family Notes

Unknown   05:40   No comments:

MALVACEAE - the cotton family Notes

Systematic position:
     Class: Dicotyledonae
     Sub-class: Polypetalae
     Series: Thalamiflorae
     Order: Malvales
     Family: Malvaceae
General characters
Distribution:
    This family includes about 82 genera and more than 1,500 species. The plants are cosmopolitan in distribution, more abundant in tropical and subtropical regions. In India, Malvaceae is represented by 22 genera and 125 species.
Habit:
    Plants may be annual herbs ( eg. Malva sylvestris) or perennial shrubs (eg. Hibiscus rosa-sinensis) or trees (eg. Thespesia populnea). The members of this family have mucilagenous substance. Stellate hairs occur on their young parts.
Root:
    Tap root system.
Stem:
    Aerial, erect (eg. Malva sylvestris), branched, woody (eg. Thespesia populnea), decumbent as in Malva rotundifolia (Thirikalamalli) and usually covered with stellate hairs.
Leaf:
    Petiolate, simple, entire (eg. Thespesia populnea) or palmately lobed (eg. Gossypium arboreum), alternate, stipulate, margins usually toothed (eg. Hibiscus rosa-sinensis) and showing reticulate venation.
Inflorescence:
     Solitary, terminal (eg. Malvastrum coromendelia) or solitary, axillary (eg.Thespesia populnea) or terminal or axillary cyme.eg.Pavonia odorata (Peramutti).
Flower:
    Bracteate or ebracteate, bracteolate or ebracteolate, pedicellate, dichlamydeous, pentamerous, complete, actinomorphic, regular, bisexual and hypogynous.
Epicalyx:
     Bracteoles forming a whorl outer to calyx is called epicalyx. Bracteoles 3 in Malva sylvestris, 5 to 8 in Hibiscus rosa-sinensis, 10 to 12 in Pavonia odorata and absent in Abutilon indicum.
Calyx:
    Sepals 5, green, gamosepalous showing valvate aestivation.
Corolla:
     Petals 5, coloured, polypetalous but slightly fused at the base due to adhesion with staminal tube, regular and showing twisted aestivation.
Androecium:
     Numerous stamens, filaments are fused to form a staminal tube around the style and monadelphous. The staminal tube is fused with the petals at their bases. Anthers are monothecous, reniform, transversely attached to filaments and transversely dehiscent.
Gynoecium: 
     Ovary superior, two to many carpels but usually 5 to 10 carpels and syncarpous. Ovary with two to many locules. Pentacarpellary in Hibiscus rosa-sinensis, 10 in Althaea and 15 to 20 in Abutilon indicum. Number of locules usually corresponds to number of carpels. Each locule contains one to many ovules on axile placentation. Style long, slender and passes through the staminal tube ending in two to many distinct round stigmas.
Fruit:
     Loculicidal capsule e.g. Abelmoschus esculentus or schizocarp as in Abutilon indicum and Sida cordifoliaI (Nilathuthi).
Seed: 
     Endosperm is scanty, covered with hairs as in Gossypium barbadense.

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PLANT FUNCTIONS

PLANT FUNCTIONS

Unknown   07:48   No comments:

PLANT FUNCTIONS SCIENCE NOTES

PLANT FUNCTIONS:

     Plants germinate from seeds, grow, develop, mature, reproduce and die. They perform absorption, photosynthesis, respiration, transportation and transpiration. Plant physiology deals with how plants function.
     Water is essential for all physiological activities of plants. It plays an important role in physiological activities like photosynthesis, respiration, transpiration and transportation.
     The presence of water in the soil is essential for the normal functioning of plants. Soil water contains minerals in the dissolved state.
     Plants absorb water and minerals from the soil with the help of root hairs. This process is called absorption.

     The three different forces involved in absorption are:
     (i) Imbibition
     (ii) Diffusion
     (iii) Osmosis
i) Imbibition:
     Imbibition is the uptake of water by the substances that do not dissolve in water causing swelling of these substances. Eg.wood and seeds. These substances are called imbibants.
    In plant cells, the cell wall is the imbibant. It absorbs water and forms a channel for movement of water into the cell by diffusion and osmosis.
     Imbibition plays a very important role during germination. Seeds imbibe water through the seed coats. They swell and rupture, allowing the radicle and plumule to emerge.
ii) Diffusion: 
     Dissolved molecules move from a region of higher concentration to a region of lower concentration until the molecules are evenly distributed throughout the available space. Gases such as oxygen and carbon-dioxide, and nutrients like minerals move into cells by diffusion.
iii) Osmosis: 
     The movement of water molecule from a region of higher concentration to a region of lower concentration through a semi-permeable membrane is called osmosis.
Demonstration of Osmosis: 
     A potato is taken and peeled. The base is cut to make it flat. A hollow cavity is made in the centre of the tuber and filled with sugar solution. The initial level of solution is marked with the help of a pin. It is placed in a beaker containing coloured water.
     After sometime, it is observed that the sugar solution in the cavity of the potato becomes coloured and its level rises. How has this taken place? This is due to the entry of water from the beaker into the cavity of the potato through the living cells of the potato. Here the living cells of the potato act as a semi-permeable membrane.

     When substances move from a region of higher concentration to a region of lower concentration, without the use of metabolic energy, it is said to be passive transport. Active transport involves the use of metabolic energy for movement of molecules. The uptake of mineral ions is by active transport.
Ascent of Sap:
     Water, along with mineral salts, are absorbed by the root through its root hairs. The absorbed water reaches the xylem vessels and finally reaches the leaves. This movement of water and mineral salts is known as ascent of sap.
Demonstration of Ascent of Sap: 
     Take an entire balsam plant without damaging the roots. Wash the roots to remove the soil particles. Insert the roots into a bottle containing dilute eosin solution or red ink solution. Leave aside the set-up for sometime. After sometime, red streaks can be observed on the stem and veins of the leaves. If a section of the stem is mounted on a microscope and observed, it will show that only the xylem vessels are coloured, showing that ascent of sap takes place only through the xylem vessels.

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TISSUES SCIENCE NOTES

TISSUES SCIENCE NOTES

Unknown   07:26   No comments:

TISSUES SCIENCE NOTES

TISSUES:

Types, Structure and Function of Plant Tissues:

     The progressive evolution in plants has resulted in the increasing complexity of structures. In higher plants, roots, stems, leaves and flowers carry out different functions. Due to this division of labour, the cells of the plants are differentiated to form different tissues.
    The diagram given below shows the classification of different tissues:

Meristematic Tissues: 
     The growth of plants occurs only in certain specific regions. This is because the dividing tissue, also known as meristematic tissue (Meristos – divisible), is located only at these points.
     Meristematic tissues are made up of groups of similar and immature cells, which can divide and form new cells. Meristematic cells divide continuously and help in increasing the length and thickness of the plant. Depending upon their position, meristematic tissues can be of three types. They are as follows:
     i) Apical meristems: Apical meristem is present at the growing tips of stems and roots and increases the length of the plant body.
     ii) Intercalary meristems: These meristems occupy the base of leaves and the base of internodal regions in plants such as grasses (mostly in monocotyledonous plants). These help in the elongation of the internodes.
     iii) Lateral meristems: This includes the meristematic tissues that occupy the lateral regions of stems and roots. They bring about increase in the width of the plant body. (e.g. cork cambium and vascular cambium).

Characteristic features of meristematic tissues:

• The meristematic cells may be round, oval, polygonal or rectangular in shape. 
• Their cell walls are thin, elastic and made up of cellulose. 
• They are closely arranged without any intercellular spaces. 
• They have dense cytoplasm with large central nucleus.  

     What happens to the cells formed by meristematic tissues?

     Some cells produced by meristematic tissues stop dividing and form permanent tissues. 

Permanent Tissues: 

     They have definite structure and function. They are differentiated into various types according to the different functions they perform. 

Permanent tissues are classified as: 

     i) Simple tissues 

     ii) Complex tissues 

Simple Tissues:

      A tissue made up of cells having similar structure (one type of cells) and function is called simple tissue. They are of three types:

      a. Parenchyma

      b. Collenchyma

      c. Sclerenchyma

Parenchyma: 
     The cells of the parenchyma are generally thin-walled with intercellular spaces. They are living cells. They are present in all the organs of a plant. They may be oval, spherical, rectangular or cylindrical in shape. The cell wall is made of cellulose and pectin.
     Parenchyma cells serve to store and conduct food materials, water and minerals.
 Collenchyma: 
     The cells of collenchyma are polygonal in cross-section and have unevenly thickened walls. These thickenings are due to the deposition of cellulose, hemi-cellulose and pectin.
     The thickening is confined to the corners of the cells. They generally occur in the dicot stem in two or more layers below the epidermis. It is absent in the roots. It also occurs in the petiole and pedicel. Collenchyma is also a living tissue. The main function of the collenchyma is to provide strength and flexibility to the growing organs like the young stem.

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PLANT CELLS AND TRANSPORTATION

PLANT CELLS AND TRANSPORTATION

Unknown   07:08   No comments:

PLANT CELLS AND TRANSPORTATION

PLANT CELLS:

     Cells are the structural and functional units of all living organisms. The study of the structure and function of the cell is called Cytology or Cell biology.
     A plant cell is typically rectangular or cube shaped. It has an outer covering called cell wall which protects and gives it shape. A cell membrane, also known as the plasma membrane, surrounds the cytoplasm and its organelles. The plasma membrane, cytoplasm and the nucleus together are referred to as the protoplast. The cytoplasm carries various cell organelles like endoplasmic reticulum, mitochondria, chloroplast, Golgi bodies and ribosomes.
     Groups of cells having a common origin and performing similar functions are called tissues.

  TRANSPORTATION:

     The uptake and release of air, water, solutes and sap in plants involves transportation. It is a life process by which a substance, absorbed or made in one part of the body of an organism, is carried to the other parts of the body. Due to the branching shape of a plant, all the cells of a plant can get oxygen for respiration and carbon-dioxide for photosynthesis directly from the air by diffusion. Therefore the transport system primarily involves transport of water, minerals and food prepared in the leaves to the various parts of the plant.This is done through two specialized transport systems made of xylem and phloem cells.
     The transport of materials in a plant can be divided into two parts:
          i) Transport of water and minerals in the plant.
         ii) Transport of food and other substances like hormones in the plant.

Transport of Water and Minerals:

     Water and minerals are absorbed from the soil by the roots of the plant and transported to the various parts of the plant like stem, leaves and flowers. Water, along with the minerals dissolved in it, moves from the roots to the other parts through the two kinds of xylem cells called xylem vessels and tracheids.
     In pteridophytes and gymnosperms, tracheids are the only water conducting tissues.
     In angiosperms either xylem vessels or both xylem vessels and tracheids transport water.
     The movement of water and dissolved salts in the xylem is always upwards and it is caused by the suction of water at the top because of the low pressure created by transpiration from leaves.

Transport of Food and Other Substances:
     The transport of food from leaves to the other parts of the plant is called translocation. The movement of food materials through phloem depends on the action of living cells called sieve tubes.        Food is made in the mesophyll cells of a leaf. This enters into the sieve tubes of the phloem and is transported to all other parts of the plant body by the network of sieve tubes present inside the stem and roots.
     The movement of food in phloem can be upwards or downwards or lateral depending upon the needs of the plant.

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