STUDY OF STEM, ROOT, LEAF, SEED, FRUIT, FLOWER AND THEIR MODIFICATIONS : STUDY OF CELL AND ITS INCLUSIONS: BP112RBP REMEDIAL BIOLOGY Practical
Aim:
To study the general morphology of root, stem, leaf, seed, fruit, flower and their modifications.
Requirements:
Fresh or museum specimens, model of specimens, Photographs or pictures of specimens of roots, stem, leaf, seeds, fruit, flower.
Observations:
- LEAF:
Theory: The leaf is the most important vegetative organ of the plant. It is a lateral appendage borne at nodes of stem and is associated with photosynthesis, gaseous exchange, and transpiration Despite its wide variety in shapes, sizes and form, leaves of many plant species are also modified to perform some other special functions. These are called leaf modifications Some of the leaf modifications are:
1. Leaf tendrils, 2. Leaf hooks, 3. Leaf spines, 4. Phyllode, 5. Leaf pitcher, 6. Leaf Bladder
1. Leaf Tendrils: These are thin and sensitive thread-like structures that help the plant in climbing up against some support. In Lathyrus, the entire leaf is modified into a tendril In Smilax, the stipules become modified into tendrils.
2. Leaf Hooks: The leaves are modified into hooks and help the plant to climb the support. In Bignonia unguiscati, the three-terminal leaflets of the compound leave become stiff, curved to form claw-like hooks.
3. Leaf Spines: In some plants, the whole leaf or its part get modified to a hard pointed structure called the spine. This modification helps the plant to cut down transpiration and also protects the plants against the attacks of grazing animals. Any part of the leaf may get modified into the spine, e.g. Zizyphus
4. Phyllode: The lamina of the leaf falls off and its petiole gets flattened and takes on the function and shape of the leaf. This modified petiole is called phyllode. There are about 300 species of Australian Acacia, all showing the phyllode.
5. Leaf Pitcher. In the pitcher plant, the leaf becomes modified into a pitcher. There is a slender stalk that coils like a tendril holding the pitcher vertical and the basal portion is flattened like a leaf. The insects are attracted by these structures and fall into the pitcher to be killed and digested by the plant with the secretion of the hydrolytic enzymes. This type of modification is found in insectivorous plants, e.g., Nephenthes.
6. Leaf Bladder: Some of the leaf segments are modified to form the bladder. These bladders serve as floats for the aquatic plants and for trapping the insects e.g.Utricularia.
B. STEM
Theory: The upright part of the plant which grows from the plumule of seed is called the stem. The stem bears nodes leaves and branches. The stem, its branches, leaves, flowers and fruits constitute the stem shoot system of the plant. Some stems are modified to perform various functions
Modification of Stem:
Stems are variously modified into underground, subaerial and aerial stems for performing functions like manufacturing and storing food, perennation (overcoming unfavourable climatic conditions), providing mechanical support and protection and propagating vegetatively.
A. UNDERGROUND STEMS: The four different types of the underground stem are.
a. Rhizome Rhizomes are horizontal, thick, stout underground stems. They are swollen with the storage of food materials. They have nodes and internodes. These perennial structures bear axillary buds. The branching of the stem may be racemose (e.g. Saccharum) or Cymose (eg. Ginger).
b. Corm: Fleshy, spherical stem with flattened base, grows vertically, bears many scale leaves, distinct nodes and internodes, buds and adventitious roots.
Examples: Saffron, Yam, Gladiolus, Colocasia
c. Bulb: Reduced, flattened discoid stem with crowded nodes bearing overlapping fleshy (inner) and dry (outer) scale leaves. A cluster of adventitious roots arises from the base of the bulb. Bulbs are of two following types:
i. Scaly bulb: It is without any tunic, eg, Lily.
ii. Tunicated bulb: It is covered by a sheath of dry membranous scale leaves called a tunic, eg. onion and garlic
d. Tuber: Swollen tips of underground lateral branches of stem store food as starch, bear eyes. Each eye is a node that bears bud and scar of scale leaves. Example: Potato.
B. SUBAERIAL STEM
Stems are weak, therefore lie prostrate on the ground or may get partially buried in the ground.
a. Runner It has long and thin internodes and the branches creep over the surface of the soil. They develop adventitious roots from the lower sides of the nodes. Example Grass, Oxalis.
b. Stolon Weak lateral branch which grows upwards then arches down to meet the soil, strike roots and produce daughter plants. Examples: Mint, Jasmin
c. Offset: It is a short runner with one internode long It originates from the leaf axil, grows as a short horizontal branch. It is generally found in aquatic plants like Eichornia (water hyacinth), Pistia (water lettuce), Houseleek.
d. Sucker: Underground runner which grows horizontally for a distance under soil then emerges obliquely upwards, daughter plants. Example: Chrysanthemum
C. AERIAL STEMS
In certain plants, the aerial stem or buds get modified to perform special functions like climbing, protection, food storage, vegetative propagation etc.
a. Stem tendrils: Stem or its branches get modified into threadlike, spirally coiled, leafless structures (tendrils) that twine around neighbouring objects and help weak plants to climb. Example: Grapevine.
b. Thorns. Straight, pointed, hard structures: modifications of axillary (Citrus) or terminal (Carissa) bud; act as defence organs or as climbing organs. Examples: Carissa, Citrus, Duranta
c. Phylloclade: These are fleshy, green flattened or cylindrical branches of unlimited growth. They take part in photosynthesis and store water. Found in plants growing in dry regions. Example: Opuntia
d. Cladode: It is a phylloclade with limited growth, ie, with only one or two internodes; help in photosynthesis. Example: Asparagus Ruscus.
e. Bulbil: These are modified vegetative or floral buds with stored food and are meant for vegetative propagation. Example: Dioscorea.
C. ROOT
Theory: The plant body consists of root and shoot systems. Different parts of the plant perform different functions. The root is the underground cylindrical part of the plant which develops from the radicle and grows vertically downwards into the soil. Root fixes the plant in the soil. It absorbs water and minerals from the soil. Roots are modified into different forms to perform specific functions other than their normal functions. Modification in roots is found in both the tap root systems and adventitious root systems.
A. Tap Root Modifications
Taproots are modified into different structures, these modified structures carry out specific functions like food storage. There are different types of modified tap roots like Fusiform, Napiform, Conical, Tuberous or tubercular roots, pneumatophores.
- Fusiform: The root is swollen in the middle and tapers towards the base and the apex e.g. Radish.
- Napiform: The root tuber has a top-like appearance. It is very broad at the base and suddenly tapers into a tail at the apex eg. Beetroot, Turnip.
- Conical: In the conical form of root modification the roots are swollen and are broad at the base, the apex part gradually tapers forming a cone like structure. Example carrot.
- Tuberous: In the case of tuberous roots, the roots are thick and fleshy. They do not form any definite shape. Example: Mirabilis jalapa.
- Pneumatophores (Breathing Roots): In mangrove plants (e.g Avicennia), which grow in marshy areas, produce branches that come out of soil or mud for respiration or breathing. They have small pores or pneumothodes (lenticels) for this purpose.
B. ADVENTITIOUS ROOT SYSTEM
1. For Storage of Food: In some plants, the adventitious roots store food and become fleshy and swollen. It may assume the following shapes.
a. Tuberous Roots: These are without any definite shape. Eg: Sweet Potato
b. Fasciculated Root: In this type, the tuberous roots occur in clusters at the base of the stem eg. Asparagus, Dahlia.
c. Nodulose Roots: In this type, the roots become swollen near the tips. Eg. Mango, ginger and turmeric.
2. For Mechanical Support:
a. Stilt Root: These adventitious roots arise from the first few nodes of the stem. These roots grow obliquely downwards. They act like stilt and they provide mechanical support to the plant. eg. Mitize, sugarcane and pandanus.
b. Prop Root: They are not strongly anchored to the soil. Hence, these plants develop adventitious roots near the base of the stem. These roots grow vertically downwards. They act as pillars and provide mechanical support to the plant. Example banyan tree.
c. Climbing roots: This type of root system is found in climbers. Adventitious roots are developed from the nodes and are aerial roots. These aerial roots twist and clasp the support and help in climbing. Example- Betel, Pothos, etc.
3. For Vital Functions:
a. Epiphytic Roots: These are of two following types:
i. Clinging Roots: These cling to the host plant for support.
ii. Aerial Roots: These roots hang downward. Aerial roots are of green colour and have a special outer covering called velamen. This covering helps the plant in absorption of moisture from the air, Example- Vanda.
b. Photosynthetic Roots: These are green due to the development of chlorophyll in them. They are photosynthetic in function. Example: Tinospora.
c. Parasitic Roots: These roots grow into the host and come in contact with its conducting tissues. As they absorb nourishment from the plant and are therefore called sucking roots. Example- Cuscuta.
Remedial Biology Practicals
- Introduction to experiments in biology a) Study of Microscope b) Section cutting techniques c) Mounting and staining d) Permanent slide preparation 2. Study of cell and its inclusions 3. Study of Stem, Root, Leaf, seed, fruit, flower and their modifications 4. Detailed study of frog by using computer models 5. Microscopic study and identification of tissues pertinent to Stem, Root Leaf, seed, fruit and flower 6. Identification of bones 7. Determination of blood group 8. Determination of blood pressure 9. Determination of tidal volume
First Year B Pharm Notes, Syllabus, Books, PDF Subjectwise/Topicwise
First Year B Pharm Notes, Syllabus, Books, PDF Subjectwise/Topicwise
Suggested readings
Recommended readings: