Plant Morphology Lecture 11 PDF

Morphology of flowering plants 1. Root 2. Stem 3. Leaf 4. Flower 5. Fruit 6. Seed Morphology of Root Characteristics : 1. Root is defined as the descending part of the plant axis. 2. It is positively geotropic. 3. It is positively hydrotropic 4. It is negat...

Morphology of flowering plants 1. Root 2. Stem 3. Leaf 4. Flower 5. Fruit 6. Seed Morphology of Root Characteristics : 1. Root is defined as the descending part of the plant axis. 2. It is positively geotropic. 3. It is positively hydrotropic 4. It is negatively phototropic. 5. It develops from the radicle of the embryo during seed germination. 6. Non green and cylindrical. 7. Produce only similar organs i.e. secondary and tertiary roots 8. They do not show nodes and internodes  Morphology of Root 1. Region of root cap: - The tender apex of the root is protected with a multicellular cap like structure called root cap. - The cells of the root cap secrete mucilage for lubricating the passage of root through the soil. 2. Region of cell division or meristematic region: - It is a small region about 1mm in length. - This is the growing part of the root and is protected by the root cap. - It is made up of thin walled, compactly arranged meristematic cells which have the power of division. - This region helps in longitudinal growth by the addition of new cells 3. Region of elongation: - It lies just above the meristematic region. - The cells of this region are newly formed and they elongate rapidly. This increases the length of the root. - The cells of this region help in the absorption of mineral salts  Morphology of Root 4. Region of root hair or root absorption: - Surface of this area is covered with numerous root hairs. - The cells of the outer layer known as piliferous layer or epiblema produce root hair. - The root hairs are elongated, single celled, tubular structures which remain in contact with soil particles. - The root hairs increase the surface area of absorption. - They are short lived and are replaced by new root hairs after every 10 to 15 days and is responsible for absorption of water. 5. Region of maturation or cell differentiation: - It forms the major part of the root. - The outermost layer of this region has thick walled impermeable cells. - The enlarged cells undergo differentiation to form different types of primary root tissue like cortex, endodermis, xylem, phloem, etc. This region helps in fixation of plant body into the soil and also in conduction of absorbed substances. - Lateral roots also develop from this region of the root.  Morphology of Root FUNCTIONS OF THE ROOT: PRIMARY : - The normal functions of the roots are fixation or anchorage of the plant body into the soil (substratum), absorption of water and minerals from the soil and conduction of absorbed materials up to the base of the stem. SECONDARY : - In some plants roots perform certain special functions and such roots undergo necessary modifications. Some roots become fleshy or swollen for the storage of food materials e.g. carrot, radish, asparagus, sweet potato, Dahlia, etc. - After becoming green some roots manufacture food by photosynthesis e.g. Tinospora, Trapa, Orchids etc. - Some roots help in exchange of gases (respiration) - Aerial roots absorb moisture from the air e.g. Orchids. Thus modified roots perform different functions.  Morphology of Root TAP ROOTS OR TRUE ROOTS: - develops from the radicle of an embryo during seed germination is called a true root or tap root. - The main root is called primary root. - Its branches of first order are called secondary roots and branches of secondary order are called tertiary roots and so on. - The main root along with its branches forms a tap root system - Presence of a tap root system is a characteristic feature of dicotyledonous plants. The tap root normally grows vertically downwards to a lesser or greater depth, while secondary and tertiary roots grow obliquely downwards or some grow horizontally outwards.  Morphology of Root ADVENTITIOUS ROOT SYSTEM: - A root that develops from any other part other than the radicle is known as adventitious root. - Such roots may develop from the base of the stem, nodes or from leaves. - In monocots, radicle is short lived and from the base of the stem a thick cluster of all equal sized roots arises. This is known as the adventitious root system e.g. Maize, wheat, sugarcane, etc. - It is also known as fibrous root system as the adventitious roots of grasses (monocots) look like fibres. - Fibrous roots do not grow very deep into the soil  Morphology of Root Modifications Tap Adventitious 1. Storage of food 1. Storage of food 2. Respiration 2. Support 3. Special functions  Morphology of Root MODIFICATIONS OF TAP ROOT : 1. Storage of food - The tap root (primary) becomes fleshy and swollen due to the stored food. - The secondary roots remain thin. - Hypocotyl (embryonic region between cotyledons and radicle) may also join the tap in storing food. - Stem is reduced and discoid in the beginning and bears radical leaves. - The swollen tap root acquires some typical shape and is accordingly classified into the following three types :  Morphology of Root MODIFICATIONS OF TAP ROOT : 1. Storage of food FUSIFORM ROOT : e.g. radish (Raphanussativus). CONICAL ROOT : e.g. carrot (Daucus carota). NAPIFORM ROOT : e.g. beet (Beta vulgaris).  Morphology of Stem CHARACTERISTICS : - The aerial part of the plant body is collectively described as shoot system. - Main axis of this shoot system is called the stem. - Stem can be defined as the ascending part of the plant axis, which develops from the plumule, - It is usually negatively hydrotropic, negatively geotropic and positively phototropic. - It bears a terminal bud and axillary buds in the axils of leaves, for growth. - It is differentiated into nodes and internodes. - At the nodes, it produces dissimilar organs such as leaves and flowers and similar organs such as branches, exogenously i.e. originate from outer tissue. - The young stem is green and is capable of performing photosynthesis.  Morphology of Stem BUDS Vegetative Floral The buds which develop into The buds which develop into branches are called vegetative buds Flowers are called floral buds. - Apical buds : located at the apex of stem - Axillary buds : located in the axils of leaves - Accessory buds : located on the sides or above the axillary buds  Morphology of Stem FUNCTIONS OF STEM: - The primary functions of stem are to produce and support lateral appendages such as branches, leaves, flowers and fruits, conduction of water and minerals to different parts of shoots and transport food to all plant parts. - Stem may, however, get modified to perform additional or functions such as - storage of food and water, - proliferation and propagation, - procuring support for climbing, - synthesis of food (photosynthesis).  Morphology of Stem MODIFICATIONS OF STEM Underground Sub-aerial Aerial 1. Rhizome 1. Runner 1. Tendril 2. Tuber 2. Stolon 2. Thorn 3. Corm 3. Offset 3. Phylloclade 4. Bulb 4. Sucker 4. Cladode 5. Bulbil  Morphology of Stem UNDERGROUND MODIFICATIONS RHIZOME: - Growth of rhizome takes place horizontally with the help of the lateral bud -.They produce adventitious roots  Morphology of Stem UNDERGROUND MODIFICATIONS TUBER : - Tubers are actually the swollen ends or tips of special swollen underground branches, due to the storage of food (carbohydrate like starch). - The tubers show nodes and internodes bear scale leaves with axillary buds, commonly called as eyes. - Under favorable conditions these eyes sprout and produce aerial shoots. - Thus tubers helps in vegetative propagation. Tubers do not produce adventitious roots, thus they differ from rhizomes e.g. potato (Solanum tuberosum)  Morphology of Stem UNDERGROUND MODIFICATIONS BULB : - It is a condensed; disc like underground stem, which itself does not store food material. - The upper surface of disc like stem is slightly conical and bears centrally placed apical bud and many concentrically arranged overlapping scale leaves. - Inner scale leaves or leaf bases store food and are thick and fleshy, while outer few scaly leaves remain thin and dry and are protective in function. - Lower surface of disc-like stem produces adventitious roots.  Morphology of Stem UNDERGROUND MODIFICATIONS BULB : - The discoid stem with compactly arranged fleshy leaves above and fibrous roots below is commonly called bulb. It is almost spherical. - When the fleshy scale leaves surround the apical bud in the form of concentric rings, it is called tunicated bulb e.g. onion. - Sometimes they may partially overlap each other by their margins only, such bulbs are called scaly bulbs e.g. garlic.  Morphology of Leaf A dorsi-ventrally compressed, lateral appendage of stem produced at the nodes and is specialized to perform photosynthesis CHARACTERISTICS OF LEAF: - Leaf is a thin, expanded, green structure. - The green colour of the leaf is due to the presence of chlorophyll pigment. - It is exogenous in origin. - It is borne on the stem at the node. - An axillary bud is often present in the axil of each leaf. - It has limited growth. - It does not possess apical bud or a regular growing point.  Morphology of Leaf PARTS OF A TYPICAL LEAF : PULVINUS LEAF BASE: - The part of leaf attached to the stem or branch is known as leaf base. - In monocots, the leaf base expands into a sheath covering the stem partially or completely. - Leaves of some plants possess a pair of lateral outgrowths at the base, on either sides of axillary bud. These outgrowths are called stipules and such leaves are called stipulate leaves. - The leaves without stipules are called ex- stipulate leaves. Stipules are usually green. - The main functions of stipules are to protect the bud and carry out photosynthesis. SHEATH STIPULES  Morphology of Leaf PARTS OF A TYPICAL LEAF : PETIOLE : - Petiole is the part of leaf connecting the lamina (L. blade) with the branch or stem. - Leaves that possess petiole are called petiolate and leaves without petiole are called non-petiolate or sessile leaves. - Function of petiole is to raise the lamina to expose it to more light and air and to help in conduction.  Morphology of Leaf PARTS OF A TYPICAL LEAF : Lamina or L. blade: - This is the largest, most important, green and flattened part of the leaf. - It plays a vital role in photosynthesis, gaseous exchange and transpiration. - The leaf is known as dorsiventral when its ventral surface is structurally different from dorsal surface, e.g. dicotyledonous leaves. - The leaves having both similar surfaces are called isobilateral. Such leaves are found in monocot plants  Morphology of Leaf LEAF VENATION : - The arrangement of veins and veinlets in the lamina is known as venation. - The veins are in fact conducting strands of lamina. - They are concerned with the conduction of water, mineral salts and food and form the structural framework of the lamina. RETICULATE PARALLEL  Morphology of Leaf RETICULATE VENATION: - When the veins and veinlets form a network, it is called reticulate venation. - Here the midrib is centrally placed and veins and veinlets remain distributed laterally. - It is found in dicotyledonous plants.  Morphology of Leaf PARALLEL VENATION: - In this type of venation, veins in lamina run almost parallel to one another. - It is found commonly in monocotyledonous plants.  Morphology of Leaf According to Leaf blade, the Leaf may be simple or comp SIMPLE LEAF : - Simple leaves are those in which single leaf blade or lamina is present, - e.g., Mango, Peepal, Papaya, etc. COMPOUND LEAF : - Compound leaves are those in which the leaf blade or lamina is divided into number of segments known as leaflets or pinnae. - The leaflets never bear axillary buds in their axil.  Morphology of Leaf COMPOUND LEAF : a) Pinnately compound leaves: - In this type the leaflets are present laterally on a common axis called rachis, which represents the midrib of the leaf - (e.g. Gold mohur, Cassia)  Morphology of Leaf COMPOUND LEAF : b) Palmately compound leaves: - All the leaflets of the palmately compound leaves are attached at a common point, i.e. at the tip of petiole, like fingers of the palm.  Morphology of Leaf Arrangement of the leaf on the stem ALTERNATE - In this type, single leaf arises at each node. - The leaves arise laterally on the stem or branches, - e.g., Sunflower, Mango, China rose, Mustard etc. OPPOSITE In this type, two leaves arise from each node in opposite direction. It is of two types: WHORLED In this type more than two leaves arise from each node andform a whorl around it. - e.g., Nerium, Alstonia  Morphology of Leaf MODIFICATIONS OF LEAVES: LEAF SPINES: - In some xerophytic plants like Opuntia, the entire leaf gets modified into a small, stiff, pointed structure called spine to decrease transpiration. l