Plant Physiology and Development - Roots PDF

PHARM 111|PHARMACEUTICAL BOTANY WITH TAXONOMY III. PLANT PHYSIOLOGY AND DEVELOPMENT A. ROOTS I. FUNCTIONS II. TYPES OF ROOT SYSTEMS III. TYPES OF ROOTS IV. EXTERNAL STRUCTURE V. INTERNAL STRUCTURE VI. PHYSIOLOGY OF ROOT ABSORPTION VII. OTHER ROOT TYPES AND MODIFICATIONS ROOTS - imp...

PHARM 111|PHARMACEUTICAL BOTANY WITH TAXONOMY III. PLANT PHYSIOLOGY AND DEVELOPMENT A. ROOTS I. FUNCTIONS II. TYPES OF ROOT SYSTEMS III. TYPES OF ROOTS IV. EXTERNAL STRUCTURE V. INTERNAL STRUCTURE VI. PHYSIOLOGY OF ROOT ABSORPTION VII. OTHER ROOT TYPES AND MODIFICATIONS ROOTS - important underground part of all vascular plants. - the beginning of the vascular system pipeline that moves water and minerals from the soil up through the plant body. - not all plants have their roots underground - some plants have their roots growing above the ground - initiated in the embryo as the radicle. - It penetrates into the soil and forms branches. - Root makes the base of a plant which helps a plant to survive. Characteristics of Roots: Non-green Absence of leaves and buds; Positively geotropic Positively hydrotropic Negatively phototropic I. FUNCTIONS: ✓ Anchorage - ✓ Support - ✓ Absorption - ✓ Symbiotic interaction with other organisms - can form a symbiotic relationship with Rhizobia bacteria. → nitrogen fixation, which allows for the conversion of nitrogen from the atmosphere into nitrogen compounds that the plant can use to produce proteins and other building-block molecules. For nitrogen fixation to occur, rhizobia require a plant host; they cannot independently fix nitrogen. JSBW’24 1  PHARM 111|PHARMACEUTICAL BOTANY WITH TAXONOMY III. PLANT PHYSIOLOGY AND DEVELOPMENT - Roots also develop associations with Mycorrhizal fungi. → Mycorrhizae are fungi that grow in association with roots of a wide range of plants. ✓ Nutrient storage - Roots of some plants can swell and store high-energy compounds like starch and sugar. Roots also store some protein and other nutrients, but the focus is typically on high-energy carbohydrates. II. TYPES OF ROOT SYSTEMS 1. TAP ROOT SYSTEM - develops from the radicle and continues as the primary root (tap root) which gives off lateral roots. - provides strong leverage and anchorage in the soil. 2. FIBROUS ROOT SYSTEM - the primary root is short-lived. - A cluster of slender, fiber-like roots arises from the base of the radicle and plumule which constitute the fibrous root system. - main root system of monocots. III. TYPES OF ROOTS 1. Tap root – It is the primary and the main root that develops from the radicle, bears numerous branches and remains underground. 2. Adventitious root – These are roots that develop from any part of the plant except the radicle. They may be aerial or underground. They may grow from node (money plant, bamboo), stem cutting (rose), tree branch (banyan) or stem base (fibrous roots in monocots). IV. EXTERNAL STRUCTURES (Regions of Roots) 1. Root Cap Region - **Dictyosomes - secretes mucigel **Amyloplasts – contains starch ** Pandanas are a plant that contains multiple root caps. 2. Meristematic Region - Meristematic cells are found just a few mm over the root cap - cells are thin-walled with dense protoplasm - cells divide actively. a. Apical Initials – group of cells known as - Growing point → consist of group of actively dividing cells, make up the primary meristem - Primary meristem → consists of cells that have begun to show differentiation - The three meristematic areas are: - Protoderm - Ground Meristem - Procambium JSBW’24 2  PHARM 111|PHARMACEUTICAL BOTANY WITH TAXONOMY III. PLANT PHYSIOLOGY AND DEVELOPMENT 3. Region of Elongation - Enlargement of cells, allowing roots to grow lengthwise (Length can be nearly 4-8 mm) - It lies next to the meristematic region. - cells are mature nad make up the embryonic tissue/generative tissue → Dermatogen - outermost layer → Periblem - Inner to dermatogen → Plerome - central region 4. Region of Maturation - the cells differentiate into various tissues - Embryonic tissues undergo modification and maturation →Dermatogen → Its cells mature and make up the → Periblem → Its cells mature into the → Plerome → Its cells mature into                   V. INTERNAL STRUCTURES 1. Epidermis - one-cell thick and it covers the root except the root cap 2. Cortex - formed by the ground meristem and occupies the largest cross-section area of the root a. Hypodermis b. Parenchyma cells c. Endodermis 3. Stele - central part of the root a. Pericycle b. Vascular tissues c. Parenchymatous pith JSBW’24 3  PHARM 111|PHARMACEUTICAL BOTANY WITH TAXONOMY III. PLANT PHYSIOLOGY AND DEVELOPMENT VI. PHYSIOLOGY OF ROOT ABSORPTION 1. Water – absorbed thru 2. Minerals – absorbed thru **Path of Water into the Roots 1. Apoplastic Pathway: water enters thru a set of interconnected porous cell walls which function for conduction 2. Symplastic Pathway: water and minerals enter thru interconnected cytoplasm of cells VII. ROOT MODIFICATIONS - Tap roots and adventitious roots can get modified into a variety of forms to perform various functions A. Modifications of Tap Roots 1. For Food Storage Conical roots Fusiform roots Napiform roots Tuberous roots 2. For better Respiration Nodulated Roots B. Modification of Adventitious Roots 1. For Food Storage Simple Tuberous Roots Nodulose Roots Fasciculated Tuberous Roots Moniliform Roots Annulated Roots 2. For Support Prop Roots: Stilt Roots:. Climbing Roots: JSBW’24 4  PHARM 111|PHARMACEUTICAL BOTANY WITH TAXONOMY III. PLANT PHYSIOLOGY AND DEVELOPMENT Clinging Roots: Buttress Roots: ** For Special Functions 3. For absorbing atmospheric pressure Epiphytic Roots: 4. For sucking nutrition from host Sucking Roots: 5. For buoyancy and respiration Floating Roots: 6. For photosynthesis Assimilatory Roots: 7. For vegetative propragation Mycorrhizal Roots: The symbiotic association of a fungus with higher plants is called mycorrhizal root. The fungus absorbs nutrients from the soil for the plant, and the plant, in turn, provides organic food to it. Eg., Pinus Reproductive Roots: In some plants such as sweet potato, the adventitious roots give rise to buds which develop into leafy shoots. Root cuttings are the main mode of reproduction. HUMAN RELEVANCE OF ROOTS 1. Food source 2. Spices 3. Dyes 4. Ornaments 5. Industry 6. Drugs/Medicines 7. Insecticide 8. Prevent erosion 9. Water conservation JSBW’24 5