Tiêu đề MORPHOLOGY OF FLOWERING PLANTS.pdf ✅

 Digital www.allendigital.in [ 3 ] 1. Introduction : • The angiosperms show large diversity in external structure or morphology • The angiosperms are characterized by presence of roots, stems, leaves, flowers and fruits • The underground part of flowering plant is the root system while the portion above the ground forms shoot system 2. The Root : Roots are (+) vely geotropic, (+) vely hydrotropic, (–) vely phototropic. (1) Types of Roots : (A) Tap Roots : In most of the dicot plants, the direct elongation of the radicle leads to the formation of primary root. It bears lateral roots of several orders that are referred to as secondary, tertiary roots, etc. The primary roots and its branches constitute the tap root system. e.g. : Mustard plant (B) Adventitious Roots : In some plants, like grass, Monstera and the banyan tree, roots develop from parts of the plant other than the radicle and are known as adventitious roots. Tertiary roots Secondary roots Primary root Tap root system Lateral roots Laterals Main root Tap root Morphology of Flowering 01 Plants Secondary root Primary root Bud Leaf Stem Fruit Flower Node Internode Root system Shoot system Parts of a Flowering Plant
NEET : Biology [ 4 ] www.allendigital.in  Digital (C) Fibrous Roots : In monocot plants, the primary root is short lived and is replaced by a large number of roots. These roots originate from the base of the stem and constitute the fibrous root system. e.g. :- Wheat plant. Functions of the root system : • Absorption of water and minerals. provide a proper anchorage to the plant parts, • storage of reserve food material (Carrot, radish, turnip, sweet potato and Asparagus) and • synthesis of PGR (plant growth regulators). (2) Modification of Root : • Roots in some plants change their shape and structure and become modified to perform functions other than absorption and conduction of water and minerals. (A) Modification of Tap Root : (i) For Food Storage : (a) Fusiform roots/Spindle shaped roots - These roots are thicker in the middle and tapering on both ends. e.g. Radish (b) Conical roots - These roots are broader at base and gradually tapper towards apex e.g. Carrot (c) Napiform roots - These roots become swollen and spherical at upper end and tapering (like a thread) at their lower end. e.g. Turnip, sugarbeet = beet root (Beta vulgaris) (d) Tuberous roots - These roots do not have regular shape and any portion of roots become swollen & fleshy. e.g. Mirabilis. (ii) For N2-Fixation : • Nodulated roots - Nodules are formed on branches of roots by nitrogen fixing bacteria (Rhizobium). e.g. Pea, gram, bean Adventitious roots Fibrous roots Conical root Fusiform root Napiform root Tuberous root Nodulated root
Morphology of Flowering Plants  Digital www.allendigital.in [ 5 ] (iii) For Respiration (Pneumatophores) : • In marshy/swampy areas, scarcity of oxygen is found. Some branches of tap root of the plants which grow in this region, grow vertically upward and comes on the surface. These roots are called pneumatophores which have minute pores called pneumathodes or lenticels by which air enters in the plant and plant gets oxygen for respiration • Pneumatophores are negatively geotropic. e.g. Rhizophora, (Mangrove plants). (B) Modification of Adventitious Roots : (i) For storage :- (a) Fasciculated roots : These are adventitious roots occurring in clusters and all of them are swollen. e.g. Asparagus, dahlia (b) Tuberous adventitious roots : The food is stored in these roots, therefore they become swollen and irregular. These roots have no definite shape e.g. Sweet potato (Ipomoea batatas) (ii) For support : (a) Stilt roots or brace roots :- These roots arise from lower node and enter in the soil. These roots are supporting roots. e.g. Maize, sugarcane. (b) Prop roots or pillar roots :- These hanging roots arise from branches of plant and grow downward towards the soil. These roots support the tree. e.g. Banyan (Ficus benghalensis) (c) Climbing roots :- These roots arise from nodes and help in climbing. e.g. Money plant (Pothos), Monstera, betel (Piper betel), black pepper. Modification of Adventitious roots For Storage For Support For special function Fasciculated roots Asparagus Sweet potato Pneumathodes Pneumatophore (Negatively geotropic) Normal root Pneumatophores in Rhizophora
NEET : Biology [ 6 ] www.allendigital.in  Digital (iii) For Special Function :- (a) Foliar roots or Epiphyllous roots :– When roots arise from leaf then they are called foliar roots. Help in vegetative propagation e.g. Bryophyllum. (b) Sucking roots or Haustorial roots or Parasitic roots : In parasitic plants, roots enter the host plant to absorb nutrition from the host. e.g. Cuscuta. Regions of the Root : • From this region some of the epidermal cells form very fine and delicate, thread-like structures called root hairs. • The cells of the elongation zone gradually differentiate and mature. • The cells of this region are very small, thin-walled and with dense protoplasm. They divide repeatedly. • It protects the tender apex of the root as it makes its way through the soil. Stilt roots Prop roots Climbing roots Modification of root for support : Banyan tree Leaves Stilt roots Branches Prop roots (growing downward) Petiole Support Stem Climbing roots Adventitious Buds Foliar roots Parasitic roots Root cap Region of meristematic activity Region of elongation Region of maturation