Tiêu đề Med-RM_Bot_SP-1_Ch-5_Morphology of Flowering Plants.pdf ✅

Aakash Educational Services Limited - Regd. Office : Aakash Tower, 8, Pusa Road, New Delhi-110005 Ph. 011-47623456 Chapter Contents Morphology deals with the study of forms and features of different plant organs like roots, stem, leaves, flowers, seeds, fruits etc. Morphology plays a key role in the classification of angiosperms. Fig. : Parts of a Flowering Plant THE ROOT Roots are cylindrical, underground and non-green part develop from radicle. They lack nodes, leaves, buds but give rise to endogenous lateral branches. Exceptions- Roots of sweet potato & Dalbergia bear buds. Roots move in the direction of gravity (positive geotropism) and against the direction of light (negative phototropism). The main root and its lateral branches form the root system. There are three types of root system. Chapter 5 The Root The Stem The Leaf The Inflorescence The Flower The Fruit The Seed Semi-Technical Description of a Typical Flowering Plant Description of Some Important Families Morphology of Flowering Plants
148 Morphology of Flowering Plants NEET Aakash Educational Services Limited - Regd. Office : Aakash Tower, 8, Pusa Road, New Delhi-110005 Ph.011-47623456 (i) Tap root system : The primary root is directly elongated from the radicle and grows inside the soil (e.g. dicots). 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. Main root Lateral roots (ii) Fibrous root system : In monocotyledonous plants, the primary root is short-lived and is generally replaced by a number of fine fibrous roots. These roots originate from base of the stem and constitute the fibrous root system as seen in wheat plant. Fibrous root (iii) Adventitious root system: Some plants have specialised roots called adventitious roots. These roots develop from any parts of the plant other than the radicle e.g., Grass, Monstera, Banyan tree. Main Functions of Root I. Absorption of water and minerals from the soil. II. Provide anchorage to the plant parts.
NEET Morphology of Flowering Plants 149 Aakash Educational Services Limited - Regd. Office : Aakash Tower, 8, Pusa Road, New Delhi-110005 Ph.011-47623456 III. Storage of reserve food material. IV. Synthesis of plant growth regulators. Regions of the Root (i) Root cap : The apex of the root is covered by a thimble-like, structure called root cap. It is multicellular and is made up of parenchymatous cells. It protects the tender apex of the root. (ii) Region of meristematic activity : This layer is few millimetre above the root cap (sub-apical). The cells of this layer divide repeatedly to produce new cells. (iii) Region of elongation : The cells proximal to the meristematic region undergo rapid elongation and enlargement and are responsible for the growth of roots in length. (iv) Region of maturation : The cells elongation zone gradually differentiate and mature. Hence, this zone proximal to region of elongation, is called the region of maturation. Some epidermal cells from the region of maturation form very fine and delicate thread-like structures called root hair. The root hair increases the surface area for absorption of water and minerals from the soil. Fig. : The regions of the root-tip Modifications of Root Roots in some plants undergo modifications in their shape and structure in order to perform functions like respiration, storage and protection. (i) Storage roots/ Fleshy roots : The primary tap root is modified due to storage of food and assumes various shapes. e.g., tap root of carrot, turnip, radish, beet and adventitious roots of sweet potato get swollen and store food. Turnip Carrot Sweet potato Fig. : Modification of root for storage
150 Morphology of Flowering Plants NEET Aakash Educational Services Limited - Regd. Office : Aakash Tower, 8, Pusa Road, New Delhi-110005 Ph.011-47623456 (ii) Respiratory roots : In some plants such as Rhizophora growing in swampy areas, many roots come out of the ground vertically upwards to get oxygen for respiration. Such roots are called pneumatophores. Mangrove tree Pneumatophores Lenticels (Pneumatothodes) Pneumatophore Horizontal root Absorbing roots A B Fig. : Pneumatophores or respiratory roots : A - Mangrove tree with pneumatophores, B - Pneumatophores with lenticels (iii) Prop roots : They arise from the branches of stem for providing mechanical support to heavy branches, as pillars e.g., banyan tree. Aerial roots Trunk Prop root Stem branch Fig. : Prop or pillar roots of Ficus benghalensis (banyan tree) (iv) Stilt roots : They arise from lower nodes of stem to support main axis and enter the soil obliquely e.g., sugarcane, maize.