Roots and Stems PDF

The expression “Morphology” is derived from two Latin words (Morphe = form + logos = study)  Plant Morphology It is science dealing with studying the morphological form of the plant It deals with the study of forms and features of different plant organs like roots, stems, leaves, flowe...

The expression “Morphology” is derived from two Latin words (Morphe = form + logos = study)  Plant Morphology It is science dealing with studying the morphological form of the plant It deals with the study of forms and features of different plant organs like roots, stems, leaves, flowers, seeds, fruits,…. etc.  Entire plant body The body of a typical angiospermic plant (shape 1) is differentiated into:  An underground root system  An aerial shoot system.  The shoot system consists of stem (including branches), leaves, flowers and fruits.  The roots, stems and leaves are vegetative parts, while flowers constitute the reproductive part. Seed Epigeal Seed Germination Hypogeal Seed Germination Root system  FUNCTIONS OF ROOT  Roots support the plant by keeping it fixed firmly in the soil.  Absorption of water and minerals  Storage of food  Conduction of water  Photosynthesis and respiration  Climbing  Roots hold the soil particles together Types of Roots 1 Tap roots 2 Adventitious roots plumule  Types of Roots 1) Tap roots : It develops from radicle of the germinating seed and made up of one main branch and other sub branches. present in dicotyledonous plants. A-Normal tap root B- storage tap root Normal tap root  Storage tap root 1-Conical form root 2-Fusiform root 3- Napiform root  Conical form root These roots are thicker at their upper side and tapering at basal end. eg. Carrot. eg. Carrot Conical Storage tap root  Fusiform root These roots are thicker in the middle and tappered on both ends. This type of roots helps in storage of food. eg. Radish. eg. Radish  Napiform root Napiform roots: These roots become swollen and spherical at upper end and tappered like a thread at their lower end. eg. Turnip (Brassica rapa), Sugarbeet eg. Turnip Conical Fusiform Napiform 2) Adventitious roots: originate from any part of the plant body other than the radicle. It is mostly seen in monocotyledonous plants. A- Fibrous roots B- Prop roots C- Storage (tuberous) roots D- Climbing roots E- Aerial roots F- Respiratory roots G- Haustorial or parasitic roots H- Contractile roots Fibrous roots small, thin roots  Prop roots root arises from the nodes of the stem near the soil. assist in supporting the plant in the soil. e.g. Maize  These roots store up food When food is stored in these roots, they become swollen Storage (tuberous) root  Aerial roots either pass for some distance through the air before reaching the soil or remain hanging in the air. Halophyte or mangrove grows in oxygen deficient marshy area. Some roots in these plants grow vertically & come out from soil through which air entered inside the plant. eg. Avicennia Respiratory roots  Climbing roots These roots arise from nodes and help the plant in climbing Haustorial roots They shrink 60 – 70% of the original length and bring underground organ at proper depth in the soil  Axillary (lateral) buds located in axil of a leaf Terminal & Lateral Buds Winter Buds Winter buds brown scales cover and protect embryonic parts. Present in deciduous plants (Vitis). Winter buds opened in late winter  Stems Erect Weak These are strong stems that holding itself stand, having a vertical or upright habit. Erect Stem Woody Stem Herbaceous Stems These are thin and cannot stand erect and need mechanical support to expose their leaves to the sun. The weak stem of these plants have the habit of twining around supports without any special organs for attachment (Convolvulus) Runners Branching of stems 1- Apical (dichotomous) branching Dichotomous branching 2- Axillary (Lateral) branching  Monopodial branching Indefinite branching occurs when the terminal bud continues to grow as a central leader shoot and the lateral branches remain subordinate. Casuarina equisetifolia  Sympodial branching Definite branching occurs when the apical bud is differentiated into a flower or a tendril and thus lost its ability to grow. Vitis