morphology of plants

• the primary roots and its branches constitute the tap root system in DICOTS
• in monocots, primary roots is short living and are replaced by a no.of roots which originate from the base of the stem and constitute the fibrous root.
• tap root system present in dicots and fibrous root present in monocots
• in some plants like grass, monstera and banyan tree, roots arise from the parts of the plants other than the radicle and are called adventitious roots.
• functions are root are anchorage, absorption of water and minerals, storing reserve food and synthesis of plant growth regulators.
• regions of the root

  • root cap
  • region of meristematic activity
  • region of elongation
  • region of maturation
• the root at the tip is covered by root cap which protects the root
• part above the root cap is known as region of meristematic activity. cells are thin, small with dense cytoplasm and divide repeatedly
• part above the region of meristematic activity is known as the region of elongation. cells undergo rapid elongation and enlargement and is responsible for the growth of root in length.
• region of maturation lies proximal to the region on elongation. some cells undergo maturation. some of the epidermal cells form very delicate thin fine root hairs
• root modification-

  storage

  support

  breathing
• roots(storage)

  roots of carrots, radish, sweet potato
• roots(support)

  roots of banyan tree called prop roots and silt roots of maize and sugarcae
• Prop roots develop from the upper part of the stem, especially the horizontal branches while stilt roots develop from the basal nodes of the main stem. Prop roots pass down into the soil in a vertical position while stilt roots develop obliquely at an angle to the stem.
• roots (Breathing )

  Rhizophora in swampy areas have pneumatophores growing up from the ground for breathing.
• Stem bears branches,leaves flowers,fruits, nodes and internodes.
• Nodes - The regions of the stem where leaves are born 

  Internodes - the region between nodes

  Stem has buds axially or terminally.

  Stems help in conduction, storage, photosynthesis ,propagation
• Stems of potato ,ginger,turmeric ,Zaminkand,Colocasia store food
• Stem acts as  organ of perennation that helps to tide over unfavourable conditions.
• Axillary  buds form  coiled tendrils that help plants to climb.eg;Grapevines,bitter gourd.

  Axillary buds form thorns .eg: Citrus,Bougainvilia 
• Stem may also gets flattened to perform photosynthesis. eg;Opuntia 

  Stem is fleshy ,cylindrical in Euphorbia.
• underground stems of grass,Strawberry etc spread underground and when the older parts die ,new parts are formed from the existing ones.
• In Mint,Jasmine,The lateral branches arch downwards to touch the ground

   Pistia, Eichhornia etc have a rosette of leaves and tuft of roots at nodes .
• In Banana,Pineapple and Chrysanthemum, the lateral branches originate from underground portions  grow horizontally beneath soil ,then come out obliquely upward giving rise to leafy shoots.
• perennation - the ability of plants, to survive from one season to another, especially under unfavourable conditions such as drought or winter. It involves development of a perennating organ, which stores enough nutrients to sustain the organism during the unfavourable season, and develops into one or more new plants the following year. Common forms of perennating organs are storage organs (e.g. tubers ,rhizomes and corm)
• • The leaf develops at the node and bears a bud at its axil [axillary bud] that forms branches later
• • Leaf originates from shoot apical meristem.
• The leaf has 3 parts - leaf base,lamina,Petiole.
• The green expanded part with veins and veinlets is called lamina or leaf blade. The middle prominent vein is called midrib. Veins and veinlets help in conduction.
• The leaf is attached to stem by leaf base and may bear small leaf like structures called stipules. stipules protects axillary buds.
• • In monocots the leaf base expands to form a sheath that covers the stem partially or wholly.
• In leguminous plants ,the leaf base become swollen to form pulvinus
• Petiole is a slender stem that support leaf blade. Petiole allows leaf blades to flutter in wind that will cool off leaf blade and brings fresh air.
• The arrangement of veins and veinlets  

  in leaf lamina is called venation.
• reticulate venation - veins are arranged as a network or web like structures. typically in dicotyledonous plant. eg- mango , hibiscus etc
• parallel venation - veins run parallel to one another along with the leaf from base to tip . mostly in monocotyledonous. eg- wheat, maize, grass etc
• types of leafs - simple and compound.

  compound is divided into pinnately compound leaf and palmately compound leaf
•  A leaf having a single or undivided lamina is called simple leaf. eg. Hibiscus,Guava
• Compound leaf: the leaf blade is clearly divided into many distinct parts called leaflets.
• 1. Pinnately compound leaves: A number of leaflets are arranged on a common axis,the rachis[midrib].
  2. Palmately compound leaves - The leaflets are attached at a common point [at the tip of petiole] eg. silk cotton