Morphology of Flowering Plants

Root


  • It is positively geotropic [only main root] and hydrotropic and frequently it shows negative phototropism without nodes, inter nodes, leaves, buds, flowers and fruits.
  • Root cap (or) calyptra is a cap like covering over the root tip for protection against friction from soil particles.
  • Root cap is absent is epiphytes, parasites, hydrophytes and mycorrhizal roots.
  • The growing point is meristematic zone, where the cells are thin and non - vacuolated. Which could be otherwise called as zone of cell division / Mycorrhizal formation.
  • Behind the tip is the zone of elongation, where the cells elongate rapidly
  • Phloem and Xylem differentiate at root hair zone which is absent is parasitic and mycorrhizal roots.
  • Bulk of the root is made of zone of maturation is root.
  • A complex of one type of roots and their branches is called root system which is of 2 types - (i) Tap root system (ii) Adventitious root system.
  • Tap root is a primary root which develops elongation of radicle and persist through out the life of the plant.
  • Tap root bears secondary roots is an acropetal succession which also bear tertiary roots. Final root branches are called root lets which bears root caps and root hairs.
  • Tap root system is of 2 types (i) Deep feeder eg : Mango, Peepal (ii) Surface feeder eg : solanum, nigrum
  • To perform some secondary functions, roots undergo modifications
  • Fleshy / Storage top roots.
    (i) Conical - Carrot
    (ii) Fusiform - Radish
    (iii) Napiform - Turnip
    (iv) Tuberous - Mirabilis
  • In legumes, the roots bear numerous irregular swellings called nodules (or) Tubercles
  • Respiratory roots (or) Pneum atophores are short, vertical and negatively geotropical roots which occur in mangrove plants, where the upper ends bear lenticels (or) Pneumathodes for exchange of gases.
  • Adventitious root are common in pteridophytes and monocot and are not deep rooted. Eg : Fibrous roots : Grass, wheat.
  • Fleshy adventitious roots :
    (i) root tubers : Sweet potato, Tapioca
    (ii) Fasciculated roots : Asparagus, Dahlia
    (iii) Palmate : Orchis
    (iv) Moniliform / beaded : Eg : Bitter gourd, portulaca
    (v) Nodulose roots : Curcuma amada
  • Pillar / prop / Columnar roots : Eg : Banyan tree
  • Still roots : Sugarcane, Maize, Sorghum.
  • Haustorial / Parasitic / sucking roots : Eg : Cuscata, Viscum
  • Clinging / Climbing roots. Betel, Black pepper, Money plant, Ivy.
  • Photosynthetic / assimilatory roots : Tinospora, podostemon, Trapa.
  • Hygroscopic roots : Vanda, dendrobium.
  • Epiphylbus roots : Begonia, Bryophyllum

View the topic in the video from the time 0:51 to 16:35

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