Root morphology

1. Dendrology
(FSA-102)
Root Morphology
Dr. Swati Shedage
Assistant professor (FBTI)
CoHF, RLBCAU

2. Root
Radicle comes out/arise from the seed coat in the form of soft
structure and move toward the soil. It develops and forms primary
root.
Root, in botany, that part of a vascular plant normally underground.
Its primary functions are anchorage of the plant, absorption
of water and dissolved minerals and conduction of these to
the stem, and storage of reserve foods. The root differs from the
stem mainly by lacking leaf scars and buds, having a root cap, and
having branches that originate from internal tissue rather than from
buds.
General Characters :
• Roots are non green, underground, (+) geotropic, (–) phototropic and (+)
hydrotropic.
• Roots do not bear buds.
• Buds present for vegetative propagation in sweet potato (Ipomea) and
Indian red wood (Dalbergia)
• Roots do not bear nodes and internodes.
• Roots have unicellular root hairs.
• It remains buried in the soil
• It is white and translucent when young but become brown with the age
• It ends in tap root cap
• Nodes and internodes are absent
• It functions for absorption of water and minerals, salts, and fixation of
plants

3. • The primary root, or radicle, is the first organ to appear when a seed germinates.
• It grows downward into the soil, anchoring the seedling.
• In gymnosperms and dicotyledons (angiosperms with two seed leaves), the radicle becomes
a taproot.
• It grows downward, and secondary roots grow laterally from it to form a taproot system.
• In some plants, such as carrots and turnips, the taproot also serves as food storage.
• Grasses and other monocotyledons (angiosperms with a single seed leaf) have a fibrous root
system
• This network of roots does not arise as branches of the primary root but consists of many
branching roots that emerge from the base of the stem.

4. Roots are of two types :
✧ Tap root ✧ Adventitious root
Tap root : It develops from radicle and made up of one main branch and other sub
branches. The primary roots and its branches constitute tap root system. e.g. Dicot roots.
Adventitious roots : In some plants, after sometime of the growth of tap root which arises
from radicle, stops and then roots, develop from other part of plant, which are branched or
unbranched, fibrous or storage, are known as adventitious roots and constitute fibrous root
system. e.g. Monocot roots.

5. Morphologically four distinct regions are present in roots.
• Root cap (Calyptra): It is terminal structure. It protects tender apex of root.
• Meristematic zone : Cells of this regions are very small and thin walled. They
divide repeatedly and increase cell number. Length 1-3 mm.
• Elongation region : The cells proximal to meristematic zone undergo rapid
elongation and enlargement and are responsible for rapid growth of roots. 5-6
mm long.
• Maturation region : Cells proximal to region of elongation gradually
differentiate and mature. Root hairs are present in maturation zone.

6. Adventitious root:
1. Arial root: these roots comes out from the stem and branches of the plants e.
Banayan, Ficus pumila,Hedera helix, Tinospora.
2. Foliar roots: these roots develop from the leaf blade or from the petiole e.g
Bryophyllum and Ruscus
3. Subterranean roots: these roots develop from the collar region and grow in to the
soil. Fibrous roots in monocotyledons. Such as cluster of roots arising from the
rhizome of Bamboos and from nodes of grasses

7. Tap root modification:
1. Modified tap root for storage :
• Fusiform roots : These root are thicker in the middle and tappered on both ends. In this type root help in
storage of food. eg. Radish.
• Conical roots : These roots are thicker at their upper side and tapering at basal end. eg. Carrot, Saussurea
lappa
• Napiform : These roots become swollen and spherical at upper end and tappered like a thread at their
lower end. eg. Turnip (Brassica rapa), Sugarbeet
• Tuberous root : Such roots do not have regular shape and get swollen & fleshy at any portion of roots. eg.
Mirabilis.
• Nodulated roots: They occur in the secondary roots in the shape of small spherical structure known as
root nodule. This nodule contain nitrogen fixing bacteria which absorb free nitrogen from the atmosphere
and convert it in to nitrate which can be assimilated by the plants.

8. Modification of adventitious roots :
1. Food Storage adventitious roots
• Tuberous root : When food is stored in these roots, they become swollen and form a bunch.
E.g.Sweet potato (Ipomea batata), Dioscorea
• Fasciculated – Roots arise in bunch (cluster) from lower node of the stem and become fleshy
e.g. Dahlia, Asparagus, Ruellia tuberosa
• Beaded or moniliform : When root swells up like a bead at different places after a regular
interval. eg. Vitis, Momordica (Bitter gourd), Portulaca.
• Nodulose : In this type, tips of roots swell up. eg. Melilotus, Curcuma amoda.
• Annulated : Roots having series of ring like swellings eg. Psychrotia

9. 2. Modification for mechanical support
A. Stilt roots or brace roots : When root arises from lower nodes and enter in soil
obliquely, known as stilt roots eg. Maize, Sugarcane, Pandanus (screwpine).
B. Prop root or pillar roots : when root arises from branches of plant and grows
downward towards soil. It function as supporting stem for the plant. eg. Banyan.
C. Climbing roots – These roots arise from nodes and helps the plant in climbing. eg.
Money plant (Pothos), Betel, Black pepper, Techoma.
Stilt roots

10. 3. Modification for vital function:
A. Arial roots: These roots found in epiphytes, Come out from the arial stems and remain hanging
in the air, and draw moisture from atmosphre through root hairs present on it. Moisture is
absorbed by these roots trough the outer layer of cell which have fibrous thickening that are
capable of absorbing moisture this layer is known as velamen eg. Orchids, Banda
B. Assimilatory roots : some of the arial root develop cholorophyll and take part in
manufacturing food. The aerial roots of Tinospora and submerged roots of Trapa (Water
chestnut) become green and synthesize food. Podostemon also has green assimilatory roots.
C. Sucking or haustorial roots or Parasitic roots : In parasitic plant (The palnts which obtain
shelter on the other plant know as host plant and also draw nutrition from them) roots enter in
the stem of host plant to absorbed nutrition from host. eg. Dendrophthoe, Cuscuta, Viscum,
Chandan
D. Reproductive roots : These are fleshy, adventitious roots which has bud and have capacity of
vegetative reproduction e.g., sweet potato (Ipomea batata), Dahlia, Bombax ceiba, Anogeissus
pendula
E. Leaf roots : In Salvinia, one leaf of each node modifies into root like structure for balancing
the plant in water

11. F. Respiratory roots : Halophyte or mangrove grow in oxygen deficient marshy area.
Some branches of tap root in these plant grow vertically & comes out from soil. These
roots are called pneumatophores through which air entered inside the plant. eg.
Rhizophora, Heritiera, Sonaratia and other mangrove plant.

12. FUNCTIONS OF ROOT
• Fixation (Primary function)
• Absorption of water and minerals
• Storage of food
• Conduction of water
• Photosynthesis and respiration
Importance of root study
• Roots hold soil and prevent soil erosion
• Knowledge is helpful in nursery practices and planting out seedlings in field
• Study of roots helps to selection of species for afforestation
• Principal of weed eradication also depends on nature of root system