The first structures to appear from a germinating seed in the form of a radicle are the tree roots. It is geotropic and goes deep down into the soil in the form of tap root. The tree roots are fixing the plant with the substratum and absorbing water and nutrients from the soil.
Definition of tree roots (plant roots): –
The tree roots are the descending axis of the plants that develops from the radical, reforming the function of absorption of water and nutrients and fixation of the plant to the substratum.
Characteristics of tree roots: –
i) The root is the descending axis of the plant developing from the radicle.
ii) The tree roots are positively geotropic and hydrotropic and negatively phototropic in nature.
iii) They are colourless or non-green, due to absence of chloroplast.
iv) They contain leucoplast which helps in storage of food.
v) The tree roots never contain leaves, buds and flowers.
vi) They are undifferentiated into nodes and Internodes.
vii) Two types of tree roots are there are, those are tap roots and adventitious roots.
viii) Tree roots are differentiated into root-cap, growing region, root hair zone and the permanent zone.
ix) The root caps of the tree root protect the root apices.
x) The meristematic cells contain by the zone of elongation and it helps in the growth of root.
xi) The unicellular, exogenous tubular projection of epiblema of the root hair zone called root hairs help in the absorption of water.
xii) The permanent tissue contains by the permanent region is not in the active state of division.
xiii) The normal function of the tree roots are attachment, absorption and storage.
xiv) The special function of the tree roots include assimilation, absorption of air, supporting mechanically, providing epiphytic or parasitic adjustment.
Types of tree roots: –
The tree roots may be classified into two major types on the basis of the origin of roots, those are (1) true roots and (2) adventitious roots.
What are the true roots?
Tree roots which develop directly from the radicle or its branches are known as true roots. Sometimes it may say as normal roots. From the primary root the radicle are going deep into the soil in dicot plants, the primary roots give rise to lateral branches known as secondary roots and they also give rise to the tertiary roots .
What are the adventitious roots?
Tree roots which do not develop from the radicle, but it developed from other parts of the tree are known as adventitious roots. In such case the radicle degenerates at an early age and is replaced by the tuft of adventitious roots. The adventitious roots are of three types. Those are the Couline roots, fibrous roots and foliar roots.
What is Cauline roots?
The Adventitious tree roots that develop solitarily or in groups either from the internodes of stems are called true adventitious roots or in the other name the cauline roots. Example : Banyan, Hydrocotyle , etc.
What are Fibrous roots?
A bunch of fibre-like tree roots, that develop from the base of the plumule after the death of primary roots are called fibrous roots. Example: Grasses. The primary tap roots developing from the radicle dies at early stage of development in the monocot plants. In this case, the primary roots developing from the base of the radicle and it is called seminal root.In case of wheat, paddy, etc., these seminal roots die off with the development of the plant and is replaced by the bunch of fibrous roots.
What are foliar roots?
The adventitious tree roots that develop from the various parts of leaves like leaf margin and petiole are called foliar roots. Example: Bignonia.