Concept of Plant Anatomy
- Plant Anatomy deals with the study of internal structure of various organs of Plants. It also includes the structure of cell, which is the Basic unit of all living organisms.
- N Grew and M Malpighi are considered as the Founder of Plant Anatomy.
- Tissue= A group of cells specialized for a Particular function or a set of similar function. The term Tissue is coined by N Grew.
- Plant Tissue can be categorized into Three groups for convenience of study-
- Meristematic Tissue
- Permanent Tissue
- Secretory Tissue
- Meristematic Tissue = A Meristematic Tissue is a group of immature cell that are preparing the divide or are in continuous state of Division. Meristem is coined by C Nageli in 1858.
- Permanent Tissue are formed as a result of division and differentiation in Meristematic tissue, while secretory tissue are large number of Plant that possess special cell or group of cell that secrete or excrete products.
Root Structure and Functions
- Root is the underground portion of plant that develops from the radicle of plant embryo.
- Root is generally, grow positively geotropic.
- Root does not bear leaves and therefore no nodes are Present into roots.
- There are two types of Root system that can be distinguished in Flowering Plants,
- Tap root system and
- Adventitious root system
- Di cotyledons possess tap root and mono cotyledons possess adventitious root system.
- Root apex is sub terminal in position because there is present root cap at apex.
Some Important Definition-
- Cortex = It composed of thin walled isodiametric perenchymatous cells with many intercellular space.
- Proto xylem = its element and usually a single vessels with annular thicking.
- Meta xylem = It has pitted, vessels, which are polygonal in cross section.
- Pith = It occupies a small area in the centre of Root.
- Phloem = It consists of sieve tube, companion cell and phloem parenchyma.
- Pericyclce = It’s formed the outer boundary of the Vascular bundle.
- Endodermis = It is composed of closely packed living cell. Some cell of epidermis usually the ones which lie opposite to protoxylem.
- Epiblem = Unicellular tabular prolongation (root hair absorption of water from the soil)
Theories of Root Apex
- There are three main theories of Root Apical Meristem (RAM) Theories-
- Korper kappe Theory = Given by Schuepp in 1917, According to this theory, the Root apices divide in two planes. First a cell divide transverslly then two daughter cells divide longitudinally. Thi sequence is termed as T-division.
- Apical cell Theory = This theory was given by Nageli in 1858. He observed a single tetrahedral apical cell in the root apices of a number of vascular cryptogams like algae, bryophytes, etc.
- Histogen theory = This theory was given by Hanstein in 1870, It is similar to histogen theory of SAM. Each of these three layer has a specific purpose (a) Dermatogen Epidermis, (b) Periblem cortex and (c) Plerome Vascular cylinder.
Stem structure and Functions
- The Stem develops from the plumule of the embryo, while lateral branches develop from auxiliary bud or from adventition buds.
- We are discussing the internal structures of di cotyledonous and mono cotyledonous stem.
Theories of Shoot Apex Organization
- There are two Shoot Apical Meristem (SAM) Theories-
- Tunica Corpus theory = This theory is given by Schmidt in 1924. It states that there are two distinct zones present in shoot apices tunica (outer) and corpus (inner).
- Apical cell theory = This theory was given by Hofmeister in 1857. It states that a single apical cell is the structural and functional unit of apical meristems and it regulates the whole process of Primary growth.
- It may be circular or angular.
- Epidermis = It is the outermost circular layer of the stem. It is the uniseriate and is made up of compactly arranged, tangentially elongated, Parenchymatous cell, Stomata are present.
- Cortex = It is divided into two zones-
- Hypodermis – Just below the epidermis are 3 to 5 layer collenchymatous tissue.
- General cortex – It consist of several layer of Parenchymatous cell.
- Endodermis = Its innermost layer of cortex which delimits if form the stele.
- Pericycle = It is made up of alternate bands of Parenchymatous cell.
- It is lacks secondary growth as it lacks cambium in vascular bundles.
- The various tissue are not arranged in concentric rings for example- Maize, grass and wheat, etc.
- Epidermis = It is outer most layer that is made up of Parenchyma cell. Epidermal hair are absent and stomata are present.
- Hypodermis = It is made up of Sclerenchyma that is below the Epidermis and Intercellular space are absent in this tissue.
It is Arpan Priy Das from west champaran, Bihar. Arpan started his blog about agricultural information named as “ECOHILLAGRI.COM ” He started his blog ecohillagri.com to help many agricultural or other students as well as farmers. so, it is necessary for them to learn about agriculture that is useful for students as well as farmers and that all concepts are present in this blog.