INTRODUCTION
ANATOMY OF FLOWERING PLANTS:-
- Anatomy of flowering plants, study of internal structure of plants.
- Internal structures also show adaptation to diverse environments.
ANATOMY OF FLOWERING PLANTS-THE TISSUES
- Group of cells having a common origin and usually performing a common function is called tissue.
TYPES
Meristematic tissues and Permanent tissues
Meristematic tissues
- Actively dividing cell
- Two types according to appearance in life
- Primary meristem (appear early in life)
(i) Apical meristem:-
- Found at tips roots and shoots
- Some shoot apical meristem cells that are left behind during stem elongation and leaf formation constitute axillary buds.
- Axillary buds are capable of forming a branch or a flower
(ii) Intercalary meristem
- Occurs between mature tissues
- Occurs in grasses, regenerate parts removed by grazing herbivores.
2. Secondary meristem (appear later than primary meristem)
- Also called Lateral meristem
- Cylindrical meristem found in mature regions of roots and shoots.
TYPES
⇓
(a) Intrafascicular Meristem:- Found betweenxylem and phloem in a conjoint vascular bundle.
(b) Interfascicular Meristem:- Found between two vascular bundles
(c) Cork Cambium:- Extrastelar cambium formed in cortical region.
Permanent tissues
- Newely formed structurally and functionally specialized cells
- Do not divide further
- Two types:- Simple and Complex
COMPLEX PERMANENT TISSUES (MADE OF MORE THAN ONE TYPE OF CELLS)
TYPES
- Xylem ( Four components):-
(i) Tracheld
- Elongated, tube like with tapering ends,lignified,dead and without protoplasm
- Water transporting element
(ii) Vessel
- Long cylindrical tube, absent in gymnosperm
- Multicelled, dead, devoid of protoplasm, lignified with large central cavity
- Main water conducting element in angiosperms
(iii) Xylem Parenchyma
- Living, thin walled
- Involved in radial conduction of water, may store food
(iv) Scierenchyma Fibres
- Dead, lignified wall with obliterated lumen
2. Phloem (Four components):-
(i) Sieve tube elements (Gymnosperms have sieve cells)
- Long, tube like, perforated end walls, lack nucles at maturity
- Peripheral cytoplasm with large central vacuole
- Transport of food material
(ii) Companion cell (Gymnosperms have albuminous cells)
- Specialised parenchyma cell, connected to sieve tubes by pit fields
- Helps to maintain pressure gradient in sieve tubes.
- The functions of sieve tubes are controlled by the nucleus of companion cells.
(iii) Phloem parenchyma:-
- Elongated, tapering cylindrical cells.
- Stores food material, resin, mucilage, latex etc.
- Absent in most of the monocots
(iv) Bast fibres (Phloem fibres):-
- Elongated, scierenchymatous, unbranched, poited needle like apices
- Jute,flax and hemp produce commercial bast fibres.
- Generally absent in primary phloem but found in secondary phloem.
SIMPLE PERMANENT TISSUES (MADE OF ONLY ONE TYPE OF CELLS)
Parenchyma:-
- Forms major component within organs
- Spherical, oval, round,polygonal or elongated in shape
- Thin walled, living
- Cellulosic cell wall
- May have small intercellular spaces
Functions:-
- Storage
- Secretion
- Photosynthesis (if have chlorophyll)
Collenchyma
- Occurs in layers below epidermis
- Cells may be oval, spherical or polygonal in shape
- Thick walled, living
- Corners of cell deposited with cellulose hemicellulose and pectin.
- Intercellular space absent
Functions:-
- Provide mechanical support to growing parts of pants.
- May perform photosynthesis (if cells contain chloroplast)
Sclerenchyma:-
- Long,narrow cells with thick linified wall
- Dead
- May be elongated and pointed- sclerenchyma fibre
- May be spherical, oval or cylindrical-sclereids (Common in fruit, nuts, pulp of guava, pear,etc.)
Function:-
- Mechanical support
Xylem types:-
- Primary xylem
- Secondary xylem:- Formed during secondary growth.
1. Primary xylem types:-
(i) Protoxylem (First formed with narrow vessel)
(ii) Metaxylem (Later formed with broader vessel).
Phloem types:-
- Primary phloem
- Secondary phloem (Formed during secondary growth
1.Primary phloem types:-
(i) protophloem (first formed and have narrow sieve tubes)
(ii) Metaphloem (Later formed and have broad sieve tubes).
- Endarch:- Protoxylem lies towards pith/centre and metaxylem towards periphery e.g. stems.
- Exarch:- Protoxylem lies towards periphery and metaxylem towards pith e.g. roots
COMPARISON BETWEEN DICOT AND MONOCOT ROOT
COMPARISON BETWEEN DICOT AND MONOCOT STEM
THE TISSUE SYSTEM
Epidermal tissue system
- Forms outermost covering of plant body
Epidermis→ Parenchymatous, usually single layered, outermost covering
- often covered by waxy cuticle (absent in roots)
Stomata→ Consist of guard cells and subsidiary cells
- Bean/kidney shaped guard cells- Dicot and dumbell shaped- monocot
Stomatal aperture+guard cells+subsidiary cells=stomatal apperatus
Root hairs→ unicellular elongation of epidermal cells
- Absorb water and mineral from soil
Trichomes→ In shoot system usually multicellular
- Branched/unbranched, soft or stiff
- Can be secretory, prevent water loss
GROUND TISSUE SYSTEM
In leaves
- Ground tissue consists of thin walled chloroplast containg cells called mesophyll
In stem and root
- Made up of all the tissue except epidermis and vascular bundles
- Consist of parenchymatous cortex, pericycle, pith,medullary rays and conjuctive tissue (between xylem and phloem in roots)
- Hypodermis- found in stem absent in roots
VASULAR TISSUE SYSTEM TYPES
presence/ absence of cambium
- open-cambium present e.g., dicot stem
- closed-cambium absent e.g., monocot stem
consists of xylem and phloem
according to arrangment of xylem and phloem
conjoint- Xylem and phloem on same radius e.g., stem, leaves
radial- Xylem and phloem are on different radii in alternate manner e.g., root
COMPARISON BETWEEN DICOT AND MONOCOT LEAF
SECONDARY GROWTH
- Occur in most dicots to increase girth
- Tissue involved are lateral meristem- vascular cambium and cork cambium
Vascular Cambium
- Form secondary vascular tissues
- Formation-:In dicot stem formed by interafascicular cambium and intrafascicular cambium (formed by dediffrentiation of cells of medullary rays)
- Activity: vascular cambium cuts off cells
Vascular pith
form secondary xylem
- Since cambium is more active towared innerside, thus amount of secondary xylem produced will be more than secondary phloem
- Primary and secondary phloem gradually get crusged while primary primary xylem remains more or less intact
- Vascular cambium also produces secondary medullary rays in radial direction
Cork cambium
- Replaces outer broken cortex and epidermis
- Formation: in dicot stem formed by differentiated of cortex cells
- Couple of layer thick and composed of narrow thin walled nearly rectangular cells
- Activity: phellogen or cork cambium cuts off cells
- Towards outer side form suberin deposited impervious cells, cork/ phellem
Towards inner side
Form parenchymatous secondary cortex, phelloderm
- Phellem+ phellogen+ phelloderm→ periderm
- Bark: NON- technical term reffering all tissues exterior to vascular cambium, it can be early bark (produced early in the season ) or late bark (produced in the end of season)
Lenticels:
- Lense shaped opening formed by reputing of epidermis
- At certain region phellogen produces closely arranged parenchymatous cells.
- Permit gaseous exchange in woody parts.
DIFFERENT TYPES OF WOODS
Spring wood Autume woods
1. Form in spring season. 1. Form in autumn season.
2. Also called early wood. 2. Also called late wood.
3.Cambium usually more active in spring. 3.Cambium is less active in autumn.
4. Contains more xylary elements. 4. Cambium fewer xylary elements.
5. Vessels have wider cavities. 5. Vessels have narrow cavities.
6. Lighter in color, lower density. 6. Darker in color, higher density.
SPRING WOOD+AUTUMN WOOD⇒ ONE ANNUAL
Heart wood Sapwood
1.Secondary xylem of centre most region 1. Formed by secondary xylem of peripheral region
2. Dead with lignified wall, 2. Living
3. Dark in color, hard, durable
4. Deposited with tanin, resin etc. 4. Lighter in color
5. Do not conduct water but 5. Involved in conduction provide mechinical support of water and minerals
SECONDARY GROWTH IN ROOTS
Occurs through
↓
Vascular cambium Cork cambium
1, Completely secondary in origin 1. Formed by cells of pericycle, rest activity is similar to dicot stem
2. formation: by
- A portion of pericycle
- tissues just below pheloem
3. Activity: similar to dicot stem
In roots, cambium do not show seasonal activity
- Endomermis is innermost layer of cortex in roots and dicot stem
- primary meristem contribute to the formation of primary plant body
- Secondary meristem are responsible for producing secondary tissue
- stele: All tissues on the innerside of endodermis such as pericycle, vascular bundles and pith.
FUNFACT-
Did you know that the intricate network of veins in a leaf is similar to our own circulatory system, transporting nutrients and water throughout the plant?
In some plants, like the water lily, leaves are specially adapted to repel water, keeping them dry and buoyant even when submerged.
Flowers often have unique shapes and colors to attract specific pollinators, such as bees, butterflies, or birds, making them nature’s colorful advertisements.
The seeds of some plants, like the maple tree, have “helicopter” wings that help them spin and glide through the air, aiding in dispersal.
The bark of trees not only protects them from external threats but also serves as a record of their growth, with each ring representing a year of growth.
Some plants, such as the Venus flytrap, have specialized structures like traps or sticky surfaces to catch and digest insects for additional nutrients.
The roots of many plants, like carrots and beets, store reserve food in the form of starch, providing energy during periods of dormancy or growth.8.
The pineapple is a unique fruit formed by the fusion of individual berries into a single mass, with each “eye” representing a separate flower.
The bracts of plants, such as poinsettias, are often mistaken for flowers but are actually modified leaves that serve to attract pollinators or protect developing flowers.
- The stamen, or male reproductive organ of a flower, often resembles a miniature sword, lance, or spear, showcasing nature’s creative designs in the plant kingdom.
FAQ’s
Plant anatomy is the study of the internal structure and organization of flowering plants, including their roots, stems, leaves, flowers, and reproductive organs.
Flowering plants have several main parts, each with specific functions. Roots anchor the plant, absorb water and nutrients, and store reserves. Stems provide support, transport water, nutrients, and photosynthetic products, and serve as the site of growth. Leaves perform photosynthesis, regulate gas exchange, and transpire water. Flowers are reproductive structures involved in pollination and seed production.
Plant cells are organized into tissues, which are grouped into organs such as roots, stems, and leaves. Tissues include dermal, vascular, and ground tissues, each with specialized functions in protection, transport, and storage.
Vascular tissue, composed of xylem and phloem, transports water, nutrients, and sugars throughout the plant. Xylem conducts water and minerals from roots to shoots, while phloem transports sugars and other organic compounds from sources (such as leaves) to sinks (such as roots or developing fruits)
Plants exhibit various anatomical adaptations to cope with environmental conditions. For example, desert plants may have thick cuticles and sunken stomata to reduce water loss, while aquatic plants may have air-filled tissues for buoyancy and efficient gas exchange.
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