My Dear viewers:
In this blog we will discuss about the Plant Morphology in brief
Plant morphology “represents a study of the development, form, and structure of plants.
So in this blog we will discuss the different forms of a plant parts and their functions like
Root: In vascular plants, the root is the organ of a plant that typically lies below the surface of the soil. Roots can also be aerial, that is growing up above the ground.
There are two types of roots Tap root and Fibrous root
The main root that grows almost vertically down into the soil. It is broad near the base of the stem and tapers towards the tip or apex. Branches and Sub-branches come out from this main root and get spreaded out in the soil. Eg. Sunflower and mustard
The depthless or adventitious roots. Eg. Rice
Regions of root:
1. Root cap region
- Growing region
- Root hair region
- Permanent region
Modification of root:
- Underground modified root: Radish (fusiform), Carrot (conical), Turnip (napiform) and Sweet Potato
Function: Storage of food
- Prop Root: Banyan tree
- Climbing root: Money plant
Function: Helps in climbing
Functions of root
1. Roots goes into the soil and fix the plant firmly to the ground
- Roots absorb water and minerals from the soil
- Roots hold on to soil particles and prevent the soil erosion
- Roots absorb the water and mineral and transport the same to the stem, which finally go to the leaf formanufacturing of food materials
- Some Roots provide additional support to the plant
- Roots also store food
- Roots also help to take oxygen directly from air in halophytes, which grow in the physiologically dry soil. They are called pneumatophores
In vascular plants, the stem is the organ of a plant that typically lies above the surface of the soil. Stems can also be seen below the surface of the soil, which are called underground modified stem
Different features of stem
- Some trees have very strong stems called trunk
- Trunk has protective covering called bark
- Shrubs have hard and bushy stem
- Herbs have soft stem
- Climbers and creepers have week stem
- Bamboo have hollow stem
- Stems do have joints called nodes
- The portion of the stem between two nodes is called internode
- At the tip there is a bud called apical bud
- Buds that grow at the junction of a leaf and stem are called axillary bud
Buds are of two types, which are in the following
- Vegetative bud: From which branches and leaves are grown
- Floral bud: From which flowers are grown
Cabbage is the largest bud
Modifications of Stem:
Sometime stems get modified and remains underneath the surface of the soil. These are called underground modified stem. Their function is to store foods
- Potato (tuber)
- Onion and Garlic (bulb)
- Ginger and turmeric (rhizome)
- Amorphophallus (Corm)
The Axillary bud of some plants like Gourd and Passion Flower gets developed into coiled structures called tendrils. These tendrils twine around some support like a post or a tree and help the plant to climb
Potato and Onion can produce new plant through underground modified stem.
Chrysanthemum and Rose can produce new plant through stem by cutting process
Sometimes the axillary buds transforms into thorns, it protects the plant from herbivorous
- Storage of water and manufacturing of food:
The green stem of cactus produces food as well as preserve water
Functions of Stem
- It bears leaves, buds, flowers and fruit
- It carries water and minerals from the root to the leaves (Ascent of Sap)
- It distributes food to all parts of the plant (Translocation of food)
- It stores reserve food matter for the future use
- It provides additional support to climb with the help of stem tendril
- It also produces new plant through vegetative mode of reproduction
- It also helps the plant to defend by the formation of thorns from axillary bud
The leaf is a flat green outgrowth of the stem, which grows from the node and bears a bud in its axil
Different features of leaf
- Stalk or petiole: The thin portion of the leaf by which it is joined to the stem is called the stalk or petiole
- The midrib: The extended portion of petiole into the leaf
- Leaf base: It is the region where petiole joins with the stem
- Veins: The thin lines arising from the petiole and midrib and spreading across the leaf
- Veinlets: The veins provide support to the leaf and carry water, minerals and food.
- Venation: The arrangement of veins on a leaf is called venation
- Reticulate venation: Veins get spreaded out in all directions. Eg. China rose, mango, guava
- Parallel venation: When the veins run parallel to each other. Eg. Rice, wheat, banana
Functions of the leaf
Types of leaves:
- Simple leaf: Undivided leaf blade. China rose, mango, guava
- Compound leaf: Divided leaf. Rice, wheat, banana
Arrangement of leaves (Phyllotaxy)
In different plants leaves are arranged differently to get as much sunlight as possible
- Alternate: Leaves are arranged in alternate fashion. China rose
- Opposite: When two leaves grow from same node. Guava, basil, and Calotropis
- Whorled: Leaves are in circular arrangement. Oleander and devil
Modification of leaf
- Support: To provide support to the weak stem some leaves get modified into tendrils. Pea
- Reproduction: Some plants do reproduce through their leaf buds. Bryophyllum
- Defense: Some plants like cactus the leaves are turned into spines to reduce transpiration and protect the plants from herbivores
The reproductive part of a plant
Four Whorls of a flower
- Calyx (sepal): Green Function- Protection
- Corolla (petal): Colourful Function- Attract insects for pollination
- Androecium (stamen): Stamens are male reproductive part contain filament and anther at the tip, which contains pollen
- Gynoecium (pistil): Contain one or more carpels or reproductive parts- Style, Stigma and Ovary
Types of Flowers
- a) Unisexual flower: Either Androecium or Gynoecium is present. Gourd and Papya
- b) Bisexual flower: When both Androecium and Gynoecium are present. China rose
- c) Regular flower: Symmetrical flower. Rose
- d) Irregular flower: Asymmetrical flower: Sesbania
It is the transfer of pollen grains from the anther to the stigma of they gynoecium
Pollination is of two types
- a) Self Pollination: When pollination takes place within the same flower. Pea
- b) Cross Pollination: When pollination takes place within the different flower. Eg Gourd, papaya
It is process by which male gamete unites with the female gamete to form a single cell called zygote.
Fertilization in plants
Male parts: (Stamen) pollen grains or microspores are formed within the anther through the meiotic divisions of diploid microspore mother cell. Each pollen grain is binucleated unicellular structure it remains covered by a thin elastic membrane called intine, which is again externally protected by a tough wrinkled coat called exine. At some places the exine is absent and the intine remains naked there such a pore is called germ pore. Out of the two haploid nuclei one is called tube nucleus and the other is generative nucleus.
Female part: There are ovules inside the ovary of a flower each ovule carries an elliptical sac called embryo sac. This sac remains covered by two integuments that leave a fine gap one end of the embryo sac. This opening is called micropyle. In a matured ovule out of the three haploid nuclei placed inside the embryo sac towards the micropyle the middle one is the ovum or the megaspore form through the mitotic division of diploid megaspore mother cell. Along the central part of the embryo sac there remains a diploid nucleus called definitive nucleus, which is formed through fusion of two haploid polar nuclei.
Process: The pollen grains are transfer and to the stigma by the process of pollination. A pollen grain absorbs the stigmatic fluid, it swells up and as a result the intine pushes out through the germ pore to form the pollen tube the tube nucleus migrates at the tip of the pollen tube with generative nucleus following it. The pollen tube moves chemotropically towards the micropyle of the ovule via the style. In the mean time the generative nucleus gets mitotically divided into two haploid nuclei called the sperm nuclei, the male gametes. As the tip of the pollen tube touches the embryo sac the point of contact dissolves, tube nucleus disorganized and through the path thus described two sperm nuclei enter the embryo sac one of them fertilizes the ovum to form the diploid oospore.
Sperm nuclei (n) + ovum (n) = oospore (2n)
In gymnosperm the remaining sperm nucleus perishes, in angiosperm the remaining sperm nucleus unite with the definitive nucleus to form a triploid endosperm nucleus.
Sperm nucleus (n) + definitive nucleus (2n) = Endosperm nucleus (3n)
This act is known as double fertilization.
Fertilization: The endosperm nucleus through repeated division forms the special nutritive tissue in the seeds called endosperm or albumen.
Changes after fertilization:
- Ovary – fruit
- Ovules – seed
- oospore – embryo
- endosperm nucleus – endosperm
- integument – seed coats
Fruit is the fertilized ovum
A Fruit is the seed-bearing structure in flowering plants (also known as angiosperms) formed from the ovary after flowering. fruits are the means by which angiosperms disseminate seeds.
A fruit has two parts in drupe type of fruit
Pericarp and the seed
Pericarp again subdivided into epicarp, mesocarp and endocarp
Seed is the fertilized ovule, consisting of an embryo enclosed by a seed coat
There are two types of seed Dicotyledonous seed consisting of two seed leaf and Monocotyledonous seed consisting of one seed leaf
Gram (Dicotyledonous seed)
Seed coat: The outer covering of the seed, which are of two types
Testa: It is tough and brown in color, which is present outer most region of the seed
Tegmen: It is white and paperish in nature, which is present inner layer of Testa
Hilum: This is the point where the seed is attached to the fruit. It is a scar mark of the seed.
Micropyle: It is the minute pore through which water enters into the seed
Kernel: The portion of seed, which remains after removing the seed coat, which is of two types
- Cotyledons: an embryonic leaf in seed-bearing plants
- Tigellum or Embryonal axis
- Epicotyl: It contains Plumule, which is the rudimentary shoot or stem of an embryo plant.
- Hypocotyl: It contains Radicle, which is rudimentary root that develops into the primary root
Paddy is the monocotyledonous, albuminous seed.
Glumes: The grain is covered by four glumes third one is the largest. These are all make husk. The husk is
neither the part of seed nor the fruit
Grain: The grain contains coat and kernel
Coat: It contains the fusion of pericarp and seed coat. It is reddish or whitish in color
Kernel: Kernel contains Endosperm and Embryo
Endosperm: During polishing of rice the outer coat and embryo are removed, leaving a small break at one end
of the grain, which is known as Endosperm
Embryo: It contains Cotyledon or Scutellum and Axis
Axis: It contain plumule and radicle with coleoptile and coleorhiza
It is the process by which the embryo wakes up from the state of dormancy and takes to active life.
It needs water and oxygen mainly
There are three types of germination Epigeal, Hypogeal and Viviparous
- a) Epigeal germination: The hypocotyl grows rapidly and forms a loop like structure.
Eg. Gourd seed, tamarind and castor
- b) Hypogeal germination: Here the cotyledons remain in the same and the radicle comes out first.
Eg. Mango, pea, wheat and maize
- c) Viviparous germination: Here germination takes place within the plant. Here the radicle comes out from the
fruit. As the fruit gets detached from the plant body it gets embedded in the soil.
Eg. In mangrove like Heritiera fomes or Sundri plant
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