Plants : Structure and functions
Based on Maharashtra Board General Science Chapter 2
Theory
[responsivevoice voice="UK English Female" rate="0.8" pitch="0.8" buttontext="Listen to this"] Roots, Stem, leaves, flowers, seeds and fruits are the different parts of a plant. We can identify the plants with the help of this different characteristics.
Roots : The roots help provide support by anchoring the plant and absorbing water and nutrients needed for growth. They can also store sugars and carbohydrates that the plant uses to carry out other functions.
Plumule: The plumule is the rudimentary shoot of the seed embryo, which develops into the first true leaves. It is found above cotyledons during the germination of the seed. Plumule grows upwards out of the soil.
Radicle: The radicle is the first part of the embryo, which comes out from the seed during germination. Radicle grows downwards into the soil.
There are two main types of roots
1-Tap roots (In dicotyledonous plants)
2- Fibrous roots (In monocotyledonous plants)[/responsivevoice]
[responsivevoice voice="UK English Female" buttontext="Listen to this"] Tap root : Tap root is thicker at the base. It tapers towards the end. Tap root produced secondary roots. Secondary roots grow obliquely and spread far and wide in the soil. Tap roots support the plant.
Root hair : Hair-like processes near the root tips are called root hairs.
Root cap : In the region of the growth of the root, the tip is covered by a cap like structure. This is the root cap which protects the root-tip from injuries.
Fibrous Roots : Fibrous roots arise from the stem.
The roots of pea, mustard and coriander show growth of Tap root.
Sorghum and maize show fibrous roots.
Adventitious roots: Some roots grow from the stem just above the soil, these are called adventitious roots. Maize sugarcane and sorghum have two type of roots, adventitious roots above the soil and roots going under the soil.
Functions of the roots :
- Holding and anchoring the soil firmly
- Absorption of water and minerals
- Supporting the plant.
Modified roots & Its functions
(i) Aerial roots - Absorption of moisture from air
(ii) Stilt-roots - Supporting plant above the soil
(iii) Runners - Vegetative propagation i.e. reproduction
(iv) Breathing roots or Pneumatophores - Breathing
Prop roots : Prop roots are seen in banyan tree. These roots arise from branches and the grow towards the soil. Once reaching the soil they support the canopy of the huge tree.
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1- Stem Grows above the soil
2- The sprouting seed produces plumule. From the plumule the stem grows
3- Length of the stem gradually increases as the sprout grows.
4- Nodes on the stem are points from where the leaves come out.
5- Between two successive nodes is an internode.
6- The tip or the apical end of the stem is called a bud. [/responsivevoice]
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1- Leaves arise from the nodes on the stem.
2- Leaf-blade or lamina : The broad, spread out part of the leaf.
3- Leaf-margin : edge of the leaf
- Types of leaf margins : Entire, dentate and lobed
4- Leaf apex : tip of the leaf
- Types of the leaf apex : Tapering, pointed or rounded.
6- Petiole : The stalk of the leaf. Some leaves have petioles, some do not have petiole.
7- Leaf-base : The portion of the leaf attached to the stem.
8- Stipules : Small leaf like structure near the leaf base.
9- Types of leaves :
- Simple leaves : Single undivided leaf blade with single mid rib
- Compound leaves : Leaf-blades divided into many leaflets.
10- Arrangement of leaves ( Phyllotaxy ):
- The arrangement of the leaves on the stem is different in different plants
- Types of arrangement : Alternate, opposite, whorled, spiral etc.
11- Shape of the leaves : Rounded (obovate) palmate, lanceolate , linear etc.
| The venation pattern in maize leaf and peepul leaf are different |
Venation :
The pattern in arrangement of veins in the blade of a leaf is called as venation.
Two types of venation are reticulate venation and parallel venation.
Reticulate venation involves net-like pattern of arrangement of veins.
Most of the angiosperms with two cotyledons in the seed exhibit reticulate venation.
e.g. Rose, Maple, Tulsi, Hibiscus, Red gram etc.
Parallel venation involves smaller veins running parallel to each other.
Most of the monocot plants exhibit parallel venation in their leaves.
e.g. Grains, banana, palm, onions, and grass etc.
Leaves in monocots show parallel venation whereas leaves in dicots show reticulated venation. [/responsivevoice]
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1- Pedicel : The stalk of the flower is called pedicel. It may be long or short . One end is attached to stem.
2- Receptacle : End of the pedicel which is attached to the flower is enlarged and swollen. This is called recptacle
3- Calyx : Outermost whorl of the flower, green in color and protective in nature. The petals in bud condition are covered over by calyx.
4- Corolla : Petals make the corolla. Petals may be coloured or white.
5- Androecium : The male reproductive part of the flower which is made up of stamens. Each stamen has an anther and a filament.
6- Gynoecium : The female reproductive part of the flower which is made up of carpels. Each carpel consists of stigma. style and ovary.
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Pollination : is the act of transferring pollen grains from the male anther of a flower to the female stigma.
The goal of every living organism, including plants, is to create offspring for the next generation.
One of the ways that plants can produce offspring is by making seeds. Seeds contain the genetic information to produce a new plant.[/responsivevoice]
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Flowering plants generate pollen, ovules, seeds, and fruit.
Fertilization in flowering plants happens through a process called pollination.
Fertilization occurs when one of the sperm cells fuses with the egg inside of an ovule. After fertilization occurs, each ovule develops into a seed. [/responsivevoice]
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1- Each fruit has its own specific characteristics.
2- The variations in fruits are with respect to their shape, color, taste, skin or shell, flashy part and seed etc.
3- Fruits like cashew, has its seed, outside the fruit.
4- Dicotyledonous seeds can be divided into two equal parts. Monocotyledonous can not divided into two equal parts. [/responsivevoice]
Exercise Solutions
1- The part that grows from inside the seed towards the soil is called.........
Answer : radicle
2. ......... are the hair-like processes near the root tips
Answer : Root hairs
3. Monocotyledonous plants have ......... roots
Answer : fibrous
4. The part of the stem between two nodes is called an ............
Answer : internode
5. The broad spread-out part of the leaf is called.......while its tip is called the........
Answer : leaf blade, leaf apex
6. In the bud condition the petals are covered by leaf like whorl called......
Answer : calyx
Question 1:
Give examples of 3 plants that have :
(a) Spiny fruits
Spiny fruits- jackfruit, breadfruit, black mulberry
(b) Spiny stem
Spiny stem – sago palm, rose ,cactus
(c) Red flowers
Red flowers– rose, cardinal, anthurium, hibiscus
(d) Yellow flowers
Yellow flowers – sunflower, roses, tulips
(e) Leaves which close at night
Leaves which close at night– tulips, hibiscus, poppies
(f) Single-seeded fruits
Single seeded fruits – mango, cherry, peach
(g) Many-seeded fruits
Many seeded fruits– Watermelon, guava, apple.
Question 2:
Observe any one flower and its various parts and describe it in your own words.
They different parts of a flower are:
1. Androecium (male reproductive organ) – The androecium consists of whorls of stamen. The stamen consists of the filament (long and slender stalk) and anther (bilobed structure). A typical anther is bilobed, which contains the pollen grains.
2. Gynoecium (female reproductive organ) − Gynoecium represents the female reproductive part made up of carpels. Carpel is made up of:
- Style − It connects stigma to the ovary.
- Stigma − It acts as a receptacle for the pollen grains.
- Ovary − It is the enlarged basal part on which style lies. Each ovary bears one or more ovules attached to cushion-like placenta. After fertilisation, ovules develop into seeds and ovary into fruit.
3. Calyx (accessory organ bearing sepals) − Calyx refers to the sepals.They are green in colour. They protect the plant in bud stage and also attract the insects for pollination.
4.Corolla (accessory organ bearing petals) − Corolla refers to the brightly coloured whorl of a flower. Individual unit of corolla is petals.Petals protect the inner essential organs (i.e., stamens and carpels) and attract pollinators since they are brightly coloured.
Question 3:
What are the similarities and differences between ?
(a) Jowar and Moong
|
Jowar
|
Moong |
| 1. It is a type of monocot plant. | It is a type of dicot plant. |
| 2. It has fibrous root system. | It has tap root system. |
| 3. The leaves of jowar plant show parallel venation. | The leaves of moong plant show reticulate venation. |
Similarity: Both jowar and moong are annual plants.
(b) Onion and Coriander
| Onion | Coriander |
| 1. It is a type of monocot plant. | It is a type of dicot plant. |
| 2. It is a type of vegetable. | It is a type of herb. |
| 3. The edible part is a bulb. | The edible part is leaf and stems. |
Similarity: Both onion and coriander are annual plants.
(c) Leaves of banana and mango
| Leaves of Banana | Leaves of Mango |
| 1. The leaves of banana are very long and have bifurcations on their edges. | Leaves of mango are short in size. |
| 2. It has parallel venation. | It has reticulate venation. |
Similarity: Both banana and coconut are perrenial plants.
(d) Coconut tree and Jowar stalk plant
| Coconut tree | Jowar stalk plant |
| 1. It can grow upto 15 – 23 metres. | It can grow upto 2 – 3 metres. |
| 2. Leaves of coconut trees are arranged spirally. | Leaves of jowar stalk plants are arranged in opposite manner. |
Similarity: Both have fibrous roots.
Question 4:
Explain the following images in your own words.
Image A represents a seed and its cross section. The seed consists of seed coat, cotyledon and an embryo. A seed coat is the outer covering of a seed. It is hard in nature and thus provide protection to the inner delicate parts of a seed. This embryo is thick and swollen due to the presence of food reserves.
Image B represents a monocot and a dicot seed. A monocot seed is made up of a single cotyledon called scutellum. It has a relatively small embryo which contains endosperm.
Question 5:
Describe the functions of various parts of a plant.
They different parts of a flower are:
-
Androecium
-
Gynoecium
-
Calyx (accessory organ bearing sepals)
-
Corolla (accessory organ bearing petals)
Androecium (male reproductive organ) − The androecium consists of whorls of stamen. The stamen consists of the filament (long and slender stalk) and anther (bilobed structure). A typical anther is bilobed, which contains the pollen grains.
Gynoecium (female reproductive organ) − Gynoecium represents the female reproductive part made up of carpels. Carpel is made up of:
-
Style − It connects stigma to the ovary.
-
Stigma − It acts as a receptacle for the pollen grains.
-
Ovary − It is the enlarged basal part on which style lies. Each ovary bears one or more ovules attached to cushion-like placenta. After fertilisation, ovules develop into seeds and ovary into fruit.
Calyx − Calyx refers to the sepals.They are green in colour. They protect the plant in bud stage and also attract the insects for pollination.
Corolla − Corolla refers to the brightly coloured whorl of a flower. Individual unit of corolla is petals.Petals protect the inner essential organs (i.e., stamens and carpels)andattract pollinators since they are brightly coloured.
Question 6:
Certain properties are mentioned below. Find a leaf corresponding to each property and describe those plants.
leaves with smooth surface, leaves with rough surface, fleshy leaf, spines on leaf.
Leaf with rough surface: Asperifolia is a type of plant which has rough leaves. It belongs to the category of shrubs.
Fleshy leaves: Plants with fleshy leaves are called succulents and are usually found in areas like deserts. Their leaves are green and fleshy because they store water in them which can be used under adverse conditions. For example, opuntia.
Spines on leaf: Many plants have spines on their leaves. It is a way of protecting themselves from being eaten and destroyed by animals. For example, Acacia and aloe vera.
Question 7:
Find the plant parts.
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| c | n | e | t | a | 1 | c | e |
| a | v | o | v | u | m | l | r |
| p | e | t | a | 1 | s | e | o |
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What is a root ?
The roots help provide support by anchoring the plant and absorbing water and nutrients needed for growth. They can also store sugars and carbohydrates that the plant uses to carry out other functions
Root is the part of plant that grows into the ground from the radicle of the sprouting send.
The root cap is at the end root.
A root grow is secreted
What is a stem?
Stem is the part of the plant which grows above the soil from the plumule of the sprouting seed.
Textbook pdf
chapterwise available on Class 7th MSBSHSE – General Science page