Ability to understand the functions of different parts of the Plants . / 2019

           We have great pleasure in offering to you this General Science Post / Article , You have acquired some knowledge of Science from your Environment Science  Post. Last post , however you began to study The Care of Plants From a separate General Science Article. The basic purpose of this post can be said to be 'Understand and explain to others'. You will learn Science through many activities such as Observe and Discuss, Use your brain power ! Find Out, Think about it, etc. Do take part in all these activities. to revise the science you have already learnt. Do tell us about the parts that you like as well as about the difficulties you face as you read and understand and study this Article. we are especially eager to know about the questions that come to your mind as you study science. Do write to us about them. 

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Learning Outcome : Ability to understand the functions of different parts of the Plants .

         A great variety of plants is found on the earth. Some plants have colouful flowers. Some plants grow in water whereas some are to be found in deserts which have a scarcity of water. Some plants are found only in snowy regions. Some plants cannot be seen without a microscope whereas some are huge in size. Like plants, animals too show diversity. Some are unicellular, others, multicellular. Some are vertebrates whereas others are invertebrates. This world is full of a variety of animals - aquatics, terrestrial, amphibian, reptilian, aerial, etc. 

         Are the plants and animals from Kashmir and Rajasthan of the same type ? Can you elaborate on any differences between the two ?

      Coniferous trees like pine and deodar flourish in snowy regions like Kashmir. However, in the desert of Rajasthan, plants like cactus and acacia [babhul] are to be found. The camel, a desert animals, is not found in Kashmir. What is the reason for these differences ?

Adaptation : Gradual changes occur in the body parts and also in the behavior of organisms which help them to adjust to their surroundings. Such changes are called adaptations. They take place over a long period of time.

         Visit various water bodies such as a river, brook, pond, lake, in your surroundings. What different do you observe between terrestrial and aquatic plants ?

         Some of the aquatic plants are firmly rooted in the soil at the bottom of the water bodies. Their stems are submerged, while leaves and flowers float on the surface. However, some plants are entirely afloat. Their roots are not anchored in the soil. The surfaces of leaves and stems of many aquatic plants are covered with a waxy layer. Leaves of some aquatic plants are thin and slender like a ribbon . This shape helps them to withstand fast currents of water. Air spaces in stems and petioles of aquatic plants are useful for floating in water.

Q. Why does water trickle off lotus leaves ?

A. The water trucks off of the leaves of lotus because their leaves have a waxy coating. The waxy surface of the lotus leaf is quite rough. When water drops fall on this surface, they roll down, carrying dirt particles with them. The wax is also capable of self - regeneration.

Q. Why don't the leaves of these plants rot in water ?

A. The leaves of aquatic plants are well adapted to withstand the wet conditions of the water. Most of their leaves have waxy coatings on them so that water is not absorbed by them. Some of them like Lotus, also contains thick layer of cuticle which helps them to withstand the moist condition. For these reasons the leaves of the aquatic plants do not rot in water.

Q. Why are their roots short and fibrous ?

A. The Lotus plant is an amphibian plant. This is the reason it has fibrous and short roots. It has short roots on the ground that there is sufficient water in its surrounding while the fibrous roots enable it to float and pick up lightness. Louts requires less support from the root so, they are short and fibrous.

Adaptation in desert plants :

Try : Take two potted plants - one, a cactus and the other, a leafy plant. Tie plastic bags loosely around the leaves of these plants and keep them in sunlight from early in the morning. In the afternoon, bring those pots into the classroom and observe them.

       Has the same quantity of water collected in both bags ?

       Desert plants are either leafless or their leaves are like small needles or have been modified into thorns. As a result, they lose very little water by evaporation. The stem stores water and food and is therefore fleshy. The stems are green as they perform. Photosynthesis in the absence of leaves. Their roots penetrate deep into the soil and some roots spread away into the soil in search of water. There is a thick layer of a waxy substance on the stems of these plants, too.

Adaptation in plants of snowy regions : 

       In what way are sloping branches useful to plants in a snowy region ?

      Plants of snowy regions mainly include conifers like deodar and pine. These trees are conical in shape due to their sloping branches. In the heavy snowfall and extreme cold in these regions, their conical shape prevents the snow from accumulation on the tree and the thick bark helps the tree to withstand the cold.

Adaptation in plants of forest regions : A variety of plants - trees, shrubs and herbs - are found in forests. These plants compete amongst themselves for sunlight. Hence, trees grow tall to get sunlight and climbers and vines grow to a great height with the support of trees. Spring - like tendrils on the stems of some climbers is an example of adaptation.

Adaptation in grassland plants : Diverse types of bushes and grasses are found in the grasslands. Fibrous roots of grasses prevent soil erosion. Forests in the equatorial region are dense. Animals like tiger, elephants and deer can remain hidden in these grasses. However, grasses in cold regions are very short. Animals like the rabbit are found in such grasses. vast meadows are found in hilly areas as well as plains.

Observe and note down the adaptations in the parts of plants like potato, groundnut, yam water hyacinth, aloe, acacia, carrot, onion, beet, bitter - gourd, grape vine etc. and other plants in your surroundings.

Adaptation for ingestions of food in plants : Most of the plants are anchored in the ground and are autotrophic. However, plants like dodder (cuscuta) are parasitic. The plant body of dodder consists of yellow wire - like stems. It is leafless and cannot perform photosynthesis. However, it has haustoria (sucking) roots for absorbing nutrients from the host plant. These roots penetrate up to the conducting vessels of the host plant to absorb water and food. Fungi  do not have chlorophyll and cannot perform photosynthesis. They obtain food from starchy foodstuffs like bhakri and bread. 

    

    They have root - like fibers for absorption of food. Plants need nitrogen, phosphorus and potassium for growth. Plants that grow in soil which is deficient in nitrogen, like drovers (sundew) , Venus flytrap, pitcher plant etc. Fulfill their need for nitrogen by consuming insects. Adaptations are seen in these plants which  serve to attract insects and hold them captive.

Plants : Structure and Function 

Q. What helps us to easily identify the plants around us ?

A. The most important thing that identifies plant around us is obtaining oxygen. Oxygen is obtained by the plants as a by product by the plants. We get fresh air from the trees, it helps to reduce soil erosion. if the plants were not there the there will be opposite happening here. So these prove that there are plants around us. 

Q. Which are the various parts of plants ?

A.  Parts of plants are Roots, branch, stems, leaves, flowers and Fruits etc.

           The root,  stem,  leaves,  flowers,  fruits, etc. of different plants are different. We can identify plants with the help of these different characteristics. Let us mow acquaint ourselves with these plant organs in greater detail.

Try : 1) Keep a moistened ball of crumpled paper in a conical flask. Place some soaked moth beans / gram seeds in the flask between the paper and the glass wall. Observe and note the changes in the seeds in two or three days.

Root : The part that grown from inside the seed towards the soil is called the radicle and the part that grows above the soil is called the plumule. The root that forms from the radicle, grows into the ground. The root is thick near the ground and gradually tapers to a pointed end. This part of the plants growing below the soil for support is called 'root'. Roots of some plants produce secondary roots, that grow obliquely and spread far and wide in the soil. Roots support the plants. This type of root is called a tap root. Roots bear hair-like processes near the root tips. These are root hairs. The root tip is delicate. This is the region of the growth of the root. The tip is covered by cap-like structure called the root cap. The root -cap protects the root-tip from injuries. 

        (2) Take a glass jar and fill three-quarters of it with water. Place an onion on the mouth of the jar in such a way that its roots are towards the water. Observe the growth of the roots for eight days. Thread-like or fibber-like roots arising from the stem are called fibrous roots. Thus, there are two main types of roots : tap roots and fibrous roots. Dicotyledonous plants have tap roots while monocotyledonous plants have fibrous root. Thus, there are two main types of roots : tap roots and fibrous roots. Dicotyledonous plants have tap roots. while monocotyledonous plants have fibrous roots. 

      (3) Sow the seeds of plants lie mustard, sorghum (jowar), maize (corn), pea, coriander, etc. in an earther pot. Cultivate the plant for eight days. Once the plants grow 15 to 20 cm high uproot them carefully while the soil is moist and put them gently in a large conical flack containing water. The soil will get washed off without any harm to the roots. Observe the roots carefully to see which plants have tap roots and which ones have fibrous roots. 

       Plants like maize, sugarcane, sorghum have two types of root. Some roots are underground whereas some grow from the stem just above the soil. The latter are called adventitious

 roots. Besides the normal functions like absorption of water and minerals, anchoring and supporting the plants, roots perform some other function too. Roots show some modifications to perform these additional functions. Some examples of such modified roots are aerial roots, stilt- roots, runners, breathing roots (pneumatophores), etc.

        (4) Take some water in a small glass jar. Put a plantlet in it in such a way that its roots are dipped in the water. Mark the water-level on the jar and add 5ml of oil to the water. 

Q. What would have happened if plants like tamarind, banyan and mango had fibrous roots?

A. If plants like tamarind, banyan and mango had fibrous roots, these trees would not survive or grow. Fibrous roots consist of many thin fibers arising in clusters. They are shallow and cannot go deep into the soil. The plants with these roots cannot withstand drought and can dry out quickly.

Q. What will happen if the root-tip is injured ?

A. If the root tip gets injured, the plant will not able to grow at the required rare.

Explanation : When the root tip gets injured, the root fails to penetrate the soil much. This means that the plants will get lesser nutrition from the soil. 

          Root supply the plants with the required water and nutrition that plants need to grow and develop. If the root fails to penetrate the soil, the plants do not get the required nutrition and thus the plant will not grow and may soon die.

Q. Which types of roots do the fenugreek, spinach and onion plants have?

A. Tap roots are present in fenugreek, spinach and onion plants. Tap roots are the roots, that grow vertically downward. They are thick and long in nature. Lateral roots originate from the central long root. They are usually seen in dicots. Other example of plants having tap roots are - parsley, carrots. Roots other than tap roots are - fibrous roots, prop roots and adventitious roots.

Roots emerging from the trunk and branches of a banyan tree grow towards the soil. These roots are called prop roots. What could be the use of these prop roots ? In the beginning, the banyan tree has very few prop roots. But later on, their number increases so much that it appears like a small forest. In Kolkata, a 250 years old banyan tree in the Indian Botanical Garden covers a very large area. It is supported by thousands of prop -roots. Is there any such tree in your neighborhood?

Q. Why are the underground parts of plants like radish, carrot, beet and sweet potato thick, fleshy and swollen ? Which part of the plants are they ?

A. The Underground of any plant are called as Roots. Roots of radish, carrot, beet and sweet potato are called tuberous roots because they are thick fleshy and swollen. These special roots store the nutrient's and hence appear thick, fleshy and swollen. Tuberous roots can be further classified into simple tuberous roots and fasciculate tuberous roots. 

Stem : The stem grows above the soil from the plumule of the sprouting seed. As the sprout grows the length of stem gradually increases, too. There are nodes on the stem. Leaves come out at the nodes. The part of the stem between two nodes is called an internode. The tip or the apical end of the stem is called a bud. Observe a branch of any plant and identify its different parts as per the diagram.

Leaf : Leaves grow from the nodes on a stem. Leaves are generally thin, flat and green in colour. The broad, spread -out part of the leaf is called the leaf-blade or lamina and its edge is called the leaf-margin. Leaf margins may be entire, dentate or lobed. The tip of the leaf is called the leaf apex. It may be tapering, pointed or rounded. Leaves of some plants have a stalk called a petiole. Leaves of some plants do not have a petiole. The portion of the leaf attached to the stem is called the leaf-base. Small leaf-like structures may be present near the leaf-base. These are called stipules. Do You see stipules in all plants ?

          Leaves of some plants have a single undivided leaf blade and a single mid-rib. Such leaves are called simple leaves. However, the leaf-blade of leaves in some plants is divided into many small parts called leaflets. Such leaves are called compound leaves. Simple leaf and compound leaf are the two main types of leaves.

      Observe a branch of plants like rose, neem, coriander, hibiscus, etc. In different plants the arrangement of leaves on the stem is different. It may be alternate, opposite, whorled, spiral, etc. According to shape, leaves are rounded (obovate), palmate, lanceolate, linear, etc.

Try : Take a peepal leaf and a maize leaf and observe them carefully. The peepal leaf is divided into two equal parts by a single mid - vein which lies along the mid -line of the leaf blade. Secondary veins arise from the mid-vein. They are branched and form a network or reticulum. On the other hand, in leaves of maize, all the veins are parallel, running from the leaf-base to the leaf apex. Thus, the peepal leaf-blade has reticulate venation and the maize leaf-blade has parallel venation.

        Observe the leaves of some other plants in your surroundings and identify the type of venation.

Try : 1. Carefully observe a fully opened hibiscus flower. Flowers may have a long or a short stalk called pedicel. One end of the pedicel is attached to the stem. The other end of the pedicel is expanded and swollen. It is called the receptacle. Petals and other parts of the flower are supported on the receptacle. Calyx, corolla, androecium, gynoecium are different parts of a flower. 

Calyx : In the bud condition the petals are covered by leaf-like parts called sepals which are green in colour. They form the calyx. 

Corolla : This is made up of colorful parts called petals. Observe the shape, colour and smell of the corolla of various flowers like the rose, chrysanthemum, hibiscus, mogara, kanher, tagar, etc.

Androecium : This is the male reproductive part of the flower. It consists of stamens. Each stamen is made up of anther and filament. 

Gynoecium : This is the female reproductive part of the flower. This is made up of carpels. A carpel consists of stigma, style and ovary. 

2. Take a vertical section of a hibiscus flower with the help of a sharp blade, by cutting the flower vertically from stigma to pedicel. Both sections of the flowers will be seen to have the same structure.

         After maturity, anthers burst and the pollen grains which are released fall on the stigma. This process is called pollination. Due to pollination, ovules (egg cells ) in the ovary get fertilized. Fertilized ovules form the seeds and the ovary develops into a fruit.

Q. Of what use to a plant are the insects flitting about around its flowers ?

A. The insects try to suck the nectar from the flowers and in that process the pollen grains stick to their legs. When they sit on another flower the pollen grain to the stigma and the pollination takes place. Thus, these insects help in the pollination .

Fruit : We eat many different types of fruits. Each type of fruit has its own characteristics. There are variations in their shape, colour, taste, etc. Mango contains only one seed where as jackfruit consists of many small fruitlets, each with its own seed.

       Observe the fruits of ber (ziziphus), mango, chikoo, apple etc. What do you observe? Each fruit has a different skin or shell, fleshy part and seed. In case of fruits like cashew, its seed is outside the fruit. 

      Soak the seeds of, pea, wheat, rice, jowar, groundnut in water for 3-4 hrs. Press the seeds with your fingers and observe them. Which seeds get divided into two equal parts ? Seeds which get divided into two equal parts are called dicotyledonous seeds. Seeds which do not divide into two equal parts are called monocotyledonous seeds.

 How do plants produce their own food ?

      plants are not parasitic in nature. They produce their own food with the help of their growth and nutrition. Plants make their own food by a process called Photosynthesis. Photosynthesis is a process used by plants and other organisms to convert light energy into chemical energy and stored in the form of starch which can be used later.  

      Plants also need food for their growth. They can produce their own food. With the help of sunlight and chlorophyll, plants make their food in their leaves, using water and nutrients from the soil and carbon dioxide from the air. This process is called as photosynthesis. Plants convert light energy into chemical energy and store it in the form of food. Water, minerals and salts are absorbed by roots from the soil. The stem transport them up to the leaves. The leaves have microscopic openings called stomata through which they take in the CO2  From the air. The chloroplasts present in the leaves contain chlorophyll, which absorbs sunlight, helping to convert carbon dioxide and water into food. Oxygen is given out in this process.

       Besides leaves, photosynthesis takes place in some other parts like green stems, too, as they contain chlorophylls.

Q. How does photosynthesis occur in dark red or purple coloured leaves ?

A. In photosynthesis, plants convert light energy to chemical energy. Typically, chlorophyll absorbs mostly red and blue light to excite the electrons in the photosystems for photosynthesis. Their color is the complementary color of the light they absorb. Hence, plants with more chlorophyll will appear green as they absorb little green light. Chlorophyll will appear green as they absorb little green light. Chlorophyll is known as the primary pigment.

Transport system in plants : Take a pumpkin stem having 2-3 leaves. Cut it under water with a sharp blade. Take some water in a conical flask and add 7-8 drops of ink to it. Put the pumpkin stem vertically in that flask. Observe the changes that  take place in it and discuss them in the classroom. The transport system of plants consists of the xylem and the phloem. The xylem transports minerals and water from the root to all aerial parts of the plants. The phloem transports the food (glucose, etc.) from the leaves to other parts of the plants where it is either consumed or stored. Though the plants have a transport system they do not have a separate digestive or execratory system.

Q. What is chemosynthesis ? Which plants produce their food by chemosynthesis ?

A.  Chemosynthesis is the biological conversion of one or more carbon - containing molecules and nutrients into organic matter. It uses the oxidation of inorganic compounds or methane as a source of energy rather sunlight. Sulphur bacteria and nitrosamines produce their food by chemosynthesis. 

Q. Which are the different substances excreted by plants ? why ?

        Plants produce carbohydrates by the process of photosynthesis. Carbohydrates are made from carbon, hydrogen and oxygen. Proteins are made from carbon, hydrogen, oxygen and nitrogen. How do plants obtain the nitrogen necessary for the synthesis of proteins ?

       Air contains gaseous nitrogen. However. plants cannot utilize gaseous nitrogen. It needs to be fixed i.e. converted into compounds. Fixation of nitrogen occurs by biological and atmospheric methods.

Biological fixation of nitrogen : Two different types of micro - organisms can bring about biological nitrogen fixation. Root-nodules of leguminous plants contain the rhizobium micro-organisms. These micro-organisms absorb atmospheric nitrogen and converts it into its nitrate, a compound. Micro-organisms like azotobacterial are present in soil. They also convert atmospheric nitrogen into nitrates.

Atmospheric Fixation Of Nitrogen : Lightning (thunderbolts) occur in the rainy season. This causes atmospheric nitrogen and oxygen to react with each other to form nitric oxide (NO) which is again oxidized to form nitrogen dioxide (NO). The nitrogen dioxide dissolves in rainwater and is converted into nitric acid (HNO3) which gets added to the soil along with the rain-water. This acid reacts with different minerals in the soil and convert into salts. Plants use this nitrogen salts for their growth.

Symbiotic nutrition : In some cases, two or more than two different types of plants live together to fulfill their needs of nutrition, protection, support, etc. with each others' help. This type of nutrition is called symbiotic nutrition.

         Some fungi grow around the roots of some other plants. These plants supply nutrients to the fungi and in turn, fungi supply minerals and water to the plants. Some fungi and algae live together. The fungi provides water, minerals as well as shelter to algae. In return, the algae provide food to the fungi . Lichen is an example o a symbiosis between algae and fungi.

Heterotrophic Plants : Heterotrophic plants do not contain chlorophyll. How do the heterotrophic plants live ? From where do they get food ? Have you seen a yellow, wire-like, leafless climber plants growing on a big tree ? What is its name ? The plants that grow on the body of other plants to obtain food are called as parasitic plants, for example, locant's, Cucuta, etc. Due to the absence of chlorophyll, the Cucuta is completely dependent on the host plants. Hence, it is said to be a completely parasitic plant. You must have also noticed loran thus that grows on trees. 

Q. Which part of the loran thus plant carries out photosynthesis ?

A. Loran thus is a stem-partial parasite. It grows on trees like Mango. Plant absorbs nutrition (minerals and water) from host plant through Haustoria (Sucking roots) which goes up to vascular tissue of the host plants. Aerial part of the Loran thus bear green leaves and capable of photosynthesis.

Insectivorous PLANTS : We have seen how some plants feed upon insects to obtain nutrients . These insectivorous plants generally grow in soil or water deficient in nitrogen compounds. The plants body of the Drosera burmanii has a flower-like appearance. It grows close to the ground. Its leaves are attractively pink or red in colour with hairs at the margin. Droplets of a sticky Subtance found at the tips of the hairs attract insects. The scientist Johannes Burman identified  this plants in Sri Lanka in 1737. Hence, the plants is named after him.

 Q. Why does the pitcher plant feed on insects even thought it produces food by photosynthesis ?

A.  The pitcher plants grow in a place where the soil has a deficiency of nitrogen compounds so to fulfil the need of nitrogen they feed on insects. 

Saprophytic plants : Plants which obtain the food from dead and decaying bodies of other organisms are called saprophytic plants. Various types of fungi like mushrooms and yeast are saprophytes. Fungi secrete digestive enzymes on the dead remain to digest or breakdown the carbon compounds they contain. The resulting solution is absorbed to obtain nutrients. 

Always Remember .... Food gets spoiled due to some fungi. Some fungi cause diseases or illness while some fungi have medicinal properties. Yeast and some mushrooms are useful. Yeast is used in fermentation processes and for making bread. Mushrooms are a rich source of iron and vitamins.