Diversity and Functions of Plant Parts PDF

3 Diversity and Functions of Plant Parts Plants in our environment show an enormous diversity as animals. Observe the diversity of plants in the forest shown in Figure 3.1. Figure 3.1 A rain forest The major reason for the beauty and the wonder o...

3 Diversity and Functions of Plant Parts Plants in our environment show an enormous diversity as animals. Observe the diversity of plants in the forest shown in Figure 3.1. Figure 3.1 A rain forest The major reason for the beauty and the wonder of a forest is the diversity of plants. Plants differ each other in its size and morphological features. The reason for this vast diversity is the adaptations of plants to survive in different environments. You have already learnt the parts of a plant in grade 7. Recall what you have learnt and engage in Activity 3.1 to study further about the parts of a plant. Activity 3.1 You will need : - 'Kuppameniya'/'kuppaimani' or a 'monarakudumbiya'/ 'seethaviyar selugkaluner' plant. Method : - ² Uproot the plant from the soil without damaging the root system, and wash properly. ² Observe the plant and identify its parts. ² Draw a diagram and name the parts. 24 Science | Diversity and Functions of Plant Parts Figure 3.2 shows the main parts of a plant. Flowers Compare your diagram with the given figure. Fruits Shoot Every flowering plant consists system of fruits, leaves, stem and roots. But they do not appear same Leaves in every plant. They have an extensive diversity. Let us have Stem a review about the diversity and Tap root the functions of leaves, stem and roots of a plant. Root system Lateral roots Figure 3.2 Parts of a plant 3.1 Diversity and functions of plant leaves Leaves are considered as the most significant part of a plant. Most of the leaves are green in colour. The main function of a leaf is photosynthesis. Food is produced in plants having chlorophyll by using carbon dioxide, water and solar energy. This process is known as photosynthesis. Plant leaves are well adapted for efficient photosynthesis. Let us do Activity 3.2 to study about this. Activity 3.2 You will need : - Some leaves of jak, mango, temple flower and manioc Method : - ² Observe the leaves well. ² Compare the thickness of the leaves. ² Draw the area of the leaves on a square ruled Figure 3.3 sheet and compare them. Science | Diversity and Functions of Plant Parts 25  For the purpose of photosynthesis a leaf is typically flat and thin to expose to light over a broad area and allow light to penetrate fully into the tissues. Thick and fleshy leaves can also be seen as an adaptation to adverse (arid) environmental conditions. e.g:- Aloe, temple flower, yellow oleander (kaneru) Figure 3.4 shows the parts of a leaf. Veins Base Tip Margin Petiole/ leaf stalk Lamina/blade Figure 3.4 Parts of a leaf Does every leaf have the same shape of petiole, margin, base and tip? Do Activity 3.3 to study about it. Activity 3.3 You will need : - Some leaves that can be found in your environment (e.g: mango, papaw, rose, temple tress, 'Bo leaf'/zarasa illaiZ) Method: - ² Obtain leaves from different plants in your environment. ² Observe the leaves and draw pictures having different blades, bases, margins and tips. When you observe the blades of these leaves you will understand that they have different shapes (Figure 3.5). 'Gotukola'/ 'Kottamba' / ʻVallaraiʼ ʻKottankachchiʼ Radish Mango 'Kohila'/ ʻKohilaiʼ Figure 3.5 Diversity of leaf blades 26 Science | Diversity and Functions of Plant Parts You would have observed that there is a wide variation in leaf structure. That is due to their adaptations for the main function as well as various other functions. Study the following diagrams and identify further the diversity of leaves. If you observe the tips of those leaves you will notice that the tips are different as sharp, curved, pointed, divided etc (Figure 3.6). 'Niyangala'/ 'Koboleela'/ jak 'Bo' leaf/'Arasa ilai' Temple trees 'Karthikaipoo' 'Thiruvaththi' Figure 3.6 Diversity among leaf tips The margins can be serrate or smooth. (Figure 3.7) Hibiscus/Shoe 'Akkapana' Rose Flower Temple trees Begonia 'Sadaikaraichan' Figure 3.7 Diversity among leaf margins The bases and the petiole of leaves too have different forms (Figure 3.8). 'Kohila' Lotus 'Bo' leaf Shoe flower Temple trees Figure 3.8 Diversity among leaf base When you observe the environment you will be able to study more about other adaptations of leaves. Science | Diversity and Functions of Plant Parts 27  Leaf arrangement The leaves are fixed to the stem in a way to expose all the leaves to the sun light. The pattern of fixing the leaf to the stem of a plant is known as leaf arrangement. Leaf arrangment supports efficient photosynthesis. Some leaf arrangements are given below. ² Leaves are on alternate sides of the ² Leaf attachments paired at nodes and stem. in opposite directions. Figure 3.9 'Anona' ('Katu Anoda')/ 'Annamunna' Figure 3.10 Guava ² Three or more leaves attach at each ² Leaves are attached in a spiral manner node on the stem in a whirl. around the stem. Figure 3.11 'Rukkaththana'/ 'Earlilaippalai' Figure 3.12 'Kanda'/'Vattakkanni' Assignment 3.1 ² Observe the environment and identify the leaf arrangements as much as possible. ² Complete the given table using your observations. Table 3.1 Leaf arrangement Examples of trees Leaves are on alternate sides of the stem. '''''''''''''''''''''''''''''''''''''' Leaf attachments paired at nodes and leaves in opposite '''''''''''''''''''''''''''''''''''''' directions. Three or more leaves attach at each node on the stem in a '''''''''''''''''''''''''''''''''''''' whirl. Leaves are attached in a spiral manner around the stem. '''''''''''''''''''''''''''''''''''''' 28 Science | Diversity and Functions of Plant Parts Let us now consider the other functions of leaves. ² Transpiration is the process of evaporation of water through stomata from plants (Figure 3.13). Transpiration helps to transport water to the upper parts of the plant. The leaves of plants in arid environments, are adapted to minimize transpiration. Stomata Figure 3.13 Internal structure Some adaptations are given below. of a leaf ² Thick, waxy cuticle e.g. - temple trees, oleander ² Leaves reduced to spines e.g. - cactus ² Thin leaves e.g. - 'kasa' / 'savukku' ² Reduced number of leaves e.g. - 'navahandi' / 'kally', 'heerassa'/'pirattai' Temple trees Cactus 'Kasa' Figure 3.14 Adaptations to minimize transpiration ² Some leaves are adapted to store water. They have become fleshy because they have specialized tissues to conserve water (Figure 3.15). 'Akkapana' Aloe Figure 3.15 Plants with water storage leaves Science | Diversity and Functions of Plant Parts 29  ² Some leaves produce new plants through asexual reproduction. e.g. :- 'Akkapana', 'begonia' Let us do Activity 3.4 to study how some plant leaves produce new plants. Activity 3.4 You will need : - some leaves of plants such as akkapana, begonia, peparomia Method : - ² Make a small cut at the veins of the above mentioned leaves and cover the place with soil ² Keep them watering for several days ² After 3-4 days observe the roots near the veins of the leaves. 'Akkapana' Begonia Peparomia Figure 3.16 3.2 Diversity and functions of plant stems The basic functions of a stem are supporting and bearing leaves, buds, flowers, fruits, seeds of the plant and keeping the plant upright. Also the stem transports water and minerals throughout the plant. Most stems are found above the ground. Some stems grow underground and are known as underground stems. In addition to the basic functions, stems have adapted to fulfill other functions. Let us study the diversity of stems based on their adaptations. ² Most stems produce new living tissues allowing plants to grow and reproduce. These stems are known as propagative stems. Given below are some examples for propagative stems (Figure 3.17, 3.18). 'Gotukola' 'Undupiyaliya'/ 'Sirupulladi' 'Ambul ambiliya'/ 'Puliyarai' Figure 3.17 Some plants reproduced by runners/ stolon 30 Science | Diversity and Functions of Plant Parts  Banana 'Kalanduru'/ 'Paalargu' Paddy Figure 3.18 Some plant species re-produced by Suckers ² Some plants store food in aerial stems (Figure 3.19). Sugar cane 'Kithul' Figure 3.19 Some plants with storage stems ² Some underground stems serve the functions of storage of food perennation and sexual propagation. During the adverse seasons the aerial parts get destroyed but the underground stem survives. During favourable seasons new sprouts come out from the underground stem using stored food (Figure 3.20). Turmeric Ginger Onion Potato Figure 3.20 Some plants reproduced by underground stem Science | Diversity and Functions of Plant Parts 31  ² Some stems are green and photosynthetic. Such stems are called photosynthetic stems (Figure 3.21). Cactus 'Daluk' / 'Sathurakkalli' Figure 3.21 Some photosynthetic stems ² Some plants fix to a support to climb up and absorb sun light efficiently. Such stems are called climbing stems (Figure 3.22). 'Venival/ Maramanjal' Beans Figure 3.22 Some plants with climbing stems 32 Science | Diversity and Functions of Plant Parts  Assignment 3.2 ² Complete Table 3.2 using examples for each type of stems which have adapted to carryout the functions given below. Table 3.2 Propagative Aerial stems with Underground Photosynthetic stems food storage stems stems 3.3 Diversity and functions of plant roots The basic function of root is to anchor the plant in the soil, absorb and transport water and minerals. There are some roots which are adapted to satisfy other functions. Other than the tap root and its branches, there are roots which arise from other parts of the plants. These roots are known as adventitious roots. There are roots that adapted to fulfill many other functions. They are given various names. ² Tuberous roots - The roots that are swollen due to storage of food are known as tuberous roots. Some tuberous roots allow the plant to survive in unfavourable seasons. Food can be stored either in the tap root or in adventitious roots. Storage of food in tap root Carrot Radish Beet Figure 3.23 Some plants that store food in tap root Science | Diversity and Functions of Plant Parts 33  Storage of food in adventitious roots Manioc Sweet potato Dahlia Figure 3.24 Some plants that store food in adventitious roots ² Prop roots - Adventitious roots that arise from branches. They penetrate the soil and helps to support branches. Banyan Tree 'Rath kadol '/ 'Sen kandal' Figure 3.25 Some plants with prop roots ² Stilt roots - Adventitious roots arise from the stem, grow below the ground and support the stem. 'Vetakeyya'/'Thalai' 'Rampa' 'Maha kadol'/'Perung kandal' Figure 3.26 Some plants with stilt roots 34 Science | Diversity and Functions of Plant Parts ² Climbing /Clasping roots - Roots that help the climbing stem/ creepers to fix to a surface/support. Betel Pepper Figure 3.27 Some plants with climbing roots ² Aerial roots - These roots absorb moisture from the atmosphere and supply the plant. These specialized roots can be found mostly in epiphytes. Orchid Vanilla Figure 3.28 Some plant with aerial roots ² Respiratory roots - These roots absorb air from the atmosphere and supply to the plant. They are specialized roots which can be found mostly in mangrove plants. Sonneratia 'Maha kadol' Figure 3.29 Some plants with respiratory roots Science | Diversity and Functions of Plant Parts 35  ² Propagative roots - These roots produce new plants. Curry leaves Guava 'Beli/Vilvam' Figure 3.30 Some plants with propagative roots Assignment 3.3 Collect some root specimens and study them. Consider the necessary steps that should be taken to conserve these roots. Assignment 3.4 Plan a field visit to observe the nature and the diversity of plants. Study the adaptations of plants and relate them to their functions. Plants play a vital role in the environment. Therefore, it is your duty to explore and collect specimens with minimum damage to the environment. 36 Science | Diversity and Functions of Plant Parts  Summary ² The major parts of a plant are roots, stem, leaves, fruits and flowers. ² There is vast diversity among parts of the plants. Adaptation of plant parts to their functions is the reason for this vast diversity. There are some plant parts that exhibit special adaptations. ² The basic function of a leaf is photosynthesis. Also some leaves are adapted to store food and water and also for propagation. ² The basic function of a stem is to hold leaves, flowers, fruits and transport water and minerals throughout the plant. ² Some stems are adapted for photosynthesis, to climb up, propagation and to store food. ² The basic function of roots is to anchor the plant in the soil, absorb water and minerals. ² Tuberous roots, prop roots, stilt roots, climbing roots, aerial roots and respiratory roots are adapted for special functions. ² The reason for vast diversity among plants is their functions and adaptations to survive in different environments. Exercise 1) Write the main function of the given plant parts. a) Plant leaves.................................... b) Stem.......................................... c) Roots.......................................... 2) Write the special adaptations of the following plant roots/stems/leaves. i. Cactus v. Sweet potato ix. 'Niyangala' ii. Carrot vi. Pepper x. Orchid iii. Banyan vii. Begonia xi. Guava iv. Aloe viii. 'Navahandi' xii. 'Rampa' Science | Diversity and Functions of Plant Parts 37  3) Fill in the blanks. i) The pattern in which leaves grow on the stem is known as ……………….. ii) Sugar cane, palmyrah are examples for ………………. stems. iii) The leaves of the cactus tree reduced to spines is an adaptation to minimize …………………. iv) Curry Leaves, beli, bread fruit trees often use the ……………………. for propagation. v) Respiratory roots are specialized roots that can be seen in ………...……… plants. Technical Terms Diversity of leaves -- m;%j, úúO;ajh -- Cø»PÎß £ÀÁøPø© Diversity of stems -- l|kaj, úúO;ajh -- uskPÎß £ÀÁøPø© Diverstiy of roots -- uq,aj, úúO;ajh -- ÷ÁºPÎß £ÀÁøPø© Photosynthetic stems -- m%NdixYaf,aIl l|ka -- Cø»zöuõÈÀ uskPÒ Climbing stems -- wdfrdayl l|ka -- HÖ® uskPÒ Propagative stems -- m%pdrK l|ka -- CÚ®ö£¸US® uskPÒ Underground stems -- N+.; l|ka -- {»URÌz uskPÒ Tuberous stems -- wdlka§ l|ka -- QʸÁõÚ uskPÒ Tuberous roots -- wdlka§ uq,a -- QʸÁõÚ÷ÁºPÒ Prop roots -- lre uq,a -- uõ[S®÷ÁºPÒ Stilt roots -- lhsre uq,a -- ªsi÷ÁºPÒ Aerial roots -- jdhj uq,a -- PõØÔØS›¯ ÷ÁºPÒ Respiratory roots -- Yajik uq,a -- ‰a_÷ÁºPÒ Storage roots -- ixÑ; uq,a -- ÷\ª¨¦ ÷ÁºPÒ Propagation -- m%pdrKh -- CÚ¨ö£¸UP® 38 Science | Diversity and Functions of Plant Parts