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CBSE Class 06
Science Revision Notes
CHAPTER – 7 Getting toknow Plants Plants areusually grouped intoherbs, shrubs, trees, creepers and climbers. From where does a plant come? A plant comes from a seed. A seed is covered with seed coats., The seedcoats protect theseed. The seed hasa baby plantinside. The babyplant has atiny root towards the outer side. The tiny rootis termed asradicle. The baby plant has a tinyshoot towards theinner side. Thetiny shoot istermed as plumule. Classification ofPlants on theof Growth Habit: (a) Herbs: Have soft, green and weak stems. Example: rice, wheat, maize, sunflower, mint, etc. (b) Shrubs: They are bushy and have hard stems that do not bend easily. These are plants with the stem branching out near the base. Example: lemon, China rose, jasmine, Nerium, etc. (c) Trees: These are big plants which have a tall and strong stem (trunk). Stems have branches in the upper part, much above the ground. Live for many years. Example: mango, neem, banyan, coconut, etc. (d) Climbers: Have weakstems and cannot stand erect. Theytake the support of other treesand climb onthem. Example: pea,grape, vine, etc. (e) Creepers: Plants which creep on the ground and spread out.Example: pumpkin and watermelon. Classification ofplants on thebasis of their Life Cycle:
(a) Annuals: Plants whose life cycle is completed in the one season. These are generally herbs. Example: wheat and mustard. (b) Biennials: Plants whoselife cycle requires two seasons forcompletion. They aregenerally herbs andrarely shrubs. Example: carrot, radish, andpotato. (c) Perennials: Plants whose lifecycle runs formore than twoseasons example: guava, Babul, and palmtrees. Parts ofa Plants: (a) Rootsystem: The rootand its branches make up theroot system ofa plant. Root is theunderground art ofa plant body.It is non-green. The rootgrows into thesoil and awayfrom the light. (i) TapRoot: It is formed by the babyroot (radicle) whichcomes out froma germinating seed. It is themain primary rootarises from thelower end ofthe stem. A number of tiny branches called secondary roots. Example: mustard, neem, rose, etc. Functions of root system: (i) Roots absorb waterand nutrients fromthe soil. (ii) Roots help theplant to standerect. (iii) Roots check soilerosion. (iv) Roots store food. (v) Prop roots offerextra support. MODIFIED ROOTS: Roots mayshow certain changes in their shape, size or structure for performing special functions. These roots are called themodified root. 1. Roots modified for the storage of food: - We findsuch roots incarrots, radish, turnip, (ii) Fibrous Root: A bunch of roots arises from the baseof the stem.Example: wheat, maize, etc.
The stem, The leaves, The buds, The branches, The flower, The fruits, The seeds. beetroot, sweet potato and someother plants. 2. Roots modified to provide support to the plant: - In a banyan tree, you might have noted rootlike roots coming out from thebranches and hanging downwards. These rootsgive support tothe branches. Theyare called thesupporting roots orthe prop roots. 3. Root modified to bear nodules; - On the rootsof the gramand other pulses Rhizobium, anitrogen-fixing bacteria makesits home inthe form of small swellings. These swellings are termed as nodules. (b) Shootsystem: The partof the plant which grows abovethe soil. It includes (ii) Leaf:A leaf is a flat andgreen structure ona plant, coming out from a node onthe stem andalways bearing abud in itsaxil. Parts ofleaf: (a) Petiole: Stalk ofthe leaf withwhich it joined to the stem. (b) Leaf lamina: The flat green portion of theleaf. (c) Veins: These arethe network ofsmall, narrow, tube-like structures on bothsides of themidrib present inthe middle ofthe leaf. The function of Leaf: (i) Transpiration:Process of losing water by theleaves of a plant. (ii) Preparation of foodby the process of photosynthesis. (iii) Flower: It is thereproductive organ ofthe plant.
The function of Flowers: (i) Help inreproduction. (ii) These become fruits that store food and seeds. (iii) Modified flowers like cauliflower, broccoli are rich sources of vitamins. · Parts of Flower: (i) Pedicel: Stalk ofthe flower through which the flower is joined tothe branch. Ithas joined tothe branch. (ii) Sepal: Small green leaf-like structures onthe thalamus. Theyprotect the flower. (iii) Petals: Brightly colored leaf-like structures present inside the sepals. Petals attract theinsects and helpin the process of reproduction. (iv) Stamens: These are long, thin and needle-like structures. These are male organs of the flower. Itconsists of twoparts: Anther, Filament. (a) Anther: The swollen tip of eachstamen that encloses in it a small powdery substance called pollen grains. (b) Filament: Long stalk-like structure that joinsthe anther withthalamus. (v) Carpel: It is a flask-shaped organ in thecenter of theflower. It isthe female organ of the flower. It consists three parts: Style, Stigma, and Ovary. (a) Style: a Long thin tube-like structure which isswollen at thebase. (b) Stigma: Small, roundand sticky partof the carpel at the topof the stylethe traps thepollen grains. (c) Ovary: Swollen partof carpel thatcontains ovules. The Bud: A budis a compact or a condensed shoot. It encloses future stem, nodesand leaves. Axillary bud Terminal bud floral bud
(i) Stem:Stemforms the central axis of theplant body.Gives riseto a number of branches that bear leaves. Thestem bears leaves, flowers, and fruits. The function of Stem: (i) It provides support to plant. (ii) It bears important plant parts. (iii) It helps intransportation of water and food. (iv) Underground stems store food. (v) Thick and fleshy stems make food. (vi) Stem modified intotendrils give extrasupport for plants. Some ExtraPoints: The pattern of veins on the leaf is called venation. It can be reticulate or parallel. Leaves giveout water vaporthrough the process of transpiration. Green leaves make their foodby the process of photosynthesis using carbon dioxide andwater in thepresence of sunlight. Roots absorb water and minerals from the soiland anchor theplant firmly in the soil. Roots are mainly of two types: taproot and fibrous roots. Plants having leaves with reticulate venation have tap roots while plants having leaves with parallel venation have fibrous roots. The stem conducts water from rootsto the leaves (and other parts) and food from leaves toother parts of the plant.
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