Herbs – Plants with green and tender stems almost no branches. E.g: Tomato – Herb
Shrubs – Branches near the base, thin but hard stem. E.g: Lemon- shrub
Tree- Thick, brown stems. Tall with branches near the top. Mango – Tree. Branchy part of the tree above the stem is called crown. Crowns of tall trees form a roof like structure called Canopy. Crowns of smaller trees form a lower layer called Under-storey.
Creepers-plants with weak stems that spread on ground or take support of other structures. [Money plants, beanstalk, gourd, grape vines]
Stem – conducts water and minerals.
The part of a leaf by which it is attached to the stem - petiole.
The broad, green part of the leaf - lamina
Veins – lines present on the leaf. Thick line in middle is midrib.
Design of veins – venation is of two types reticulate – net like or parallel.
Transpiration – Leaves releasing water in the form of water vapor. The evaporation of water from leaves creates a suction that pulls water from roots to greater height. It also cools the plant.
Xylem is the tissue in plants for transportation of water and minerals. Food is transported by a second tissue called phloem. Xylem is made of trachids, vessels, parenchyma and fibers. Unidirectional movement is possible.
Phloem is also a complex permanent tissue like xylem and consists of sieve tubes, companion cells, parenchyma and fibers. Transport food in both directions.
Photosynthesis
– Leaves prepare food using carbon dioxide and water
and food produced is stored in form of starch. Oxygen is
released in this process. Amount of oxygen released during
photosynthesis is much higher than the CO2 that is
released during night time.
The following things occur in photosynthesis, absorption of light energy by chlorophyll, conversion of light energy into chemical energy and splitting of water molecules into hydrogen and oxygen. Reduction of CO2 into carbohydrates. These steps need not occur immediately.
Leaves take in CO2 from atmosphere through pores present on surface called stomata; these are surrounded by guard cells. Leaves have a green pigment called chlorophyll that captures energy from the sun and uses it to synthesize food using water and CO2. Roots also take in air from the soil.
Cuscuta is a parasitic plant that takes nutrition from other host plants. Pitcher plant is insectivorous plant but it also carries out photosynthesis. These plant doesn’t get sufficient nutrition from the soil.
Fungi like yeast, Mushrooms are saprotrophs that feed on decaying matter.
Symbiotic relationship: Some organisms live together and share food and nutrients. [Lichens – Algae and fungus live together. Algae provide food by photosynthesis and fungi provide water, nutrients and shelter. They are good indicators of pollution as they don’t grow in polluted areas. ]
[Rhizobium
a bacteria converts atmospheric nitrogen into
soluble form; this is absorbed by the leguminous plants
that in turn provide it shelter and food. Thus nitrogenous
fertilizers are not needed for leguminous plants. ]
Mycorrhizal
fungi – Phosphorous fixing fungi lives in the roots
of higher plants.
Frankia – nitrogen fixer bacteria for non leguminous plants.
Blue green algae, nostoc, azotobacter and Lightning are also nitrogen fixers. Ammonia is converted to nitrites by nitro somas and nitrococcus. This is converted to nitrate by nitrobacteria.
Nitrate poisoning of ground water causes methaemoglobina [blue baby syndrome].
Roots- absorb water and nutrients from soil by a process called osmosis. They anchor the plant to the soil. Root hairs increase surface area for absorption.
Root types are tapped root [a main root and lateral root] or fibrous roots [hair like roots]. Some plants like banyan, grass roots arise from parts other than radicle called adventitious roots.
Plants with tap roots have reticulate venation and with fibrous roots have parallel venation system.
Edible roots - carrot, radish, sweet potato, turnip and tapioca.
Roots, stems, leaves are vegetative parts of plants and flowers are reproductive parts of plants.
Two types of tissues in plants – permanent [non-growing] and meristematic [growing]. Depending on their location they are apical, intercalary or lateral. Initially meristems grow cells same as themselves but as these cells grow and mature they get differentiated into components of other tissues. Meristem cells have dense cytoplasm, no vacuoles, thin cell walls and large nuclei.
Permanent tissue is of multiple types like
Parenchyma – these are living tissues which store food and provide support to plants. They may contain chlorophyll and then it’s called chlorenchyma. In floating plants it has air in the intercellular space and is responsible for buoyancy and called aerenchyma.
Collenchymas are living tissue which provides mechanical support to plant and also flexibility without breaking.
Sclerenchyma is dead tissue but hard and no intercellular space. It provides mechanical support to plant. Cell walls are thick due to lignin. Epidermis is the single, continuous layer of cells that covers entire plant body. It has pores called stomata at certain in points that allow gaseous exchange. Epidermis is thicker in plants in deserts to prevent water loss.
Macronutrients: These are present in plant tissue in large number; some are obtained from water [H, O], from air [C] and rest from soil [N, P, K, Ca, Mg, and S]. Useful as components of biomolecules, activate/inhibit enzymes, components of energy related substance, affect osmotic potential of cell,
Micronutrients: Needed in small amounts. These include iron, manganese, copper, molybdenum, zinc, boron, chlorine and nickel.
Deficiency of N, K, and Mg are visible in senescent leaves as biomolecules with these elements are broken down to mobilize younger leaves. Boron and calcium deficiency leads to death of meristem, buds and tips. Phosphorous deficiency [blue leaves] and Fe, Mn, Mg, N deficiency [yellow leaves].
Green manures – cover crop that is planted on the field and ploughed under while its green. This is done to improve nutrients in the soil.
Legumes [N2 fixers] – cowpea, soybean,
Non legumes [add biomass, suppress weeds] – sorghum, millets, sudan grass, buckwheat
Cocaine is obtained from coca plant. Charas, ganja, hashish, and marijuana are obtained from cannabis. Opium, morphine, thebaine and heroin are obtained from poppy plant.
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