Plants – Structure and Agriculture
Plants – Structure and Agriculture
Plants – Structure and Agriculture
Key idea: Plants are primary producers. Their body structure (root, stem, leaf, flower, fruit and seed) directly controls agricultural yield and quality.
| Plant Part | Main Function | Importance in Agriculture |
|---|---|---|
| Root system | Anchorage and absorption of water and minerals from soil | Deep and healthy roots help crops withstand drought and wind; better nutrient uptake increases yield |
| Stem | Support and transport of water, minerals and food | Strong stems hold grains, fruits and leaves; lodging (bending) of stems in paddy and wheat reduces yield |
| Leaves | Photosynthesis (food preparation) and transpiration | Broad, healthy leaves increase photosynthesis and finally grain or fruit yield |
| Flower | Reproductive organ forming fruits and seeds | Pollination and fertilisation in flowers decide the number and quality of fruits and seeds |
| Fruit | Protects and helps in dispersal of seeds | Main economic product in many crops like mango, banana, tomato, chilli |
| Seed | New plant formation (germination) | Good quality seeds are first step for high-yield agriculture |
| Cause | Process | Impact / Consequence |
|---|---|---|
| Healthy plant structure with strong roots, stems and leaves | Efficient absorption, transport and photosynthesis | Higher biomass and grain / fruit yield in fields |
| Weak stems and poor root system | Less water and mineral uptake, lodging of plants during wind or rain | Yield loss and poor quality produce even with good soil |
Memory Line: For crops, remember – Root drinks, Stem carries, Leaf cooks, Flower sets, Fruit sells, Seed starts.
Exam Tip: When a question asks “Which plant part directly decides the number of seeds?”, link it to flower and its reproductive structures (ovule and ovary).
Exam Trap: Do not confuse root hairs (part of root) with fungal hyphae. Root hairs are extensions of root cells, not separate organisms.
Plant tissues
Key idea: Plant tissues are groups of similar cells working together. They are broadly divided into meristematic (dividing) and permanent (mature) tissues. Understanding them helps in grasping growth, strength and transport in plants.
| Type of Tissue | Location | Main Function |
|---|---|---|
| Meristematic – Apical meristem | Tips of roots and shoots | Increase in length (primary growth) |
| Meristematic – Lateral meristem (cambium) | Sides of stem and root | Increase in thickness (secondary growth) |
| Meristematic – Intercalary meristem | Base of leaves or internodes (especially in grasses) | Regrowth after grazing and cutting (important in crops like paddy, wheat) |
| Simple permanent – Parenchyma | Soft parts – cortex, pith, mesophyll of leaves | Storage, photosynthesis, filling spaces |
| Simple permanent – Collenchyma | Leaf stalks, below the epidermis of stems | Flexible support in growing parts |
| Simple permanent – Sclerenchyma | Hard parts – shells of nuts, veins of leaves | Mechanical strength (thick, lignified walls) |
| Complex permanent – Xylem | Vascular bundles in roots, stems and leaves | Transport of water and minerals from root to other parts |
| Complex permanent – Phloem | Vascular bundles along with xylem | Transport of prepared food from leaves to all parts |
| Cause | Process | Impact / Consequence |
|---|---|---|
| Active meristematic tissues at tips and sides | Continuous cell division in these regions | Roots and shoots keep growing in length and thickness; important for crop canopy and root spread |
| Well developed xylem and phloem | Efficient transport of water, minerals and food | Healthy growth, uniform grain filling and good quality produce |
Memory Line: “Meri – Grow, Perma – Work” – Meristematic tissues grow, permanent tissues do the work. Xylem = water & minerals, Phloem = food.
Exam Tip: If the question talks about thickening of stem or tree trunk, connect it to lateral meristem / cambium, not apical meristem.
Exam Trap: Parenchyma cells are usually living, but sclerenchyma cells at maturity are dead. Many questions try to interchange these.
Agricultural Practices
Key idea: Agricultural practice is a step-wise sequence from preparing soil to storing grains. Each step has scientific reasons and direct effect on crop yield.
| Stage | What is done | Reason / Outcome |
|---|---|---|
| Preparation of soil | Ploughing, loosening, levelling and adding organic manure | Improves aeration, root penetration and mixes nutrients uniformly |
| Sowing | Placing good quality seeds at proper depth and spacing | Ensures uniform germination and avoids overcrowding |
| Manuring and fertilisation | Adding farmyard manure, compost, green manure or chemical fertilisers (N, P, K) | Replenishes soil nutrients removed by previous crops |
| Irrigation | Supplying water by canals, wells, tube-wells, drip or sprinkler systems | Keeps soil moisture at proper level for crop growth |
| Weeding | Removing unwanted plants by hand, tools or weedicides | Reduces competition for nutrients, water, light and space |
| Protection from pests and diseases | Using resistant varieties, traps, biological control and safe pesticides | Prevents yield loss due to insects, fungi, bacteria and viruses |
| Harvesting | Cutting mature crop using sickle, machines or combines | Prevents shattering or rotting of grains in the field |
| Threshing and winnowing | Separating grains from stalks and chaff | Gives clean grain ready for storage or marketing |
| Storage | Drying grains and keeping them in bags, bins, silos or warehouses | Reduces attack of insects, rats and fungi and maintains quality |
| Cause | Process | Impact / Consequence |
|---|---|---|
| Using certified seeds and proper sowing methods | Selection of disease-free, high-germination seeds and correct spacing | Uniform crop stand and higher plant population per hectare |
| Ignoring weeding and pest control | Weeds and pests compete and damage crop plants | Sharp fall in yield and poor quality grains or vegetables |
Memory Line: Easy order – Prepare → Sow → Nourish → Water → Weed → Protect → Harvest → Store. Questions often test correct sequence.
Exam Tip: For Kharif crops (paddy, maize, cotton, groundnut) remember “Rainy season – June to October”. For Rabi crops (wheat, gram, mustard) remember “Winter season – October to March”.
Exam Trap: Manure and fertiliser are not the same. Manure improves soil structure plus nutrients; fertiliser mainly adds specific nutrients and may harm soil if overused.
Improvement in crop yields
Key idea: Crop yield can be improved by a combination of better seeds, better agronomic practices and better protection. These ideas are core to questions on Green Revolution and modern agriculture.
| Method | Process / Example | Effect on Yield |
|---|---|---|
| High yielding varieties (HYV) | Developed by plant breeding (e.g., improved wheat and rice varieties used in Green Revolution) | More grains per plant, shorter duration crop, better response to irrigation and fertilisers |
| Balanced use of manure and fertilisers | Using organic manure + NPK fertilisers as per soil test | Supplies nutrients without damaging soil health, maintains yield for long time |
| Efficient irrigation | Canal irrigation, tube-wells, drip and sprinkler systems | Reduces water stress and allows cropping even in low rainfall areas |
| Crop rotation | Growing different crops in sequence, such as cereal followed by pulse | Maintains soil fertility, breaks pest and disease cycles, better overall yield |
| Mixed cropping and intercropping | Growing two or more crops together in same field with proper row arrangement | Reduces risk of total crop failure, better use of nutrients and sunlight |
| Integrated pest management (IPM) | Combines resistant varieties, biological control, traps and minimum safe pesticides | Controls pests, protects environment and maintains beneficial insects |
| Use of farm mechanisation | Use of tractors, harvesters, seed drills, sprayers | Saves time and labour; allows quick sowing and harvesting at correct time |
| Improved storage and marketing | Scientific storage in silos, cold storages and fair price marketing | Reduces post-harvest losses and gives better income to farmers |
| Cause | Process | Impact / Consequence |
|---|---|---|
| Adoption of HYV seeds with irrigation and fertilisers | Higher photosynthesis and grain formation per plant | Sharp rise in production (basis of Green Revolution in India) |
| Continuous use of only chemical fertilisers without organic matter | Soil becomes hard and loses structure and microbes | Yield initially increases but later declines, soil becomes “tired” |
Memory Line: Three pillars of yield improvement – Good seed, Good soil, Good care (variety, fertility, management).
Exam Tip: When a question mentions “legume in crop rotation” (pulses, beans, peas), connect it to nitrogen fixation and soil fertility improvement.
Exam Trap: High yielding variety does not mean high yielding without care. It needs more fertiliser, irrigation and management than traditional varieties.