Structure of Plants: Root, Stem, Leaf and Flower
Structure of Plants: Root, Stem, Leaf and Flower
Plant structure gives 2 questions in the Part-III paper. The examiner asks parts with their functions, and the flower is the part asked most often because it links forward to reproduction. Learn each structure by what it does, not by its position.
Root and Stem
| Part | Types | Main functions |
|---|---|---|
| Root | Tap root, fibrous root | Anchorage, absorption of water and minerals |
| Stem | Herbaceous, woody | Support, transport, sometimes storage |
- Tap root has one main root with branches — mustard, carrot, radish, gram.
- Fibrous root has many similar roots from the base — wheat, maize, grass.
- Roots that store food: carrot, radish, beetroot and sweet potato.
- Stems that store food: potato, ginger and turmeric — these are underground stems, not roots.
The potato is a stem, not a root, and the sweet potato is a root. This pair is asked deliberately because both grow underground and look similar.
✗ Potato and sweet potato are both modified roots | ✓ Potato is a modified stem; sweet potato is a modified root
The Leaf
The leaf is the food factory of the plant. Its broad, flat blade maximises the surface exposed to light.
- Stomata are tiny pores, mainly on the lower surface, for gas exchange and transpiration.
- Each stoma is bounded by two guard cells that open and close it.
- Venation is the arrangement of veins — reticulate in dicots, parallel in monocots.
- Reticulate venation goes with tap roots; parallel venation goes with fibrous roots.
That last pairing is worth holding on to, because one observation lets you predict the other and questions often supply one and ask for the other.
Transpiration is the loss of water vapour through stomata. It cools the plant and helps pull water up from the roots, which is why it is sometimes called a necessary evil.
The Flower and Its Parts
| Part | Position | Function |
|---|---|---|
| Sepal | Outermost whorl | Protects the bud |
| Petal | Second whorl | Attracts pollinators |
| Stamen | Male part | Anther makes pollen; filament supports it |
| Pistil or carpel | Female part | Stigma, style and ovary; ovary holds ovules |
A flower with both stamen and pistil is bisexual, as in mustard and hibiscus. One with only one of them is unisexual, as in papaya, maize and cucumber. This classification is asked with examples attached.
After fertilisation the ovary becomes the fruit and the ovule becomes the seed. Those two conversions are the single most repeated fact in plant biology, and reversing them is the standard wrong option.
आलू और अदरक तने हैं, शकरकंद जड़ है।
TRE pointer: Three items repeat: the potato is a stem pair, the venation-and-root-type link, and the ovary becomes fruit, ovule becomes seed conversion. All three are single-line facts with a ready-made wrong option. Since you will teach this content to class 6 and 7, expect a question framed around a classroom observation, such as identifying a plant from its venation. With −1/3 negative marking, these are cheap marks to secure.
60-Second Recap
- Tap root in dicots with reticulate venation; fibrous root in monocots with parallel venation.
- Potato, ginger and turmeric are modified stems; carrot, radish and sweet potato are roots.
- Stomata with guard cells sit mainly on the lower leaf surface.
- Transpiration loses water vapour, cools the plant and pulls water up.
- Sepal protects, petal attracts, stamen is male, pistil is female.
- Ovary becomes the fruit and ovule becomes the seed after fertilisation.
Frequently Asked Questions
Is a potato a root or a stem?
A potato is a modified underground stem, which is why it has eyes that sprout into new shoots. A sweet potato, despite the similar name and appearance, is a modified root. Examiners place the two together precisely because both grow underground.
What is the link between venation and root type?
Plants with reticulate or net-like venation usually have tap roots and are dicots, while plants with parallel venation usually have fibrous roots and are monocots. Observing one lets you predict the other, and questions often give one feature and ask for the other.
What does the ovary become after fertilisation?
The ovary develops into the fruit and the ovules inside it become the seeds. Reversing these two is the standard error, and both versions are offered among the options. It is the single most frequently asked fact in the plant reproduction section.
Why are stomata mostly on the lower surface of a leaf?
Because the lower surface is shaded and cooler, which reduces the water lost during gas exchange. Stomata must open to let carbon dioxide in and oxygen out, and placing them away from direct sunlight limits excessive transpiration while still allowing that exchange.