What are leaf venation and the types of roots?

Veins and venation

Look closely at a leaf and you will see thin lines running through it. These are veins, and the pattern they make on the leaf is called venation. Holding a leaf against the light makes them easy to see.

• Reticulate venation: a net-like pattern of veins on both sides of a thick middle vein. Hibiscus leaves show it.
• Parallel venation: the veins run parallel to each other. Banana and grass leaves show it.

So leaves give us one more way to group plants.

Two kinds of roots

Do all plants have similar roots? In Activity 2.6, you wet the soil around a few small herbs, loosen it with a khurpi (trowel) and gently dig them out without damaging the roots. After washing and observing the roots, you replant the herbs so they can keep growing.

• Taproot: one main root with small side roots arising from it, as in a mustard plant. Hibiscus has a taproot too.
• Fibrous roots: a bunch of similar-sized thin roots growing from the base of the stem, as in common grass. Other grasses have fibrous roots as well.

Venation and roots go together

In Activity 2.7, you collect saplings of five common plants, for example lemongrass, marigold and sadabahar (periwinkle), and record their venation and roots before planting them in the school garden. A pattern appears:

Plant	Leaf venation	Roots
Lemongrass	Parallel	Fibrous
Sadabahar	Reticulate	Taproot
Chickpea (chana)	Reticulate	Taproot
Wheat	Parallel	Fibrous

Generally, plants with reticulate venation have taproots, and plants with parallel venation have fibrous roots.

Seeds: dicots and monocots

Are all seeds alike? In Activity 2.8, you soak chickpea and maize seeds in water for two or three days and remove the seed coat of a chickpea. The chickpea splits into two parts; each part is a cotyledon. Maize has a single thin cotyledon.

• Plants whose seeds have two cotyledons are dicotyledons, or dicots.
• Plants whose seeds have one cotyledon are monocotyledons, or monocots.

Now the three features line up: dicots have reticulate venation and a taproot system, while monocots have parallel venation and a fibrous root system.

	Dicots	Monocots
Cotyledons in the seed	Two	One
Leaf venation	Reticulate	Parallel
Roots	Taproot	Fibrous
Examples	chickpea, mustard, hibiscus, sadabahar, kidney bean	maize, wheat, grass, lemongrass, banana

Try it yourself

Collect a peepal or mango leaf and a blade of grass or a maize leaf. Hold each against the light: the peepal leaf shows a thick middle vein with a fine net of smaller veins, while the grass blade shows many thin veins running side by side from base to tip. Then gently dig out a small weed and a tuft of grass after watering the soil. Compare their roots, note what you see in your notebook, and replant them.

Using the pattern

Because these features usually go together, one clue tells you about the others. A radish is a thick taproot that stores food, so you can expect net-like veins in its leaves. Wheat grains have one cotyledon, so a wheat plant will have parallel venation and fibrous roots. For herbs, shrubs and trees, see herbs, shrubs and trees; for every textbook question, see the Chapter 2 NCERT solutions.