Hold a leaf up to the light and you will see a pattern of lines running through it. These lines are veins. They carry water and minerals into the leaf and carry food out of it. The pattern of veins is called venation, and there are two main kinds. In reticulate venation the veins form a net-like pattern on both sides of a thick central midrib, as in mango, peepal, hibiscus, rose, neem and tulsi. In parallel venation the veins run side by side in straight lines from the base to the tip, as in grass, wheat, rice, maize, banana, sugarcane and bamboo. The flat green part of the leaf is the lamina, and the stalk that joins it to the stem is the petiole. Leaves make food by photosynthesis using sunlight, water and carbon dioxide, and they release water vapour through tiny pores in a process called transpiration.
Now pull up a small weed and a grass plant and compare their roots. Plants have two main root systems. A taproot system has one main thick root growing straight down with thinner side roots called lateral roots. Carrot, radish, mustard, mango, bean, gram and neem have taproots. A fibrous root system has many thin roots of similar size spreading out from the base of the stem like a bunch of threads. Grass, wheat, rice, maize, onion and sugarcane have fibrous roots. Roots anchor the plant in the soil and absorb water and minerals. Here is a wonderful pattern that scientists noticed: plants with reticulate venation almost always have taproots, and plants with parallel venation almost always have fibrous roots. So by looking at a leaf, you can predict the roots without digging. Fibrous roots also hold soil together, which is why grass is planted on slopes to stop soil erosion.
Example: Collect five leaves from different plants, such as mango, grass, hibiscus, banana and a bean plant. Place each leaf under a sheet of thin paper and rub gently with the side of a pencil to make a leaf rubbing that shows the veins. Label each rubbing as reticulate or parallel. Then, for any plant you are allowed to uproot, such as a grass clump and a small weed, wash the roots and sketch them. Expected result: the mango, hibiscus and bean show net-like veins and the weed has a taproot, while grass and banana show parallel veins and the grass clump has fibrous roots.