Root System — Important Questions

Fusiform

Step 1: Recall the four types of tap root modifications for food storage. Step 2: Conical roots are broad at the base and taper gradually towards the apex — example is carrot. Step 3: Fusiform roots are swollen in the middle and taper towards both ends (like a spindle shape) — example is radish. Step 4: Napiform roots are spherical at the base but taper sharply towards the tip — example is turnip. Step 5: Tuberous roots are thick and fleshy with no definite shape — example is 4 o'clock plant. Radish is swollen in the middle and narrower at both ends, which perfectly describes a fusiform shape.

Absorbing oxygen from air for better gaseous exchange in waterlogged soil

Step 1: Mangrove plants (like Rhizophora) grow in marshy, waterlogged areas where the soil is poorly aerated. Step 2: Since the soil is flooded, normal underground roots cannot get enough oxygen for respiration. Step 3: To solve this problem, some roots grow vertically upward (they are negatively geotropic) into the air. Step 4: The tips of these exposed roots have minute pores through which the roots can absorb oxygen from the atmosphere — these are called pneumatophores or respiratory roots. Step 5: Option A describes velamen in epiphytic orchid roots. Option B describes prop roots or stilt

Cuscuta

Step 1: Haustoria are special sucking roots developed by parasitic plants to extract nutrition from a host plant. Step 2: These roots penetrate the living host plant and tap into the phloem to suck food (organic nutrients). Step 3: Cuscuta (also called dodder) is a well-known example of a parasitic plant that has haustoria — it appears as orange or yellow thread-like structures growing over its host. Step 4: Vanda (an orchid) has epiphytic roots with velamen tissue that absorb atmospheric moisture — it is an epiphyte, not a parasite. Step 5: Tinospora has assimilatory roots that turn green for

Casparian strips

Step 1: In the cross-section of a dicot root, identify the endodermis — it is the innermost layer of the cortex, made of barrel-shaped closely packed cells. Step 2: These endodermal cells have a special feature — band-like thickenings on their radial (side) walls. These are called Casparian strips. Step 3: Casparian strips are made of suberin and lignin, which make the cell walls impermeable. They control the movement of water and dissolved minerals entering the stele. Step 4: Passage cells are the endodermal cells that LACK casparian strips (found opposite the protoxylem) — they allow water t