Question

Give reasons for the following.

Most of the plants in desert forests have thorns.

Answer 1

1. Defense against herbivores: Thorns deter animals from eating fleshy stems or water‑rich tissues. In deserts, foliage and succulent water stores are especially valuable to herbivores, so physical protection reduces loss of water and biomass.
2. Reduced water loss: Many desert plants have leaves reduced to spines or thorns or have thorns instead of broad leaves. This greatly lowers total leaf surface area and therefore transpiration, helping the plant conserve scarce water.
3. Shade and thermal regulation: Dense spines cast tiny shadows on the plant surface and can reflect or diffuse sunlight, lowering surface temperatures and reducing heat stress and evaporation.
4. Boundary‑layer/wind reduction: Spines disrupt wind near the plant surface, slowing air movement and reducing evaporative loss from stems or any remaining leaves.
5. Mutualisms and extra protection: Some thorny species (e.g., certain acacias) have hollow thorns or provide nectar/food that attracts ants; the ants live in/near the thorns and aggressively defend the plant from browsers and competing plants.