Plants have several smart ways to respond and adapt to drought conditions to survive with limited water. These responses can be structural, physiological, and biochemical. Here’s how they cope:
1. Closing of Stomata:
During drought, plants close their stomata (tiny pores on leaves) to reduce water loss through transpiration. However, this also limits carbon dioxide intake, slowing photosynthesis.
2. Reduced Leaf Area:
Plants may produce smaller leaves or shed older leaves to minimize the surface area exposed to sunlight and air, reducing water loss.
3. Development of Deep or Extensive Roots:
To access water deep underground, plants grow long taproots or spread their roots widely. For example, desert plants like mesquite have roots that reach deep into the soil.
4. Leaf Modifications:
Some plants develop thick, waxy cuticles, leaf hairs, or rolled leaves to reduce evaporation. Succulent plants (like cacti) store water in fleshy stems or leaves.
5. Osmotic Adjustment:
Plants accumulate osmolytes (like proline, sugars, and glycine betaine) inside their cells. These compounds help retain water and maintain cell structure even under dehydration.
6. Reduced Growth Rate:
Plants slow down growth to conserve energy and water, focusing resources on survival instead of producing new tissues.
7. Production of Stress Hormones:
Drought triggers the production of the hormone abscisic acid (ABA), which signals stomata to close and activates drought-response genes.
8. Leaf Wilting and Rolling:
Leaves wilt or curl inward to reduce the surface area exposed to the sun, lowering transpiration rates.
9. Photosynthesis Adjustment:
Some plants use CAM (Crassulacean Acid Metabolism) or C₄ photosynthesis, allowing them to fix carbon efficiently with minimal water loss. CAM plants open their stomata only at night.
10. Seed Dormancy:
In severe drought, some plants allow their above-ground parts to die, while seeds remain dormant until water becomes available again.
In summary:
Plants survive drought by reducing water loss, storing water, improving root efficiency, and changing their physiology and metabolism. These adaptations allow them to endure long dry periods until rainfall returns.