Back to: Botany 300 Level
Hello, my brilliant Afrilearn scholar! I hope you’re doing great today! Have you ever noticed how some plants shrivel up during the dry season, while others seem to thrive even in harsh desert conditions? Or how some plants struggle to grow in salty water, while others like mangroves flourish in coastal areas? Just like humans, plants have ways of coping with environmental stress. Today, we’re going to learn about how plants respond to drought, salinity, and extreme temperatures—some of the biggest challenges they face in nature.
Physiological responses to drought, salinity, and temperature extremes
Plants vs. Environmental Stress: Who Wins?
Plants, just like people, need the right conditions to survive. Too much or too little water, extreme heat or cold, and high salt levels can stress plants and even kill them. But nature is amazing! Over time, plants have developed physiological responses—special tricks that help them adapt and survive. Let’s break it down into three major stress factors.
1. Drought Stress: How Plants Survive with Little Water
Drought happens when there is not enough water in the soil for plants to absorb. This is common in places like northern Nigeria, where rainfall is low, and in the dry season when rivers shrink. Without water, plants struggle to make food through photosynthesis, and their cells start drying out.
How Plants Respond to Drought
Closing Stomata – Stomata are tiny openings on leaves that let out water vapour. During drought, plants close their stomata to prevent water loss.
Deep Roots – Some plants, like the baobab tree, grow deep roots to reach underground water sources.
Leaf Modifications – Some plants have small, waxy, or hairy leaves to reduce water loss. The cactus, for example, has spines instead of leaves!
Water Storage – Plants like succulents store water in their thick stems or leaves to use during dry periods.
Examples of Drought-Tolerant Plants
Baobab Tree – Stores water in its trunk.
Cactus – Reduces water loss by having spines instead of leaves.
Sorghum & Millet – Common drought-resistant crops grown in Nigeria.
2. Salinity Stress: How Plants Survive in Salty Environments
Salinity stress occurs when plants take in too much salt from the soil or water. This is a big problem in coastal areas like the Niger Delta, where seawater can mix with freshwater, making it too salty for most plants. Salt can damage plant cells, making it hard for them to absorb water.
How Plants Respond to Salinity Stress
Excreting Salt – Some plants, like mangroves, have special glands that remove excess salt from their leaves.
Salt Storage in Vacuoles – Some plants store salt in special compartments inside their cells to keep the rest of the plant safe.
Selective Absorption – Some plants absorb only the water and leave out the salt.
Examples of Salt-Tolerant Plants
Mangroves – Grow in coastal areas and filter out salt from seawater.
Rice – Some varieties of rice can tolerate slightly salty water.
Atriplex (Saltbush) – Stores salt in its leaves to prevent damage.
3. Temperature Stress: Coping with Extreme Heat and Cold
Plants are also affected by very hot or very cold temperatures. Extreme heat can cause water loss and damage plant proteins, while extreme cold can freeze plant cells, stopping them from functioning.
How Plants Respond to Heat Stress
Producing Heat Shock Proteins – These special proteins protect plant cells from heat damage.
Increasing Leaf Surface Area – Some plants spread out their leaves to allow heat to escape.
Developing Waxy Coatings – Some plants have thick, waxy leaves to reduce heat stress and water loss.
Examples of Heat-Tolerant Plants
Date Palm – Grows in the hot deserts of northern Nigeria.
Desert Rose – Stores water and has a waxy coating to survive in high temperatures.
How Plants Respond to Cold Stress
Producing Antifreeze Proteins – These proteins stop ice from forming inside the plant.
Dormancy – Some plants shed their leaves in winter and wait for warmer conditions.
Changing Cell Membranes – Some plants adjust their cell structures to prevent freezing.
Examples of Cold-Tolerant Plants
Pine Trees – Stay green even in freezing weather.
Cabbage – Can survive in colder regions of Nigeria.
Summary
Plants are incredibly resilient and have developed different ways to survive environmental stress. Their physiological responses include:
Drought Resistance – Closing stomata, deep roots, water storage (e.g., baobab, cactus).
Salinity Tolerance – Excreting salt, storing salt safely, absorbing only water (e.g., mangroves, saltbush).
Temperature Adaptation – Producing heat/cold resistance proteins, changing cell structure, dormancy (e.g., date palms, pine trees).
Understanding these responses helps us develop better farming techniques and grow crops in challenging environments.
Evaluation
- What are three ways plants respond to drought stress?
- How do mangroves survive in salty environments?
- Why do some plants have small or waxy leaves in hot climates?
- What role do antifreeze proteins play in plant survival?
- Give two examples of plants that can tolerate extreme temperatures.
You’re doing an amazing job! Now you know how plants fight against drought, salinity, and temperature stress. Keep learning, stay curious, and see you in the next exciting Afrilearn lesson!
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