Back to: Botany 400 Level
My ever-curious Afrilearn legend! How you dey? You’ve been learning like real agbami (star) lately! Today, we go gist about something wey everybody don see before, but no too reason: why leaves turn yellow and fall. That process wey we dey call leaf senescence. And guess what? Na hormones dey control am sharply. Just like how your body dey change when you grow, leaves too dey “retire” gracefully when their job is done — and na correct hormones dey guide the whole process.
Leaf senescence and hormonal regulation
Think about mango tree during dry season. You go notice say some of the green leaves go begin turn yellow, then brown, and finally drop. That no be sickness — na senescence, the natural ageing and controlled death of the leaf. It’s like retirement after years of service. But it no dey happen anyhow; plant hormones like ethylene, abscisic acid (ABA) and cytokinins dey play key role in this process — like oga wey dey issue retirement letter for office. Let’s break it down like well-pounded yam!
What is Leaf Senescence?
Leaf senescence na natural process wey happen when a leaf don old, or when plant dey respond to stress (like drought, nutrient shortage or darkness).
During this time, the plant go start to withdraw useful materials (like nitrogen and sugars) from the leaf and send them to younger parts (like new leaves or fruits).
The leaf go begin change colour — from green to yellow to brown — and then finally drop off.
This process helps the plant conserve energy, survive tough conditions, and support reproduction.
Hormonal Regulation of Leaf Senescence
Ethylene – The Retirement Officer
Ethylene dey trigger and speed up leaf senescence.
It tells the leaf, “Oya, your time don reach. Begin pack your load.”
Especially active when plant dey stressed or preparing for seasonal changes.
Abscisic Acid (ABA) – The Stress Alert
ABA increases when plant dey under drought or cold.
It helps close stomata, save water, and promote senescence to reduce load.
Think of ABA as the voice saying, “We no fit carry everybody — some leaves must go!”
Cytokinins – The Youth Preservers
These ones dey delay senescence.
They promote cell division and chlorophyll maintenance.
If a leaf still dey receive cytokinins from the plant (especially from roots), e go stay green longer.
It’s like say they dey tell the leaf, “You still get work — no retire yet!”
Let’s say you get a maize plant wey dey short of water. The lower leaves go first turn yellow and fall. That maize don send ABA and ethylene to tell those leaves, “Time to go.” But the fresh, upper leaves still dey receive cytokinins and nutrients, so dem stay green — na proper energy management!
Summary
Leaf senescence is the natural ageing and dropping of leaves.
It helps plants recycle nutrients and cope with stress.
Ethylene and ABA promote senescence, while cytokinins delay it.
Hormonal signals help the plant decide which leaves to keep and which to release.
Evaluation
- What is leaf senescence and why is it important?
- Name two hormones that promote leaf senescence.
- What role do cytokinins play in this process?
- How do plants benefit from shedding old leaves?
As you dey learn these things, just dey imagine how many farms, gardens, or research labs go benefit from your brain one day. With this kind of understanding, na only progress full your way. Keep up the fire! Afrilearn dey your corner always, and the next lesson? You go love am!
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