Prakriti is so excited about her new mint plant that she waters it five times a day, keeping the…
Prakriti is so excited about her new mint plant that she waters it five times a day, keeping the soil in the pot soaking wet all the time. She says more water can only help, because plants need water to make food. Her neighbour Ruhi warns that the roots could die this way. Who is right?
Who do you think is right? Pick one.
The answer: Ruhi is right, roots need air in the soil to respire
Why
Prakriti is correct that plants need water — for photosynthesis and to stay firm — and a plant left dry will wilt. But roots are living parts too, and like every living cell they respire: they need oxygen to release energy from food. Roots get that oxygen from the tiny air spaces between soil particles. When the soil is kept soaking wet all the time, water fills those spaces and pushes the air out. The roots can't respire properly, they weaken and begin to rot, and the plant droops — strangely looking thirsty while standing in water. That is why pots have a drainage hole at the bottom, and why gardeners water when the top of the soil feels dry. Test: lift a pot that has been waterlogged for days and smell the soil — a sour, rotten smell and brown, mushy roots are the signs of roots that couldn't get air. Ruhi is right: keeping the soil soaked drives out the air that roots need for respiration, which can kill them.
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