Title. It’s just funny to me how cautious I am not to overwater my plants when in soil. But if I cut a piece of a plant and stick it in 100% water it thrives. Wouldn’t the roots being literally underwater be “overwatered” as well?
In: Biology
Plant cells need oxygen to survive.
Regular soil is a relatively high oxygen environment. Pores and air spaces between the soil grains allow oxygen to enter the soil and reach the roots in the quantities that plant cells need.
Pure water is also a relatively high oxygen environment. A glass of water absorbs water from the atmosphere, and that dissolved oxygen can circulate freely to the roots or stem of the plant. This allows the plant cells to live.
Overwatered, muddy soil is often low in oxygen or lacks it entirely. Why? Because water fills the air gaps between the soil particles, preventing oxygen rich air from reaching the roots. But the water itself can’t circulate because all the soil particles block its movement (water is more viscous than air and can’t move as easily through small passages). At the same time, all the various microbes and fungi growing in the wet soil use up oxygen in the water, so none has a chance to get down to the roots anyway. The plant cells in the roots suffocate and die, killing the plant.
In short, it’s not about water, it’s about oxygen. Soil provides oxygen, water provides dissolved oxygen, soggy soil provides no oxygen.
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