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Drought: the slow death

Photo credit: TheWestern Producer

In drought conditions, the plant closes its stomata, which when combined with less-than-optimal moisture, causes a drop in the rate of photosynthesis. The plant does not absorb as much solar energy and the chlorophyll breaks down, causing the leaves to yellow. Pigments in the leaves such as carotenoids, which help protect against damage from unused light energy, can also turn the leaves yellow. | File photo

Plants react quickly to survive in dry conditions but not in a way that is good for yield

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For a plant living in a prairie field, death by drought lurks just around the next El Nino

The physiological trauma that occurs within that plant during drought is a bit more complicated than “it just ran out of water and dried up.”

A plant cannot put itself into the “hold mode” for a few extra days waiting for help to arrive in the form of rain, says Dr. David Simbo, crop specialist with the Lakeland Agricultural Research Association in Bonnyville Alta.

A plant cannot think. It doesn’t know whether rain is coming tomorrow or in six weeks. It can only react to the immediate situation, and if that situation is water deprivation, then the dying process automatically begins.

“The plant normally takes in carbon dioxide for photosynthesis through the stomata in the leaves,” explains Simbo.

“But during drought, as a means of reducing water loss, the plant will close the stomata. When that happens, carbon dioxide no longer goes into the leaves. The process of photosynthesis is hampered by the lack of water and the lack of carbon dioxide.

“Chlorophyll, the green pigment in the leaves, starts to break down since it’s not being used. That’s why a plant at the beginning of drought looks yellowish. The green chlorophyll is breaking down. Now, the plant needs every mineral and metabolizing possible to survive.”

Read the full story: The Western Producer

Published by

Willem Van Cotthem

Honorary Professor of Botany, University of Ghent (Belgium). Scientific Consultant for Desertification and Sustainable Development.