Plants with drought history gain survival mechanisms

Plants that suffer drought learn to deal with the stress thanks to their memories of the experience, new research has found, opening doors to the potential for developing many more crops better able to withstand drought, at a time when the effects of climate change become ever clearer in Kenya.

The research, conducted by the University of Nebraska-Lincoln and led by scientist Michael Fromm, shows that, like animals, plants have memories. The researchers compared the reaction of plants that had been previously stressed to those not previously stressed by withholding water, and found the pre-stressed plants bounced back more quickly the next time they were dehydrated. They studied one crop's drought memory for two years. The crop Arabidopsis, which belongs to the Mustard family, was used because it takes only six weeks to grow, has a small genome, and is a standard lab research plant

The experiment was conducted by sending the plant through a cycle of rapid dehydration, Fromm said. Because soil dries out slowly, the plants were studied in petri dishes and put through two-hour drought stresses.

When the plant recovered from water deprivation, only to be faced with it again a short while later, it increased the transcription of certain genes, helping it cope with the dehydration stress. Arabidopsis, for example, displayed a memory time of five days, meaning that after five days of having enough water, it forgets ever experiencing water deprivation.

This type of memory won’t apply for droughts separated by a significant amount of time, Fromm said. Rather, the genes help the plant survive day to day within a single stress.

According to the scientists, it is hard to know which gene is responsible for drought survival, because plant genomes are so complex. Each gene interacts with each other and a change in one gene accompanies a change in many others. “Thousands of genes are involved in the memory,” Fromm said.

The research also confirmed what home gardeners and nursery professionals have often learned through hard experience: transplants do better when water is withheld for a few days to harden them to drought before they're moved.

Fromm said, "The plants 'remember' dehydration stress. It will condition them to survive future drought stress and transplanting. If I was transplanting something, I would deprive it of water for a couple of days, then water overnight, then transplant."

The team is in the process of determining if other plants remember water scarcity the way Arabidopsis does. Camelina, another member of the mustard family, and corn are being tested. They say Arabidopsis and Camelina are global plants. Corn will help the team determine if the original climate of a plant affects its ability to remember drought.

Kenyan scientists now say that this research could provide a basis for identifying why certain crops, indigenious to the drought ravaged areas of Africa survive those harsh conditions. “We have crops like millet, sorghum and cassava flourish the way they do. And in the wake of the very unpredictable weather pattern, we feel we could benefit a lot from this research in order to assist our people,” said Fanuel Sitti from the Kenya Agricultural Research Institute (KARI).

Written by Bob Koigi for African Laughter

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