Commercial crops such as grapes, peaches, berries and flower bulbs all become dormant in winter, basically sleeping through seasonal winters before they begin to grow, flower and bear fruit again in warmer months.
Critical attention for commercial farmers is to have good and synchronized tree growth. The problem in mild winter climates is that plants do not receive enough cold, and regrowth becomes widespread with some shoots even failing to grow. When inactive tree gardens begin to grow at about the same time, this usually makes trees and crops easier and cheaper – but tree growth and time are controlled by unpredictable winter weather tricks.
Now a group of scientists from Jazan University in Saudi Arabia have found effective new ways to control the dormancy of grapes and other fruiting plants, using high-tech plasma to wake them from their winter sleep.
This work can help expand the planting of native fruit trees and ornamental plants into temperate regions into parts of the world where winter is lighter, including the southern United States, Mexico, Brazil, South Asia, Southeast Asia, and the Middle East. This can also reduce the problems caused by rising temperatures due to global warming in certain parts of the world.
The work was carried out by a team of scientists consisting of Habib Khemira, a horticulture expert; Zaka-ul-Islam Mujahid, a plasma physicist; and Taieb Tounekti, plant physiologist. "The artificial method for releasing dormancy is expected to become more important in the near future due to global warming," said Mujahid, who will present work next week at the 71st American Physical Society Annual Electronic Gas Conference and the 60th Annual meeting of the APS Division of Plasma Physics, which took place on November 5-9 at the Oregon Convention Center in Portland.
Although this method works in the laboratory, it still needs to be tested in the field and proven to be commercially and economically feasible to benefit industrial scale food production.
To Sleep, Talk to Bud
When winter crawls toward a quiet garden, plants feel a longer night and faster days and adapt to being inactive. Starting in autumn, they spill their leaves, slow down their metabolic activity and enter a "sleepy" state where they will survive the cold months.
The plant was released from his sleep by Jack Frost because of the cold winter itself. They feel cold, tracking cold days in the middle of winter, and when enough cold days occur, plants respond by increasing their metabolic processes which lead to shoot rest and shoot growth when warm spring days arrive.
But when plants grow in cool winter areas or the climate becomes warmer, they may not receive enough cold to release their shoots on time. Sometimes with a sloping weather pattern, you will find flowers, fruit and dormant buds all on the same tree at the same time. Throughout fruit orchards, this can lead to synchronous plant ripening – undesirable results for farmers because it complicates operations such as pest control and increases labor costs and decreases crop yields.
One challenge for modern agriculture is finding ways to encourage the maximum number of shoots in plants to grow, and to produce flowers and fruit at the same time. This will be the same as the larger leaf area to feed the growing fruit, and for larger plants that will be ready to be taken at the same time.
Novel Solutions that Begin with Casual Discussions
The Saudi Arabian team achieved new ways to trick plants from dormancy by subjecting them to plasma, specifically, heat, ionized gas is sometimes referred to as the fourth state of matter – in addition to solids, liquids and ordinary gases. You can find plasma in lightning strikes, star cores, heavenly aurora, and old school neon lights.
Scientists use plasma for everything from igniting fusion test reactors to sterilizing medical implants. The special team uses it to treat wine vines that are not active.
They found that plasma exposure causes oxidative stress in plants, the exact same signal caused by cold cells in dormant plant cells whose buds respond by arousing. By treating grape buds with plasma, the researchers found they could release plant dormancy – and far faster than weather and be safer than existing artificial methods, which rely on spraying plants with chemicals.
Mujahid said the work began with a relaxed discussion he had with his colleague Khemira, a senior researcher at the Jazan University Center for Research and Environmental Studies. Khemira was describing his work on oxidative stress on wine buds, and they found that no one had ever tried using plasma to cause oxidative stress and release it from dormancy. They immediately tested the approach, and succeeded. Taieb analyzed the sample and found that plasma treatment caused oxidative stress similar to what was achieved by natural cyanide and hydrogen cyanamide.
"Some of the results of our first successful trials were phenomenal, and we do not believe that to be true," Mujahid said. Even just a few minutes of plasma treatment of shoots that have never seen cold weather allow plants to achieve the same, if not better, shoot breaks as control plants that experience optimal cold conditions (60 days from exposure to temperatures around 5 degrees Celsius).
They tested the approach to various grape varieties sourced from different regions and found that it could reliably work on everything. Generally farmers improve the problem of lack of cold by spraying trees with chemicals such as hydrogen cyanamide. The problem is that hydrogen cyanamide or other chemicals is only effective if the plant secures a significant proportion of its cold needs from natural cold. In addition, hydrogen cyanamide is also toxic to humans, wildlife and plants themselves. Because of this, chemicals have been banned in several countries, Khemira said.
Whether a newer, greener approach to using plasma to treat dormant shoots taking off will depend on a number of things, including whether it will work effectively in the field as well as in the laboratory. This needs to be tested on plants other than grapes, and equipment costs also need to be accounted for.
"There is still a lot of work to test its effectiveness and feasibility," Mujahid said. "We are in the process of finding the right parameters to bring it to the field but can be used in just a few years."
Khemira said that if practical aspects were successful and a new approach was proven commercially to revolutionize the way we plant a lot of plants. Researchers have submitted patent applications for shipping methods and systems.