J.M. Carter, E. Brown, N.B. Bowden
University of Iowa,
Keywords: agriculture, harvest, gasotransmitter, fertilizer
Summary:Hydrogen sulfide is well known as a poisonous gas, but it is also a key gasotransmitter in humans and in plants, and it has a large effect at low concentrations. Gasotransmitters are synthesized by the action of enzymes in cells and used to affect numerous cell cycles and to communicate between cells. Recent work has shown that hydrogen sulfide is an important gasotransmitter in plants that can accelerate their growth and increase their survival to environmental stressors such as high salinity, drought, high temperatures, and low iron content in soils. Most of the work that has been reported with hydrogen sulfide is based on the first few weeks of growth, and much of this work was completed with aqueous hydrogen sulfide that released high concentrations of hydrogen sulfide into the atmosphere due to its low boiling point (-60°C). To address this problem, recent work has focused on the use of chemicals such as GYY-4137 that slowly release hydrogen sulfide over days to weeks to months. These chemicals provide a method to study how milligram dosings of hydrogen sulfide affects the growth of plants. We recently developed the synthesis of chemicals that slowly release hydrogen sulfide and other chemicals that are naturally found in the environment. These dialkyldithiophosphates were synthesized in one step from inexpensive, commercially available starting materials, and their stabilities and rates of release of hydrogen sulfide were measured using a hydrogen sulfide electrode and NMR spectroscopy. We thoroughly characterized over a dozen examples of these chemicals to investigate how they can be applied to solve problems in agriculture. Our work demonstrated that these chemicals slowly release hydrogen sulfide in the presence of water, and they also release phosphoric acid and fatty alcohols that are naturally present in the environment. We designed these hydrogen sulfide delivery agents to be safe for the environment and release natural, nonpolluting chemicals. Prior work by other focused on the early growth of plants exposed to hydrogen sulfide, but we focused on the long-term growth and harvest yields of plants exposed to hydrogen sulfide. In many studies only milligram quantities of dialkyldithiophosphates or GYY-4137 delivered when the seeds were planted were necessary to greatly increase their growth and harvest yields. We discovered that only 10 milligrams of GYY-4137 added adjacent to radish seeds at planting was needed to more than double the weight of harvested radishes. Ten milligrams of GYY-4137 would release a maximum of 1.8 mg of hydrogen sulfide over the 4.5 weeks of growth of the radish plants. We also investigated the growth of lettuce plants and nearly doubled their weight after the addition of GYY-4137 to their stems and leaves. Finally, we will report how dibutyldithiophosphate increased the growth of corn plants and improved the harvest yields of pea plants by 44%. These results demonstrate that only miniscule amounts of chemicals that release enough hydrogen sulfide to have a positive effect on the harvest yields of a variety of plants.