References

1. Height and Biomass of a Barley - Soybean Rotation Subjected to Gibberellic and Jasmonic Acid Treatments Matthew Johnson, Hunter Porter, Anna Graves, JonnaWhetsel, Matthew Naifeh, Dillon McDaniel, and Jim Bidlack Department of Biology, University of Central Oklahoma, 100 N. University Drive, Edmond, Oklahoma 73034 Abstract An experiment was conducted using gibberellic acid (GA), jasmonic acid (JA), and combinations thereof, to determine their potential in altering height and biomass of barley (Hordeumvulgare L.) grown during the winter, followed by soybean [Glycine max (L.) Merr.] grown during the summer. Treatments included 0.0 mM, 0.5 mM, 1.5 mM, and 3.0 mM applications of GA and JA, and combinations thereof, applied exogenously shortly after emergence for barley during the winter/spring and soybean during the summer/fall growing seasons. Plants were harvested at maturity and several measurements, including plant height, and weight of plant and plant components, were taken to assess responses to treatments. In general, GA increased height of soybean and JA decreased height of both barley and soybean. Although there were few significant differences among treatments in plant biomass, a trend demonstrated that JA consistently decreased biomass in both species. These results suggest that that GA and JA can be used to manipulate height in barley and soybean without substantial loss in biomass yield. Soil: The soil was prepared by creating a 1:1 composition of Miracle Gro brand potting soil and peat moss. To prevent soil loss, small stones were placed in the bottom of the pots near the opening. Table 4. Significance by analysis of soybean height (HEIGHT), total fresh weight (TOTFW), total dry weight (TOTDW), and pod dry weight (PODDW). *, ** Significant at the 0.05 and 0.01 probability levels, respectively. NS=Not Significant. Results and Discussion There was a significant difference in height of the barley plants, with either gibberellins or jasmonins having the effect of decreasing barley height (see Table 2). Treatments of 3.0 millimolargibberellic acid (GA) with 1.5 millimolarjasmonic (JA) acid produced the shortest plants on average, while the control for the experiment produced the tallest. Although the analysis of variance demonstrated that there were no significant changes in biomass of barley from treatments, the least significant difference test revealed that high concentrations of GA decreased dry biomass (see Table 3). There was also found to be no significant difference between those plants treated with JA, though there was a generalized trend of lower biomasses in plants that had been treated with both GA and JA. Unlike barley, soybeans demonstrated a significant increase in height when treated with higher amounts of gibberellins (see Table 5). Soybean height was not significantly affected by jasmonic acid treatment, however, there was a generalized trend that demonstrated some increase in height at the intermediate concentrations of jasmonins, as the tallest plant was at 3.0 GA and 1.5 JA. While there were no significant differences of soybean dry weight, there was a generalized trend of GA decreasing biomass. There was also a trend of JA decreasing the biomass of soybeans (see Table 6). Fig 3: Harvest of Soybeans Table 2. Average height (cm) of barley plants in response to gibberellic acid (GA) and jasmonic acid (JA) treatments. † Means followed by the same letter are not significantly different. Sowing: The experiment included plants grown in the large pots, with four replications for each of the sixteen treatments, which were arranged as a randomized complete block design on the roof of the Science Building. For barley, all pots were seeded with ~50 seeds on September 15 2011, with sixteen different types of treatment, including the control. For soybeans, pots were seeded with 20 seeds at even spacing on June 14 2012. Once the soybeans had germinated and allowed to grow, plants were thinned out until the three largest plants remained in a pot. Fig. 1: Measurement of Soybean Height Table 5. Average height (cm) of soybean plant in response to gibberellic acid (GA) and jasmonic acid (JA) treatments. † Means followed by the same letter are not significantly different. Fig 4: Measurement of Harvest Products Fig 2: Comparison of Soybean Heights Introduction Limited precipitation during the summer, coupled with high temperature, limits the production of food crops and energy crops in the Southern Great Plains. There is potential for use of some plant growth regulators (PGRs) such as jasmonic acid, or gibberellic acid, known to increase yield and growth of plant material (Bidlackand Buxton 1995), to provide drought tolerance under extreme conditions. However, limited information is available in the literature to demonstrate how exogenous applications of JA and other PGRs can be used to promote crop production under drought conditions (Hassaneinet. al. 2009, Hamayunet. al. 2001). This investigation evaluates the use of JA, in combination with gibberellic acid, in altering growth and biomass yield of barley and soybean grown as a grass-legume rotation in Oklahoma. Harvest: Height of soybeans was measured by using a meter stick to measure from the terminal bud to the base of the plant. These heights were averaged in order to calculate changes in average height more quickly. Soybeans were harvested by cutting them approximately 1 cm from the base of plant, and placed in pre-marked bags. The biomass of the stalk, the leaves, and the pods were measured. Once weighed, plants were then placed in pre-marked paper sacks and placed in a drying cabinet for two days. When dried, biomass of stalk, leaves, and pods were measured again. Height of the barley was measured by finding an approximate height for the middling plants and measuring from there, due to the large number of plants per pot. The barley was harvested by taking a pair of shears and cutting off the plant approximately 1.0 cm from the base of the plant. Plants were placed in pre-marked paper bags, and weighed as whole plants, and heads. Once weighed, the barley was placed in a drying apparatus for several days. When removed from the apparatus, the dry biomass of heads and stalks was measured. Conclusions The lack of mass increase in the heads of barley and pods of soybeans from any treatment of gibberellins or jasmonins leads to the conclusion that these are not effective at increasing yield of food crops. There may be some use of either gibberellins or jasmonins in the retardation of growth in grasses, as shown by the height decrease in barley, though whether this indicative of a similar results in other plants would need to be studied further. Treatments: Jasmonic acid (JA) and gibberellic (GA) acid were first dissolved in deionized water and then mixed with 1% Triton-x surfactant to help suspend PGRs and to promote absorption by leaf surfaces. Treatments included 0, 0.5, 1,5, and 3.0 mM JA or GA, which were applied by a hand sprayer (until saturation) on all parts of the plant. When undergoing treatment, all plants of the same treatment of gibberellins were isolated from other gibberellin treatments, and were placed near each other to ensure that none of the gibberellin treatment was wasted. Once the water from the gibberellin treatments had dried, the process was repeated with the jasmonins. Barley plants were treated in this fashion once in the fall, and once in the spring. Soybean plants were given one treatment, in the summer. Table 1. Significance by analysis of variance of barley height (HEIGHT) and total dry weight (DW). *, ** Significant at the 0.05 and 0.01 probability levels, respectively. NS=Not Significant. References Bidlack, J.E., and D.R. Buxton. 1995. Chemical Regulation of Growth, Yield, and Digestibility of Alfalfa and Smooth Bromegrass. J Plant Growth Reg 14:1-7 Hamayun, M., S. Khan, A Khan, J. Shin, B Ahmad, D. Shin and I. Lee. 2010. Exogenous Gibberellic Acid Reprograms Soybean to Higher Growth and Salt Stress Tolerance. J Agricult Food Chem 58:7226-7232 Hassanein, R., A. Hassanein, A. El-Din, M. Salama, H. Hashem. 2009. Role of Jasmonic Acid and Abscisic Acid Treatments in Alleviating the Adverse Effects of Drought Stress and Regulating Trypsin Inhibitor Production in Soybean Plant. Aust J Basic and ApplSci 3:904-919 Table 3. Average total dry weight (g) of barley plants in response to gibberellic acid (GA) and jasmonic acid (JA) treatments. † Means followed by the same letter are not significantly different. Table 6. Average total dry weight (g) of soybean plant in response to gibberellic acid (GA) and jasmonic acid (JA) treatments. † Means followed by the same letter are not significantly different. Materials and Methods Pots: Seeds were germinated in and plants were grown in 12-inch terracotta pots on the roof of the Science Building at the University of Central Oklahoma, Edmond, Oklahoma. The earthenware pots wick away moisture from the soil, which simulates drought conditions more effectively. Plants were watered once every two days, and any weeds found were removed. Due to the location of the experiment, there were not many herbivorous insects present to cause damage to the plants. Acknowledgements Funding for this project was provided by the University of Central Oklahoma CURE-STEM program and Office of Research & Grants. Many thanks to Johnston Seed Company, Enid, OK, for donation of barley seed, and to Ross Seed Company, El Reno, OK, for providing the soybean seed. We also thank volunteers from Dr. Bidlack’s Research Group for their participation on this project.