Blue Carbon in Coastal Freshwater Marshes on the Barrier Islands of Virginia: Belowground Carbon Pools
Some coastal ecosystems sequester substantially more carbon than landlocked systems; the carbon associated with oceanic influences is called blue carbon. These ecosystems are disproportionally important in the global carbon budget based on their size. Most blue carbon research has focused on mangroves, seagrass beds, and salt marshes. Few studies have examined the blue carbon potential of coastal freshwater marshes. Barrier islands frequently flood, with seawater reaching interior ecosystems. We examined freshwater marshes on Virginia’s barrier islands for their possible role as blue carbon systems. We studied four interior marshes on Hog Island, which varied in proximity to the ocean and a trail berm. Sediment deposition was measured using sediment plates, root decomposition was measured with litterbags, and BGNPP was quantified using in-growth cores. There were no significant site differences in inorganic sediment deposition. BGNPP was significantly greater for sites closer to the beach (256 g m-2 yr-1) than farther sites (191 g m-2 yr-1). BGNPP was significantly greater for sites below the berm (271 g m-2 yr-1) than for sites above the berm (176 g m-2 yr-1). Decay rates for sites close to the beach (k=0.00275 day-1) were greater than for sites farther from the beach (k=0.00145 day-1). Unexpectedly, decay rates at sites open to the ocean (k=0.00179 day-1) were less than rates behind the berm (k=0.00235 day-1). These sites were generally less productive belowground than salt marshes and root decay rates were generally higher than in mid-Atlantic salt marshes.
178 • Elizabeth D. Evans, Safaa H. Al-Hamdani, Benjamin Blair
Physiological Responses of Roselle (Hibiscus sabdariffa) to Drought Stress and Determination of Antioxidant and Nutrient Content
Roselle (Hibiscus sabdariffa) belongs to the Malvaceae family. It is an erect, mostly branched, annual, herbaceous subshrub that grows mainly in warm and humid tropical and subtropical climates. Roselle calyces have been used in folk medicines for many years and have been proven to lower blood pressure in patients with hypertension and type II diabetes. This research project was carried out to examine the effect of drought on inducing elevation in antioxidant content in the calyxes. Additionally, selected physiological responses of roselle to drought were examined. The plant appeared to osmotically adjust to drought and the total phenolic compounds were elevated in the stressed plants. The photosynthetic rate, stomatal conductance and photosynthetic pigments were significantly reduced in the stressed plants. Additional experiments were carried out in the field to evaluate the nutrition value of the stem, leaf and calyxes of two roselle varieties (thai red and red drops). The two varieties appeared with relatively high accumulation of micronutrients and macronutrients and with the calyx protein content of 5.19% and 20.1 and 62.7 ADF and TDF respectively. The collective data from this research can be utilized to promote the hypothesis that roselle can be utilized as an excellent source for supplemental food for human consumption and should be promoted commercially.
179 • Austen C. Stoelting1, Safaa H. Al-Hamdani1, Mustafa Morsy2
Selected Physiological Responses of Tomato Plant to Drought and High Temperature as Influenced by Symbiotic Interaction With Curvularia Virus and Curvularia protuberata Fungus
This study was carried out to evaluate the symbiotic interaction between Curvularia Thermal Tolerance Virus (CThTV), Curvularia protuberata,and tomato plant (Solanum lycopersicon) in combating drought and high temperature. The plant was germinated under greenhouse conditions and the seedlings were divided between three treatments, plants free of the virus and fungus (control); plants inoculated with the virus and fungus; and plants inoculated with just the fungus. Twelve selected samples from each treatment were individually planted in one gallon pots containing organic potting soil. The plants were allowed to grow for two weeks to ensure healthy establishment. The drought treatment was applied to all three treatments by holding the watering process. After two weeks, the plants started showing visible symptoms of drought, including wilting and slight chlorosis. Physiological measurements of six plants from each treatment were taken to determine the impact of drought. Photosynthetic measurements, photosynthetic pigments, plant dry weight, osmotic potential, and total soluble sugar content were not significantly different among all the treatments. The plants’ response to drought appeared to have similar results during pre- and post-anthesis, indicating that the symbiotic interaction between the virus, fungus, and plant had no impact on drought tolerance of the tomato plant. The second experiment was carried out using plants inoculated in the same way as above to determine the impact of the three-way interaction on heat tolerance. Four randomly selected plants were assigned from each treatment to the heating units and allowed to grow for seven days. The temperature of the heating units was adjusted to 45˚C during the 14 hours of daylight to 25˚C during the night. The plants growing under symbiotic association with the virus and fungus showed the least wilting symptoms followed by the virus-free plants, and the control. Photosynthetic rate was significantly higher in the symbiotic plants with both the virus and fungus, followed by virus-free plants, and the control. However, stomata conductance and photosynthetic pigments did not show significant differences between the treatments
1 Jacksonville State Univ. Biology Dept.; 2 Univ. of West Alabama Biology Dept.
