The physiological responses to salt stress were measured in Chenopodium quinoa. In a greenhouse experiment, salt water was applied to the quinoa varieties, Chipaya and KU-2, and to the model halophyte Thellungiella halophila to assess their relative responses to salt stress. Height and weight data from a seven-week time course demonstrated that both cultivars exhibited greater tolerance to salt than T. halophila. In a growth chamber experiment, three quinoa cultivars, Chipaya, Ollague, and CICA 17 were hydroponically grown and physiological responses were measured with four salt treatments. Tissues collected from the growth chamber treatments were used to obtain leaf succulence data, tissue ion concentrations, compatible solute concentrations, and RNA for real-time PCR. Stomatal conductance and fresh weight were measured to determine the degree of stress and recovery. The expression profiles of SOS1, NHX1, and TIP2, genes involved in salt stress, showed constitutive expression in root tissue and up-regulation in leaf tissue in response to salt stress. These data suggest that quinoa tolerates salt through a combination of exclusion and accumulation mechanisms.

Corn is one of American agriculture's greatest success stories, where we have witnessed incredible increases in yield potential over the last half-century. However, abiotic stress is still the primary limiting factor preventing plants from reaching their true yield potential. In addition, agriculture is not exempt from the deleterious effects of changing weather patterns and the altered climate our world will face as time progresses. Thus, increasing our understanding of how crops interact with their environment both above and below the soil will be crucial to increasing production on a global scale while maximizing profitability at a local level. Five studies were carried out to quantify the relationship between corn and multiple abiotic factors, including temperature, moisture, and nitrogen. In study one, Corn seed germination as a function of temperature was quantified, and the effects were compared between soybean and cotton, both major agronomic crops in Mississippi. Study two determined the effects of osmotic stress on corn seed germination, and commercial corn hybrids' variability was explored. In study three, functional relationships between temperature and early season growth and development were quantified, and the concept of a simple mathematical model for predicting growth as a function of temperature was explored. Study four exemplified the effects of increasing waterlogging durations from 0 to 14 days and determined critical limits for above and below-ground growth. Finally, in study five, growth, development, and physiology were determined as a function of nitrogen concentration. In addition, optimum concentrations to maximize vigor were estimated. Data generated from these studies exemplify how abiotic stress significantly affects corn during germination and early season growth and development. These datasets will be valuable foundations to build on as we explore how abiotic stress affects all growth stages of corn and other important agronomic crops. Functional relationships generated from these studies will be useful to update crop simulation models. Both simple and complex mathematical models have promising implications in emerging and developing precision and predictive agricultural technologies.

For migratory birds the highly dynamic atmosphere plays a significant role during every part of their migratory flight. It is essential for the success of their reproduction that they arrive at the breeding areas in the right time span and in good condition. It follows then a successful and timely migration to their breeding areas is of critical importance to these bird populations. Seemingly, different weather conditions can either be beneficial or detrimental and specifically wind is thought to be the greatest factor for a successful migration. Migratory birds have to, due to various cues, decide when to stop for stopovers as well as decide for next take off from that stopover site. In this study I’ve examined if four different abiotic factors, (wind direction, wind speed, temperature and precipitation) affect snow bunting’s propensity to do stopovers at a coastal site in north of Sweden during spring migration. I’ve also examined if there is a variation in arrival at said site between the years during spring migration. To make this study possible I’ve captured snow buntings at Umedeltat field station during spring 2018 and combined my data with data from 2017 as well as data from 2012. I found no significant correlation with either wind speed, temperature nor precipitation and captured birds. I suggest that a longer study that takes into account more abiotic factors and examines the roles of spatial and temporal patterns during migration of snow buntings needs to be conducted. As the climatic conditions are changing in western Europe it is of importance to monitor how birds are influenced by weather, especially an Arctic-breeding bird, as the climate change is presumed to be greater in those regions.

The relative importance of abiotic versus biotic top-down factors on structuring tundra plant communities is debated. With climate change already strongly affecting the tundra ecosystem, understanding which factors will prevail is vital. Tundra plant communities are presumed to be predominantly structured by their abiotic conditions yet grazing by reindeer (Rangifer tarandus) has a major effect on composition and diversity. It is increasingly recognized, however, that these factors cannot be considered in isolation. Here, I aim to test the relative and interactive effect of abiotic and top- down factors on vegetation structure in the Swedish mountain tundra. Using direct measurements of reindeer grazing via tri-axial accelerometers (from two summers, 2019 and 2020) coupled with remotely-gathered data on landscape features, I examine how species richness and coverage of vascular plants, bryophytes and lichens (sampled in 2022) are driven by grazing duration and abiotic conditions. Abiotic factors, specifically aspect and soil wetness, prevailed as the dominant drivers of local vegetation patterns. Clear interactions between factors were also observed. Reindeer grazing duration had predictable but weak effects on richness, with responses predominantly observed on south-facing slopes. Additionally, soil wetness interacted with grazing duration, with wetter areas grazed far less. These results demonstrate the importance of considering interactions between abiotic and biotic factors, providing a better understanding of how tundra plant communities in northern Sweden might change under future climate change or different grazing regimes. The observed interactions imply divergence in vulnerability between slopes and the potential for effects of herbivory to be altered under future hydrological conditions. I emphasize that future studies should continue to disentangle these relationships.

Abiotic stresses like salinity, drought, and extreme temperature are constantly on the rise, posing a very high risk to global agricultural productivity and food security. Hence, understanding stress signaling pathways can help engineer plants that can better withstand stress in unfavorable conditions. The salicylic acid (SA) signaling pathway has been widely studied for its important role in mediating abiotic stress in plants. In tobacco plants, Salicylic Acid Binding Protein 2 (SABP2), a methyl esterase enzyme, catalyzes the conversion of methyl salicylate (MeSA) to SA, which triggers the defense response via the SA-mediated signaling pathway. SIP-428 (SABP2 Interacting Protein-428) is an NAD+ dependent SIR2-like (Silent Information Regulator) deacetylase enzyme that likely interacts with SABP2 during SA biosynthesis. In previous studies, SIP-428 has been shown to be a negative regulator of plant growth under abiotic stress (NaCl and mannitol in vivo). Reactive Oxygen Species (ROS) are oxidizing oxygen products that accumulate under stress conditions, and at high levels can be very harmful to plants. Antioxidant enzymes such as catalase (CAT), guaiacol peroxidase (POD), ascorbate peroxidase (APX), and superoxide dismutase (SOD) are actively involved in lowering the ROS levels in the cell by combating the oxidative stress. The objective of this study was to analyze the regulatory functions of SIP-428 in ROS signaling of tobacco plants through the biochemical quantification of POD and CAT activities. We investigated the SIP-428 RNAi-silenced tobacco plants for the POD and CAT enzyme activities in Osmotic (Mannitol) and Salinity (NaCl) stressed plants. Our results showed that SIP-428 plays a significant role in modulating antioxidant enzymes in stressed plants. This study has improved our understanding of some regulatory roles of SIP428, and its application can be used to enhance stress tolerance via the use of synthetic biology.

Lipid transfer proteins (LTPs) belong to the pathogenesis-related protein family (PR-14) and are thought to participate in plant defense mechanisms. In this study, we characterize the function of an Arabidopsis thaliana mutant ltp12 (AT3G51590), a homologous lipid transfer protein to SIP470 from Nicotiana tabacum for its role in abiotic and biotic stress. SIP470, a lipid transfer protein, was found to interact with SABP2 in a yeast-two hybrid screen. SABP2 in tobacco is required for inducing a robust SAR response. The objective of this research is to understand the role of LTP12 in mediating abiotic stress as salicylic acid plays an important role in both abiotic and biotic stress in plants. For this research, stressor chemicals, NaCl (salinity), mannitol (osmotic stress), and drought (no water or PEG) will be used. Seedlings were initially germinated and grown on artificial plant growth MS media. The similar-sized young seedlings were transferred to MS media plates supplemented with or without stressor chemicals. Oxidative stress analysis of various antioxidant enzymes, such as catalase (CAT), superoxide dismutase (SOD), and peroxidase (POD) will be performed. The Na+ homeostasis for salinity stress will be studied using CoroNaTM dye and confocal microscopy. Our lab has T-DNA insertion knockout mutants of LTP12 that we will be used in the proposed studies. Here, we hypothesize that mutant ltp12 plants will be hypersensitive to abiotic stressors like NaCl, mannitol, and drought, while wildtype Col-0 will be markedly more tolerant. Reports also suggest that knockout lines of other lipid transfer proteins show a defective growth phenotype and lower expression of systemic acquired resistance (SAR). Moreover, to gain a better understanding of both lines' responses to abiotic stress, we need to carry out further studies on the soil as well. The study will also discuss the subcellular localization of ltp12 in Arabidopsis, which will provide an idea of its functional mechanism. Understanding the role of lipid transfer proteins can lead to the development of transgenic plants that are more tolerant to abiotic stresses and climate change.

Habitat loss is among the biggest threats to conservation worldwide, so habitat restoration plays an increasing role in endangered species management. This is especially true for species with high site fidelity, such as nesting marine turtles. Sand replenishment is commonly used to restore coastal beaches after severe erosion events, and may affect marine turtles and other species that live or reproduce in that habitat. I investigated how abiotic characteristics of sand used in a dune restoration project at Archie Carr National Wildlife Refuge, Florida, affected reproduction of the federally-endangered green turtle (Chelonia mydas). Sand structure and composition can affect egg development and hatching success by altering nest conditions, with nests in fine-grain or very coarse sand suffering decreased hatching success. I determined that calcium carbonate content (27.0% ± 1.4 SE vs. 15.1% ± 3.8 SE), moisture content (3.29% ± 0.26 SE vs. 4.59% ± 0.25 SE), and grain size (427.53 µm ± 14.1 SE vs. 274.66 µm ± 29.1 SE) differed significantly between natural and restored dunes. Hatching success of green turtles (44.7% ± 6.2 SE vs. 65.8% ± 5.3 SE) was significantly lower on restored dunes compared to natural dunes with an estimated loss of 22,646 hatched eggs. Hatching success also decreased as the nesting season progressed. These results demonstrate the importance of regulating fill material used in beach restoration projects; substrate characteristics are easily evaluated and can significantly influence marine turtle hatching success.

The Leaf Economics Spectrum (LES) describes the continuous range of leaf ecophysiological strategies that plants across the globe utilize to achieve a net-positive return on their resource investment. This spectrum is measured by traits such as leaf mass per area, leaf nitrogen, and leaf lifespan. Unsuitable leaf trait combinations are selected against in nature due to a net-loss on the return of initial resource investment, while some potentially extremely effective trait combinations may not be possible due to genetic constraints. Existing genetic variation in LES traits, however, suggests the spectrum may be less rigid than previously expected. To test this, we exploit phenotypic plasticity by subjecting cultivated sunflower, Helianthus annuus, to environmental stress to generate variability in LES traits. In a greenhouse experiment, treatment groups of Helianthus were exposed to six varying intensities each of four acute stress applications: nutrient limitation, high soil salinity, heat, and simulated herbivory. Leaves formed during the onset of stress and post-stress were sampled to measure leaf traits; changes in plant fitness were estimated through total plant biomass and the time of first flowering. Results from statistical analyses show a variety of significant effects that stress applications had on plant growth and LES traits. Our findings explore the possibility of achieving off-axis LES trait combinations through salt-induced trait plasticity, and if further studies are needed to reassess the rigidity of the spectrum.

Abiotic stresses cause extensive loss to agriculture production worldwide. Cowpea is an important legume crop grown widely in tropical and subtropical regions where high temperature, ultraviolet-B (UVB) radiation and drought are the common stress factors limiting production. Various vegetative, physiological, biochemical and reproductive plant attributes were assessed under a range of UVB radiation levels in Experiment I and in a combination with two doses of each carbon dioxide concentration [CO2], temperature, and UVB radiation and their interactions in Experiment II by using six cowpea genotypes and sunlit plant growth chambers. The dynamics of photosynthesis and fluorescence processes were assessed in 15 cowpea genotypes under drought condition in Experiment III in pot-grown plants under sunlit conditions. A distinct response pattern was not observed in cowpea in response to UVB radiation form 0 to 15 kJ; however, plants grown under elevated UVB showed reduced photosynthesis resulting in shorter plants and produced smaller flowers and lower seed yield. Increased phenolic compounds appeared to be a defense response to UVB radiation. The growth enhancements observed by doubling of [CO2] were not observed when plants were grown in combination with elevated UVB or temperature which also showed the most detrimental effects on plant growth and seed yield. Results form Experiment I and II revealed that cowpea reproductive traits were highly sensitive to abiotic stresses compared to the vegetative growth and development. A total stress response index (TSRI) technique, derived from all vegetative and reproductive parameters, was used to screen genotypes for their stress tolerance to UVB or combination of stresses. An increase in water use efficiency while maintaining higher rate of photosynthesis was an important drought tolerance mechanism in tolerant cowpea genotypes. Using principal component analysis technique, four groups of the genotypes were identified for their drought tolerance. Evaluating same genotypes across stress conditions revealed that no single genotype has the absolute tolerance characters to all stress conditions. The identified diversity for abiotic stress tolerance among cowpea genotypes and associated traits can be used to develop tolerant genotypes suitable for an agro-ecological niche though traditional breeding or genetic engineering methods.

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