Effect of Selenium on Glucosinolate and Isothiocyanate Concentrations in \u3cem\u3eArabidopsis thaliana\u3c/em\u3e and Rapid-Cycling \u3cem\u3eBrassica oleracea\u3c/em\u3e

Brassica vegetables play a unique nutritional and sensory role in human diets around the world. Their characteristic flavors come from the break down products of glucosinolate (GS) compounds, a large group of nitrogen (N) and sulfur (S) containing glucosides. Glucosinolates are hydrolyzed by myrosinase to isothiocyanates (ITCs) which are biologically active. Mounting evidence of this process is of scientific interest due to the potential for high consumption of Brassica vegetables containing several GSs and their respective hydrolysis products that are associated with cancer chemoprevention. Glucosinolates are sulfur-rich hydrophilic, nonvolatile plant secondary metabolites; and. over the past few decades, their importance has increased following discoveries of their hydrolysis products, ITCs, as potential anticarcinogens. The importance of selenium (Se) to human health has increased in recent years due its antioxidant potential and cancer suppression properties. Recent studies have demonstrated that certain Se containing compounds like Se-methyl-Se-Cysteine and Se-methionine are effective chemoprotective agents, reducing the incidence of breast, liver, prostate, and colorectal cancers in model systems. Brassicaa species are able to hyperaccumulate selenium at concentrations of up to 10-15 mg Se·g-1 dry weight in their shoots while growing on naturally-occurring soils containing only 0.2-10 mg Se·kg-1. The non-specific integration of Se into the S assimilation pathway enables the plant to metabolize selenoamino acids, selenocysteine and selenomethionine, into proteins. The process is believed to be the major contributor of Se toxicity in plants. The ability of hyperaccumulators to accrue and tolerate high concentrations of Se is thought to be associated with a distinct metabolic capacity that enables the plants to convert these selenoamino acids into non-protein amino acids

The Effect of Abscisic Acid on Tomato Calcium Partitioning and Fruit Quality

Tomato (Solanum lycopersicum) is a widely employed plant model system for studying fruit metabolism, development and ripening. Various environmental stress factors, such as drought and high relative humidity, can cause calcium (Ca) deficiency and lead to physiological diseases such as blossom-end rot (BER) in tomato fruit. Recent studies demonstrate that abscisic acid (ABA) triggers whole-plant and fruit-specific mechanisms to increase fruit Ca uptake and prevent BER development. The objective of this study was to evaluate the effects of exogenous ABA applications during plant development on tomato carotenoid pigments, soluble sugars, organic acids, aromatic volatiles, carbohydrates, and mineral nutrient content in ripe fruit, and to assess the impacts of ABA applications on BER by evaluating how exogenous ABA will affect the distribution of Ca between the leaves and fruit. There were a series of three experiments that examined two types of tomato plants, micro tomato and a commercial tomato cultivar \u27Mt. Fresh Plus\u27. ABA was exogenously applied to the foliar and/or root tissue. Leaves were harvested and analyzed for chlorophylls, carotenoids, and Ca concentrations. Fruit tissue was harvested at red ripe maturity and analyzed for yield, BER and fruit quality parameter, such as carotenoids, soluble sugars, organic acids and aroma volatiles. The results indicate that applications of ABA treatments to tomato plants decreased the partitioning of Ca into the leaves while increasing concentrations in the fruit tissue. ABA treatments, in combination with the Ca treatment of 180 mg⋅L-1 (milligram per liter), decreased the incidence of BER. Further, ABA treatments decreased BER even in the presents of low Ca in the fertilizer solution. Results indicate that ABA treatments are most effective in the early stages of plant development. This study demonstrated that ABA is a viable treatment to significantly improve tomato fruit quality. Specifically, ABA treatments increased tomato fruit carotenoids and soluble sugar, while decreasing organic acid concentrations. However, ABA treatments had a detrimental effect on aroma volatile concentrations. ABA treatment applications in conjunction with low Ca treatments did not prove to be effective in improving tomato fruit quality. This study demonstrated that foliar spray ABA applications are more effective than root ABA applications

Seed priming attenuates the impact of salt stress and enhances lettuce yields

Salt stress is a major factor that contributes to reduced lettuce productivity. Seed priming has emerged as a promising technique to improve crop stress tolerance. In this study, Romaine lettuce seeds were primed with calcium chloride (CaCl2), distilled water (hydro), and potassium nitrate (KNO3) to test their effectiveness in improving salt stress tolerance. Lettuce seeds treated with hydro, 50 mM CaCl2, and 0.5% KNO3 were exposed to 0 or 100 mM sodium chloride (NaCl). Priming treatments significantly increased lettuce's fresh mass by 22%–61% under salt stress. Hydro-primed lettuce showed the most significant increase in root mass (109%), a 38% higher root length, a 35% increase in surface area, and a 25%–40% increase in volume, tips, forks, and crossings of roots. The hydro-primed lettuce had higher gas exchange rates than the non-primed control, followed by the KNO3- and the CaCl2-primed lettuce. Furthermore, hydro-primed seedlings exhibited the highest proline accumulation (105%) under salt stress. The accumulation of sugars (up to 50%) in hydro- and CaCl2-primed lettuce led to a 56% decrease in electrolyte leakage and membrane damage. The correlation network analysis of the traits revealed that hydro-primed seedlings exhibited a higher + ve/-ve edge ratio, which indicates their greater resilience to salt stress than other priming techniques. Priming of seeds before planting offers the potential for improving resilience to stress