Phytohormones Trigger Drought Tolerance in Crop Plants: Outlook and Future Perspectives.

In the past and present, human activities have been involved in triggering global warming, causing drought stresses that affect animals and plants. Plants are more defenseless against drought stress; and therefore, plant development and productive output are decreased. To decrease the effect of drought stress on plants, it is crucial to establish a plant feedback mechanism of resistance to drought. The drought reflex mechanisms include the physical stature physiology and biochemical, cellular, and molecular-based processes. Briefly, improving the root system, leaf structure, osmotic-balance, comparative water contents and stomatal adjustment are considered as most prominent features against drought resistance in crop plants. In addition, the signal transduction pathway and reactive clearance of oxygen are crucial mechanisms for coping with drought stress via calcium and phytohormones such as abscisic acid, salicylic acid, jasmonic acid, auxin, gibberellin, ethylene, brassinosteroids and peptide molecules. Furthermore, microorganisms, such as fungal and bacterial organisms, play a vital role in increasing resistance against drought stress in plants. The number of characteristic loci, transgenic methods and the application of exogenous substances [nitric oxide, (C28H48O6) 24-epibrassinolide, proline, and glycine betaine] are also equally important for enhancing the drought resistance of plants. In a nutshell, the current review will mainly focus on the role of phytohormones and related mechanisms involved in drought tolerance in various crop plants.

Omeprazole alleviates water stress in peppermint and modulates the expression of menthol biosynthesis genes.

Water stress is a worldwide agricultural challenge that limits crop growth and quality. Chemical compounds that promote tolerance to water stress, such as omeprazole showed recently promising results. The present study investigates the effect of weekly drenching applications of 0, 10, 50, 100, or 200 µM omeprazole on Mentha piperita (peppermint) subjected to water stress by watering at 100%, 70%, and 50% of container substrate capacity for 7 weeks in an experiment that spanned two seasons. Peppermint that received higher doses of omeprazole showed increased plant height, leaf number, leaf area, and dry weight under normal and water stress conditions. The amounts of chlorophyll and proline in the leaves as well as gas exchange increased in omeprazole-treated plants relative to the control plants. Omeprazole treatment also resulted in increased activity of the enzymes catalase and ascorbate peroxidase, reduced accumulation of the reactive oxygen species hydrogen peroxide, increase in the essential oil ratio, and improvement in essential oil composition. Omeprazole-treated plants showed higher ratios of menthol and menthone composition relative to the control plants. The changes in essential oil composition were associated with increased expression of genes associated with the menthol biosynthesis pathway. These findings indicate that omeprazole can ameliorate water stress in peppermint by increasing vegetative and root growth; increasing chlorophyll amount, photosynthetic rate, and gas exchange; reducing water loss by boosting leaf water potential and relative water content; increasing proline content; and modulating the gene expression of secondary metabolites.

Heuchera Creme Brulee and Mahogany Medicinal Value under Water Stress and Oligosaccharide (COS) Treatment.

Food borne pathogens cause serious human illnesses and diseases and their control using natural bioactive compounds becomes essential for the progress of agricultural and food industries. Developing novel tools to enhance the medicinal values of traditional horticultural medicinal crops is one of the promising methods for achieving food borne pathogens control. In this study, oligosaccharide water solutions were applied to Heuchera Creme Brulee and Mahogany subjected to a normal irrigation interval (2 days) or to prolonged irrigation intervals (6 days) for 6 weeks. Plant morphological, physiological, and metabolic markers associated with the bioactivity of leaf extracts against selected microbes. Oligosaccharide-treated plants showed significant increases in all morphological parameters during normal and prolonged irrigation intervals as compared to those of the controls. Morphological improvement associated with a significant increase in chlorophyll, carbohydrates, proline, K, Ca, phenols, and free and total ascorbate and antioxidants. Superoxide dismutase, catalase, and ascorbate peroxidase activities were higher, while H2O2 accumulated to a lower extent in oligosaccharide-treated plants. These morphological and metabolic changes associated with increased antibacterial and antifungal activities of leaf extracts and their activities were comparable to antibiotics and antifungal agents (minimum inhibitory concentrations values were 0.5 -0.20 mg-1mL for bacteria and 0.08 -0.20 mg-1mL for fungi in Mahogany). The application of oligosaccharide and/or water stress might be of great value for producing natural bioactive compounds for food borne pathogens control.

Phenolic Compounds of Catalpa speciosa, Taxus cuspidate, and Magnolia acuminata have Antioxidant and Anticancer Activity.

Tree bark represents an important source of medicinal compounds that may be useful for cancer therapy. In the current study, high-performance liquid chromatography with diode-array detection (HPLC-DAD) was used to determine the profile of the phenolic compounds of Catalpa speciosa, Taxus cuspidata, and Magnolia acuminata bark extracts. The antioxidant and anticancer bioactivities against different cancer cell lines were investigated. M. acuminata exerted significantly higher antioxidant activities in the diphenyl picrylhydrazine and ß-carotene-linoleic acid assays than the other species. In C. speciosa, novel profiles of phenolic acids (ferulic acid was the predominant compound) and catechin were detected. In T. cuspidata, six phenolic acids were detected; the predominant compounds were hydroxycaffeic acid and protocatechuic acid. In M. acuminata, two phenolic acids and three catechins were detected; catechin was the predominant compound. The three species exerted clear anticancer activity against MCF-7, HeLa, Jurkat, T24, and HT-29 cells, with the strongest activity found in the extracts from M. acuminata. No antiproliferative activity against normal cells was found. Flow cytometry revealed greater accumulation of necrotic and early/late apoptotic cells in various treated cancer cells than in untreated control cells, and protocatechuic acid induced a similar accumulation of necrotic cells to that of the bark extracts. Caspase-3 and -7 activity was increased in cancer cells treated with different bark extracts; the highest activity was found in the M. acuminata treatment. Our results suggested that the treatment of cancer cells with bark extracts of M. acuminata, C. speciosa, and T. cuspidata, and protocatechuic acid induced apoptosis, suggesting an association between anticancer activities and individual phenolic compounds.