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Water stress is a primary abiotic stress that produces several morphological, physiological, biochemical and molecular alterations, which affect crop productivity. The aim of the present study was to evaluate and compare morphophysiological and biochemical characteristics and the hormone profiles of two sunflower inbred lines (C803 and R461-4) in response to moderate water stress at the early vegetative growth (V2) stage. Sunflower seedlings of C803 and R461-4 inbred lines obtained in pots filled with sand moistened to 60% field capacity were watered with (1) Hoagland's solution (control) or (2) mannitol 400 mM (moderate water stress) to field capacity on the fourth day after sowing. At V2, the seedlings were harvested and sectioned into the aerial part and roots. The parameters recorded for the analyses included the aerial part and root length, fresh and dry weight, leaf area and expansion rate, stomatal conductance, osmotic potential, phytohormones and total soluble carbohydrates. Among these parameters, the leaf area and stomatal conductance were the most affected by water stress. Abscisic acid and salicylic acid showed significant increases in the aerial part of water-stressed seedlings, while abscisic acid was the most abundant phytohormone in the roots. In addition, 28-Homocastasterone was the brassinosteroid with higher levels in both lines. This is the first report of teasterone in the sunflower. Finally, total soluble carbohydrates increased upon stressful conditions. Altogether, the water stress led to different parameter alterations dependent on the inbred line and its different sensitivity to water stress. [ABSTRACT FROM AUTHOR]

Brassinosteroids (BRs) are plant hormones that play an essential role in plant development and have the ability to protect plants against various environmental stresses, such as low and high temperature, drought, heat, salinity, heavy metal toxicity, and pesticides. Mitigation of stress effects are produced through independent mechanisms or by interaction with other important phytohormones. However, there are few studies in which this property has been reported for BRs analogs. Thus, in this work, the enhancement of drought stress tolerance of A. thaliana was assessed for a series of 2-deoxybrassinosteroid analogs. In addition, the growth-promoting activity in the Rice Lamina Inclination Test (RLIT) was also evaluated. The results show that analog 1 exhibits similar growth activity as brassinolide (BL; used as positive control) in the RLIT bioassay. Interestingly, both compounds increase their activities by a factor of 1.2–1.5 when they are incorporated to polymer micelles formed by Pluronic F-127. On the other hand, tolerance to water deficit stress of Arabidopsis thaliana seedlings was evaluated by determining survival rate and dry weight of seedlings after the recovery period. In both cases, the effect of analog 1 is higher than that exhibited by BL. Additionally, the expression of a subset of drought stress marker genes was evaluated in presence and absence of exogenous applied BRs. Results obtained by qRT-PCR analysis, indicate that transcriptional changes of AtDREBD2A and AtNCED3 genes were more significant in A. thaliana treated with analog 1 in homogeneous solution than in that treated with BL. These changes suggest the activation of alternative pathway in response to water stress deficit. Thus, exogenous application of BRs synthetic analogs could be a potential tool for improvement of crop production under stress conditions. [ABSTRACT FROM AUTHOR]

Brassinosteroids are a class of plant hormones that regulate a broad range of physiological processes such as plant growth, development and immunity, including the suppression of biotic and abiotic stresses. In this paper, we report the synthesis of new brassinosteroid analogues with a nitrogen-containing side chain and their biological activity on Arabidopis thaliana. Based on molecular docking experiments, two groups of brassinosteroid analogues were prepared with short and long side chains in order to study the impact of side chain length on plants. The derivatives with a short side chain were prepared with amide, amine and ammonium functional groups. The derivatives with a long side chain were synthesized using amide and ammonium functional groups. A total of 25 new brassinosteroid analogues were prepared. All 25 compounds were tested in an Arabidopsis root sensitivity bioassay and cytotoxicity screening. The synthesized substances showed no significant inhibitory activity compared to natural 24-epibrassinolide. In contrast, in low concentration, several compounds (8a, 8b, 8e, 16e, 22a and 22e) showed interesting growth-promoting activity. The cytotoxicity assay showed no toxicity of the prepared compounds on cancer and normal cell lines. [ABSTRACT FROM AUTHOR]

Plant hormones through signaling networks mutually regulate several signaling and metabolic systems essential for both plant development and plant responses to different environmental stresses. Extensive research has enabled the main effects of all known phytohormones classes to be identified. Therefore, it is now possible to investigate the interesting topic of plant hormonal crosstalk more fully. In this review, we focus on the role of brassinosteroids and ethylene during plant growth and development especially flowering, ripening of fruits, apical hook development, and root and shoot growth. As well as it summarizes their interaction during various abiotic stress conditions. [ABSTRACT FROM AUTHOR]