Seed Preconditioning with Natural and Synthetic Antioxidants Induces Drought Tolerance in Tomato Seedlings

Abstract

<jats:p>There is strong evidence that Ambiol® (a derivative of 5-hydroxybenzimazole) promotes drought tolerance in many plants; it is often suggested that this is the result of its antioxidant properties. Recent evidence has also shown that several natural antioxidants promote carrot germination under drought stress. Thus, it was hypothesized that seed preconditioning using natural antioxidants might confer drought tolerance. Ambiol®, ascorbic acid, β-carotene, lutein, and lycopene were chosen as antioxidants at concentrations of 0.1 mg·L<jats:sup>−1</jats:sup>, 1.0 mg·L<jats:sup>−1</jats:sup>, and 10 mg·L<jats:sup>−1</jats:sup>. A preconditioning treatment was applied by soaking tomato (<jats:italic>Solanum lycopersicum</jats:italic> L.) seeds in an antioxidant solution for 24 h. Of the antioxidants tested, 10 mg·L<jats:sup>−1</jats:sup> Ambiol®, 1.0 mg·L<jats:sup>−1</jats:sup> β-carotene, 1.0 mg·L<jats:sup>−1</jats:sup> ascorbic acid, and 0.1 mg·L<jats:sup>−1</jats:sup> lycopene were shown to increase shoot dry mass by 114%, 94%, 56%, and 83%, respectively, in droughted seedlings when compared with a droughted control. Similar benefits were observed in root dry mass, leaf area, photosynthesis, and water use efficiency. Proteins were extracted from the seeds of certain treatments, before and after germination, and separated using isoelectric focusing. Specific proteins were found to be induced through all preconditioning treatments, whereas Ambiol® and β-carotene were found to induce specific proteins, independent of those induced through imbibition, both before and after germination. This result suggests that Ambiol® and β-carotene evoke specific proteins that may confer drought tolerance to the key physiological processes studied. In addition, protein profiles of ascorbic acid, β-carotene, and Ambiol® after germination had fewer visible bands than the controls, suggesting an accelerated mobilization or conversion of proteins within the seed.</jats:p>

Ambiol Preconditioning Can Induce Drought Tolerance in Abscisic Acid-deficient Tomato Seedlings

“…In all tomato seedlings, there was a consistent response with an increase in growth and photosynthesis conferred by Ambiol to tomato seedlings under drought. This was similar to previous studies with tomato seedlings (MacDonald et al, 2008(MacDonald et al, , 2009 as well as other species (Darlington et al, 1996;Islam et al, 2003;Rajasekaran and Blake, 2002) involving other species. Typically, a decrease in transpiration has also been reported in other species, which has often been linked to the drought-mitigating effects of Ambiol.…”

“…Recent advances have also found that Ambiol is very effective at promoting drought tolerance in tomato seedlings and have focused on understanding the regulatory pathway of Ambiol. MacDonald et al (2008, 2009 reported that preconditioning with 10 mgÁL -1 Ambiol increased root growth, shoot growth, leaf expansion, photosynthesis, and water use efficiency (WUE) in tomato seedlings under drought stress. It was also found that Ambiol preconditioning invokes certain proteins in the seed, both before and after germination.…”

“…It was also found that Ambiol preconditioning invokes certain proteins in the seed, both before and after germination. It was proposed that Ambiol preconditioning first alters the expression of certain genes, sending an (as of yet) unknown signal(s) to elicit a response in the form of membrane protection and increased growth (MacDonald et al, 2009).…”

“…If it is understood that ABA regulates stomatal aperture to protect plants from drought, is ABA necessary for Ambiol to induce drought tolerance? From the results of MacDonald et al (2008MacDonald et al ( , 2009, it remains unclear whether the mode of action of Ambiol in promoting drought tolerance requires the presence of ABA or is independent of ABA, but as a result of similarities in the effects of ABA and Ambiol, it was hypothesized that ABA is required for Ambiol action to enhance drought tolerance. If this is so, inhibiting ABA synthesis will negate the beneficial effects of Ambiol.…”

Physiological and sanitary quality of maize seeds preconditioned in ozonated water

“…Physiological conditioning is a technique of controlled hydration of seeds, which allows the activation of the metabolic processes of germination and avoids primary root production, favoring uniformization and better performance of the plants in the field (MacDonald & Lada, 2009). This technique allows the use of reserves and synthesis of metabolites necessary to germination, leading to faster seed germination, reducing the time of exposure to unfavorable conditions, such as attacks by microorganisms and water deficit, among others (Marcos Filho, 2015).…”