The use of aeroponics to investigate antioxidant activity in the roots of Xerophyta viscosa

Abstract

In order to ultimately understand the whole plant mechanism of attaining desiccation tolerance, we undertook to investigate the root tissues of the resurrection plant Xerophyta viscosa, as previous work has only been conducted on the leaf tissues of resurrection plants. An aeroponic plant growth system was designed and optimised to observe the root's response to desiccation without the restrictions of a soil medium, allowing easy access to roots. Successful culture of both X.viscosa and the control, Zea mays, was achieved and dehydration stress was implemented through reduction of nutrient solution spraying of the roots. After drying to the air dry state (achieved after 7 days for roots and 10 days for shoots), rehydration was achieved by resumption of root spraying. X.viscosa plants survived desiccation and recovered but Z. mays did not. The activity of the antioxidant enzymes superoxide dismutase, catalase, ascorbate peroxidase and glutathione reductase and quantities of ascorbate and glutathione were determined during root desiccation. There was an initial decline in activity in all enzymes upon drying to 80% RWC, but activity thereafter remained constant, at rates indicative of potential metabolic activity, to the air-dry state. This data suggests that these enzymes are not denatured by desiccation of the root tissue. Ascorbate and glutathione content remained constant at concentrations of 70 and 100 lM, respectively during drying. Thus root tissues appear to retain antioxidant potential during drying, for use in recovery upon rehydration, as has been reported for leaf tissues of this and other resurrection plants.

A Systems‐Based Molecular Biology Analysis of Resurrection Plants for Crop and Forage Improvement in Arid Environments

“…It has shown that transcription of a recently discovered gene encoding an enzyme essential to ascorbic acid biosynthesis, in the resurrection plant X. viscosa, is upregulated when the plants are dried below 60% relative water content and that mRNA levels remain high in the desiccated plant and during early stages of rehydration. Ascorbate levels in roots and leaves of this plant follow the same trend [46] and we propose that elevated ascorbate levels are maintained during drying and early rehydration by a combination of de novo synthesis and regeneration of ascorbate [14,46]. Further to the standard housekeeping antioxidants, resurrection plants have the ability to induce, de novo, antioxidants such as 1-and 2-cys-peroxiredoxins, glyoxylase I family proteins, and zinc metallothionine and metallothionine-like antioxidants in response to desiccation [14,34,47,48].…”

Modern plant cultivation technologies in agriculture under controlled environment: a review on aeroponics

“…However, the plant grows speedily in the system due to the sterile environment and abundant oxygen availability in the growth chamber. However, several research studies practiced the modern plant growing technology for the cultivation of horticultural ornamental, the root of herbs and root based medicinal plants production (Clayton and Lamberton 1964;Cho et al 1996;Park and Chiang 1997;Burgess et al 1998;Garrido et al 1998a;Garrido et al 1998b;Scoggins and Mills 1998;Molitor et al 1999;Kamies et al 2010). Stoner (1983) reported that before 1966s the aeroponics system was performed only as a laboratory analysis to investigate the plant root structure.…”

Editorial: special issue GROW “plant desiccation stress”

“…Typically such studies pose specific research questions and are conducted using discipline specific approaches on a single species, but often reflect some common questions and strategies associated with research into desiccation tolerance. Papers within this issue report on stresses associated with water deficit, such as the mechanical stress of plasmolysis (Koster et al 2010), oxidative stresses, including those associated with light (Aidar et al 2010;Proctor 2010;Kamies et al 2010;Colville and Kranner 2010) and the protective responses generated in response to those stresses, or take a more global approach of searching for genes and gene products up regulated in response to stress (Abdalla et al 2010). In addition to furthering our understanding of stresses and associated protection these works add important information to the field.…”

“…Proctor (2010) utilizes chlorophyll-fluorescence parameters to compare and quantify recovery responses in a range of bryophytes and pteridophytes and proposes that this tool can give insight into factors influencing recovery time and rate. Kamies et al (2010) describe the successful use of aeroponics to study antioxidant responses of roots of the resurrection plant Xerophyta viscosa to desiccation. There are few studies reported on roots of resurrection plants largely due to the problems associated with adherence of soil and associated microbes which cannot be removed from dry roots without altering tissue water content.…”

“…Due to lack of funding, extensive and varied technological requirements and/or adequate personnel with requisite expertise, such endeavours are often not possible. Researchers from the University of Cape Town, South Africa are following such an approach on species from the genus Xerophyta, and two papers within this issue (Kamies et al 2010;Abdalla et al 2010) bear testimony of some of their endeavours. In Myers et al (2010), the authors examine the role of desiccation and other environmental cues involved in regulation of flowering in X. humilis; this work being an example of some of the ecological research being undertaken by the group.…”