Antioxidant capacity

Abstract

Plants cope several biotic and abiotic stresses during their germination and growth. Allelochemicals stress is most important and refers to the effects of secondary metabolites (produced by some plants) on growth of receptor plants. One of these effects is the oxidative stress, manifested as large production of free radicals. In receptor plants, high production of free radicals can lead to enhance activity of antioxidant enzymes and increase the synthesis of molecular antioxidants (glutathione, ascorbate, tocopherol or phenols). However, some soil allelochemicals generate a large imbalance in the oxidative status of plant cells, sometimes inhibiting the root growth and adversely affecting the survival of receptor plants. This oxidative stress can be assessed, measuring the antioxidant capacity [potential of a plant part to scavenge free radicals (deleterious for growth of receptor plants)]. Sensitive roots exposed to a soil allelochemical often have less antioxidant capacity than non-exposed ones. Antioxidant capacity should be measured using high sensitive and micro-scale protocols, because root samples are usually small. Exposure of roots to soil allelochemicals requires appropriate assay performance that should consider factors such as selection of representative receptor plant species, exposure to allelochemicals alone or in mixtures and laboratory (i.e. hydroponics, Petri dishes) or greenhouse designs (i.e. pot assays). In addition, the antioxidant capacity should be measured in roots exposed and non-exposed to allelochemicals. Root extracts can be prepared using buffer solutions, distilled water and eventually organic solvents (such as DMSO). This chapter provides assays for assessing the antioxidant capacity in plant roots.