The Activity of the Antioxidant Defense System of the Weed Species Senna obtusifolia L. and its Resistance to Allelochemical Stress

Abstract

Senna obtusifolia L., a common weed in the tropical and subtropical regions of the world, is able to germinate under adverse environmental conditions, suggesting that this species has efficient stress-adaptation strategies. The aims of the present work were to examine the energy metabolism and the antioxidant defense system of the Senna obtusifolia L. during seed germination and initial growth, and the responses to allelochemical-induced stress. Respiratory activity, the activities of alcohol dehydrogenase (ADH), superoxide dismutase (SOD), catalase (CAT),guaicol peroxidase (POD), ascorbate peroxidase (APX), glutathione reductase (GR), lipoxygenase (LOX) and the content of malondialdehyde (MDA) and glutathione (GSSG and GSH) were measured. Shortly after seed imbibition, mitochondrial respiratory activity was active and the presence of SOD, CAT, GR and LOX activity in embryos, along with significant KCN-insensitive respiration, indicated that the production of reactive oxygen species (ROS) is initiated as soon as mitochondrial respiration resumes. Among the fourteen allelochemicals assayed, only coumarin significantly supressed the growth of S. obtusifolia seedlings. Although coumarin reduced the activities of CAT, POD and APX, the GSH, GSSG and MDA levels were not altered. Alpha-pinene, quercetin and ferulic acid did not modify the activity of the antioxidant enzymes or the contents of GSH, GSSH and MDA. Thus the antioxidant defense system of S. obstusifolia may be effective in counteracting the harmful effects of ROS generated during seed germination and initial growth in the presence of toxic allelochemicals.

Phytotoxic potential of Senna occidentalis (L.) Link extracts on seed germination and oxidative stress of Ipê seedlings

“…These findings are in agreement with previous studies that reported inhibition in the activity of antioxidant enzymes under allelopathic stress (Sunmonu & Van Staden ; Bazdar & Sadeghi ; Coelho et al . ). In fact, the joint action of allelochemicals and their effects on all Ipê species evidenced that the changes in redox metabolism limited plant growth as a whole.…”

“…The role of ROS as signallers of stress and oxidative damage can be intensified due to the action of allelochemicals, causing severe injury to organelles such as chloroplasts, peroxisomes and mitochondria (Coelho et al . ). Some terpenoids, such as α‐pinene, are able to cause oxidative stress in plasma membranes, often altering permeability and/or leading to breakage of the structural integrity (Singh et al .…”

Allelopathic Potential of Plant Aqueous Mixtures on Euphorbia heterophylla

“…The respiratory activity of primary roots was probably altered via cytochrome oxidase in the presence of S. bicolor stems mixture. However, the increase in KCN-insensitive respiration suggests that the consumption of non-mitochondrial oxygen was stimulated by activation of transient oxidases not linked to the mitochondrial electron chain, including NAD(P)H oxidase, amine oxidase, polyphenol oxidase, oxalate oxidase, peroxidase, and lipoxygenase [43]. These enzymes contribute to KCN-insensitive respiration, which accounted for only 37% of the total respiratory activity in the control.…”

Redroot Pigweed (Amaranthus retroflexus L.) and Lamb’s Quarters (Chenopodium album L.) Populations Exhibit a High Degree of Morphological and Biochemical Diversity

“…Many changes have been observed in the activities of antioxidant enzymes in different ecotypes of plants (Aziz and Larher, 1998). The efficacy of the antioxidant defense system can likewise lead to high tolerance to different climate (Coelho et al, 2017).…”