Antioxidant defense response of fenugreek to solar UV

• Published in: International journal of vegetable science 2019-01, Vol.25 (1), p.40-57
• Main Authors: Sharma, Sonika, Kataria, Sunita, Joshi, Juhie, Guruprasad, K. N.
• Format: Article
• Language: English
• Subjects: antioxidant enzymes; Antioxidants; Ascorbic acid; Cages; Crop yield; Detoxification; Energy metabolism; Enzymes; Fenugreek; Filters; growth; Guaiacol; Iron; Leaf area; Leaves; Malondialdehyde; Metabolism; Peroxidase; Plant growth; Polyethylene; Polyethylenes; Reactive oxygen species; Scavenging; Solar energy; Solar radiation; solar UV (280-400 nm); Superoxide dismutase; Trigonella foenum-graecum; Tropical environments; Ultraviolet radiation; Weight; yield
• ISSN: 1931-5260; 1931-5279
• DOI: 10.1080/19315260.2018.1466844

In the tropics, solar UV-B background level is often high and can affect growth and development of vegetables. Fenugreek (Trigonella foenum-graecum L.), which is not native to India, may be detrimentally affected by solar ultraviolet (UV). This UV radiation-impacting plants can affect defense system by activating, or elevating, antioxidant enzymes. The study was undertaken to determine physiological and defensive responses of fenugreek to solar UV from 280 to 400 nm. The UV-B and UV-B+A were excluded with appropriate filters to assess effects of UV-B radiation under field conditions. Plants were grown in iron mesh cages covered with filters to specifically exclude UV-B (280-315 nm) or UV-B+A (280-400 nm) solar radiation. Control plants were grown under polyethylene filters transmissible to solar UV. Exclusion of solar UV enhanced plant height, leaf area, and fresh and dry weight of plants compared to the control. Exclusion of UV-B and UV-B+A decreased levels of antioxidants ascorbic acid (ASA), malondialdehyde, and activities of the antioxidant enzymes superoxide dismutase, ASA peroxidase, and guaiacol peroxidase in leaves compared to the control. There was a reduction in UV absorbing substances (UAS) after solar UV exclusion. The overall decrease in levels of antioxidants and antioxidant enzymes by solar UV exclusion demonstrates that ambient UV components exert detrimental effects and can potentially reduce growth and yield of fenugreek. Reduced amount of UAS and antioxidant enzymes in UV-excluded plants indicates that plants do not have to divert metabolic energy in detoxification of reactive oxygen species (ROS) produced due to exposure to solar UV. The metabolic energy required for scavenging these ROS was efficiently utilized toward maintaining growth of plants and improved the crop yield under exclusion of ambient UV conditions.