Carvalho et al. 2015 (Conference Paper) Guzmania

Drought affects antioxidant enzyme activities in Guzmania monostachia (L.) Rusby ex Mez atmospheric plants

Author(s):—Victoria Carvalho, Maria Elizabeth Abreu, Helenice Mercier & Catarina Nievola in Benko-Iseppon, A.M.; Alves, M. & Louzada, R. (2015) An overview and abstracts of the First World Congress on Bromeliaceae Evolution. Rodriguésia 66(2): A1-A66.

Publication:— (2015).

Abstract:—During exposure to environmental stresses, plants undergo an excessive production of reactive oxygen species(ROS), which could lead to cell death. Cells have an antioxidant defense mechanism that prevents imbalance inROS concentration, composed by enzymes and non-enzymatic substances. Recently, ROS have been associatedwith signaling to activate defense mechanisms against abiotic stress. For instance, crassulacean acid metabolism(CAM) pathway allows for protection against drought stress. It is hypothesized that CAM also prevents excessive production of ROS by dissipating accumulated energy in chloroplasts, generated during drought stress. Thebromeliad Guzmania monostachia (L.) Rusby ex Mez is a C3-CAM facultative species, which performs CAMafter 7 days of exposure to drought during both atmospheric and tank-form stages. The objective of this study wasto assess the diurnal variation of antioxidant enzymes activities and of ROS production in atmospheric plants of G. monostachia after exposure to drought. Plants of G. monostachia were cultured in vitro for 6 months in a growchamber. The plants were subsequently transferred to trays containing substrate, which were kept in a controlledenvironment chamber until they reached approximately 4?5 cm in height. Plants were then submitted to drought,in which watering was suspended during 10 days. Control plants were watered daily during the same period.Plants were harvested every 4 hours, starting at 8:00 and ending at 4:00. Total ROS production and activitiesof superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase (APX) and glutathione reductase (GR)were quantified from leaf samples of 10 plants. Relative water content was 76% and 40% in control and droughtplants, respectively. ROS production was stable between 12:00 and 24:00 in both treatments. An increase in ROSstarted at 4:00 and peaked at 8:00, which may be related to the fact that the light period began two hours beforethe sampling time (6:00). Still, at 8:00, plants under drought stress showed significantly lower levels of ROSthan control plants. At that same period, drought plants had higher activity of SOD, APX and GR compared tocontrol, which may indicate that the stress conditions induced higher enzymatic action of the antioxidant system.Therefore, these enzymes may be protecting cells against the increased production of ROS in this period.

Keywords:—Superoxide Dismutase; CAM; Stress.