Abstract
Asplenium ceterach belongs to a group of poikilohydric ferns and it can recover uninjured from an almost completely dehydrated state. In our study, short term dehydration (24h) at four different water potentials, resulted in moderate water loss (partial desiccation) in fern tissue. The main phenolic acids represented in A. ceterach were chlorogenic (CGA) and caffeic acid (CA) and their content decreased during the dehydration process. For the first time, peroxidase (POD) and polyphenol oxidase (PPO) isoforms were determined in the rustyback fern. The results exhibit the presence of numerous anionic POD isoforms, with pI ranging from 4.4 to 5.8, but none of the cationic isoforms was detected. Two PPO isoforms were identified, one anionic with pI 6.3 and one cationic with pI of about 9.0. Short-term dehydration brought about a remarkable increase in POD and PPO activity using CGA as a substrate. Changes in enzyme activity and content of substrates during dehydration may play an important role in the adaptation of the rustyback fern to water deficit, and increase the overall plant resistance to stress conditions.
Highlights
Certain plant species, termed desiccation-tolerant or resurrection plants, have evolved the remarkable ability to withstand extreme dehydration and rapid rehydration of vegetative tissues without cell damage
During dehydration treatment the CGA content significantly decreased from 9.5 mg g-1 dry weight (DW) at a water potential of ψ=-1 MPa to 5.3 mg g-1 DW at a water potential of ψ=-4 MPa, showing an approximately 2-fold decrease compared to the control (Fig. 2B)
The content of caffeic acid (CA) changed with dehydration reaching a 2-fold greater decrease as compared to the control during the dehydration process, with no significant differences between the single treatments
Summary
Certain plant species, termed desiccation-tolerant or resurrection plants, have evolved the remarkable ability to withstand extreme dehydration and rapid rehydration of vegetative tissues without cell damage. The number of environmental stresses, including water-deficit stress, could disrupt normal metabolism in plants and cause (initiate) oxidative damage as a secondary effect (Smirnoff, 1993). Desiccation-tolerant plants have a well-developed defense system that involves the reduction of metabolic activities, thereby slowing down the production of ROS (Navari-Izzo et al, 1997; Sgherri et al, 1996). In angiosperms these protection mechanisms, among the rest, include controlled loss/retention of chlorophyll (Proctor & Tuba, 2002; Farrant et al, 2003) and the accumulation of various antioxidant protectants for the quenching the ROS (Kranner & Birtić, 2005). Plant cells utilize an integrated system of enzymatic and non-enzymatic antioxidants to ensure the efficient removal of ROS under both normal and adverse environmental conditions (Grace et al, 1998)
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