Elsevier

Plant Science

Volume 166, Issue 2, February 2004, Pages 293-302
Plant Science

Effects of different irradiance levels on some antioxidant enzymes and on malondialdehyde content during rewatering in olive tree

https://doi.org/10.1016/j.plantsci.2003.09.018Get rights and content

Abstract

The effects of water recovery on the activities of superoxide dismutase (SOD; EC 1.15.1.1), catalase (CAT; EC 1.11.1.6), ascorbate peroxidase (APX; EC 1.11.1.11), guaiacol peroxidase (POD; EC 1.11.1.7), polyphenol oxidase (PPO; EC 1.30.3.1) and lipoxygenase (LOX; EC 1.13.11.12), and on malondialdehyde (MDA) levels were investigated in 2-year-old Olea europaea L. (cv. “Coratina”) plants grown in environmental conditions characterized by high temperatures and irradiance levels and gradually subjected to a controlled water deficit. After reaching the maximum level of water stress, plants were subjected to a rewatering treatment for 30 days, under both environmental irradiance and semi-shade conditions. The activities of SOD, CAT, APX, POD and LOX, and MDA levels decreased during the rewatering period in both leaves and roots and these decrements were faster in plants rewatered in semi-shade conditions (SHP) than in plants under environmental light (NSHP). In contrast, PPO activity increased during rewatering in both leaf and root tissues. Thus, the lower expression of the enzymatic antioxidant system in SHP with respect to NSHP may be due to a reduced need of activated oxygen species removal. On the contrary, in NSHP, higher enzyme activities are required for a better protection against a more pronounced oxidative stress.

Introduction

The response of plants to water stress is a species- and cultivar-dependent characteristic. In Mediterranean ecosystems, in which the summer months are characterized by elevated temperatures, high irradiance levels and lack of precipitation, plants are subjected to a continuous and severe water deficit [1]. Under these adverse environmental conditions, photoinhibition, photooxidation and photorespiration occur [2], [3].

Plants are particularly susceptible to photoinhibition when exposed to bright light [4], [5], [6] and environmental stresses as drought [7], chilling [8], [9] and heat [10]. The synergic action of high irradiance level and water stress reduces the capacity of the photosynthetic systems to utilize incident radiation, leading to a higher degree of photodamage [2], [11]. Under environmental conditions, where the photon energy is in excess of CO2 assimilation, photosystem II (PSII) is the primary target for photoinhibition, while PSI is more stable than PSII, receiving a damage usually less significant and strictly related to the rate of electron flow from PSII and the presence of oxygen [12], [13], [14].

The limitation of CO2 assimilation in water-stressed plants causes the over-reduction of photosynthetic electron chain. This excess of reducing power determines a redirection of photon energy into processes that favour the production of activated oxygen species (AOS), mainly in the photosynthetic [15] and mitochondrial electron transport chains [16]. Being toxic for the cells, AOS are efficiently eliminated by non-enzymatic (α-tocopherol, β-carotene, phenolic compounds, ascorbate, glutathione) and enzymatic antioxidants [17], [18]. The enzymatic antioxidant system include superoxide dismutase (SOD; EC 1.15.1.1), which catalyzes the reaction from O2radical dot to H2O2, and catalase (CAT; EC 1.11.1.6), ascorbate peroxidase (APX; EC 1.11.1.11) and guaiacol peroxidase (POD; EC 1.11.1.7), which are able to detoxify the H2O2 produced [2].

All the enzymes mentioned above exist in plant tissues in multiple forms. The three known types of SOD are classified by their metal cofactor and are mainly located in chloroplasts, cytosol and mitochondria [12], [19]. APX isozymes are generally located in chloroplasts, but microsomal, peroxisomal and membrane-bound forms, as well as soluble cytosolic and apoplastic isozymes, also exist [18]. CAT isoforms are particularly abundant in the glyoxysomes and in the peroxysomes [20]. POD have vacuolar and apoplastic forms which can use a wide range of substrates [21], including indoleacetic acid (IAA), and are so involved in auxin catabolism [22]. Polyphenol oxidase (PPO; EC 1.30.3.1), a copper enzyme located in plastids, acts on phenols in the presence of oxygen, catalysing the oxidation of o-diphenols into o-chinones [23]. When the accumulation of AOS under water stress conditions exceeds the removing capacity of the antioxidant system, the effects of oxidative damage arise, including peroxidation of membrane lipids, destruction of photosynthetic pigments and inactivation of photosynthetic enzymes [17].

Lipoxygenases (LOX; EC 1.13.11.12), located in cytosol [24], microsomes [25], plasma membrane [26] and oil bodies [27], catalyse the dioxygenation of polyunsaturated fatty acids containing a cis,cis-1,4-pentadiene moiety, producing hydroperoxy fatty acids, which are highly reactive compounds, toxic to the cell. Different LOX isozyme forms are involved in many physiological processes such as flowering [28], seed germination [29], formation of flavours and aroma in plant products [30], plant growth and development [31], pigment bleaching, senescence, pest resistance, wound stress and biosynthesis of regulatory molecules such as traumatin and jasmonic acid, which have growth-inhibitory properties analogous to those of abscisic acid [24].

Malondialdehyde (MDA), a decomposition product of polyunsaturated fatty acids hydroperoxides, has been utilized very often as a suitable biomarker for lipid peroxidation [32], which is an effect of oxidative damage. Nonetheless, lipids are not the only targets for MDA action; in fact MDA damages DNA, forming adducts to deoxyguanosine and deoxyadenosine [33].

Olive (Olea europaea L.) is a sclerophyll tree species with a high degree of drought tolerance [34]. In olive tree, severe drought stress causes closure of stomata [35], inhibition of photosynthesis [7] and transpiration [36], reduction of gas exchange [37] and changes in root and canopy dynamics [38], [39], but little is known about the effects of water deficit on antioxidant enzyme activities and oxidative damage in this species. Olive tree is able to restore leaf water potentials (LWP) and chlorophyll fluorescence after rewatering, but the rapid recovery of tissue water status is often coupled to a non-recovery of leaf functionality that lasts several days and is correlated with the level of stress previously reached [7]. The persisting deficit in leaf gas exchange found in this species could not be imputed to the non-recovery of cell turgor but, as observed in other species, to other factors probably involving the biochemical [40], [41] and hormonal balance [42], [43]. A complete understanding of the biochemical and metabolic factors involved in olive tree’s defence strategies against drought stress is of paramount importance to crop improvement but is, at present, lacking. The aim of this study was to investigate the influence of different levels of irradiance on antioxidant enzymes and LOX activities and on MDA level in olive tree during rewatering. We hypothesize that semi-shade conditions could minimize the oxidative effect of the damage following a period of water stress.

Section snippets

Study site and experimental design

Trials were conducted on self-planted 2-year-old Olea europaea L. plants, cv. ‘Coratina’, measuring 130–150 cm in height. The study site was located at the ‘Pantanello’ Agricultural Experiment Station in Metaponto (southern Italy, Basilicata region—40°24′N, 16°48′E). The experimental period started on 3 July and ended on 22 August, 2001.

Olive plants grew uniformly outdoors in 0.016 m3 containers filled with a mixture of loam, peat and sand (in proportion of 1:1:1). Pots were covered with plastic

Environmental conditions and physiological parameters

The highest value of maximum temperature was 37.5 °C on 7/29 and the mean of all the daily maximum values was 32.6 °C; RH pattern showed the highest value (44.4%) on 8/22, with a mean of 29.2%; VPD range was between 2.2 (on 7/5) and 5.0 kPa (on 8/11), with a mean value of 3.6 kPa; PPFD level showed a slight decrement during the experimental period, especially in the last 3 days of the trial (Fig. 1).

The mean predawn LWP in CP was −0.34 MPa. LWP in SHP increased during the whole rewatering period,

Discussion

Rewatering treatment following the water stress phase produced a rapid increase in LWP both in SHP and NSHP paralleled by slower increases in photosynthetic gas exchange (Fig. 2B–E). The delay in recovery of photosynthetic rate during rewatering, more marked in NSHP, is probably due to a light-dependent inactivation of the primary photochemistry associated with PSII occurred during the previous water stress [7] or to the downregulation of electron transport, as recently underlined by Nogués and

Acknowledgements

We thank Dr. Giuseppe Montanaro for his help in LCA-4 use and Prof. Elvira Di Nardo for her contribution in statistical analysis. We are grateful to Antonio Ditaranto and Angelo Mossuto for technical assistance.

References (65)

  • D.F Hildebrand et al.

    Changes in lipoxygenase isozyme levels during soybean embryo development

    Plant Sci.

    (1991)
  • L.J Marnett

    Lipid peroxidation—DNA damage by malondialdehyde

    Mutat. Res.

    (1999)
  • H Aebi

    Catalase in vitro

    Methods Enzymol.

    (1984)
  • B Chance et al.

    Assay of catalases and peroxidases

    Methods Enzymol.

    (1955)
  • P.H Rubery

    Studies on indole acetic acid oxidation by liquid medium from crown gall tissue culture cells: the role of malic acid and related compounds

    Biochim. Biophys. Acta

    (1972)
  • T.M Lee et al.

    Changes in soluble and cell-wall-bound peroxidase activities with growth in anoxia-treated rice (Oryza sativa L.) coleoptiles and roots

    Plant Sci.

    (1995)
  • F Sitbon et al.

    Enhanced ethylene production and peroxidase activity in IAA-overproducing transgenic tobacco plants is associated with increased lignin content and altered lignin composition

    Plant Sci.

    (1999)
  • D Ryan et al.

    Biotransformation of phenolic compounds in Olea europaea L.

    Sci. Hortic.

    (2002)
  • O Faivre-Rampant et al.

    IAA-oxidase activity and auxin protectors in nonrooting, rac, mutant shoots of tobacco in vitro

    Plant Sci.

    (2000)
  • M Hrubcová et al.

    Effect of inhibition of phenylpropanoid biosynthesis on peroxidase and IAA-oxidase activities and auxin content in alfalfa suspension cultures

    Plant Physiol. Biochem.

    (2000)
  • A.L.S Lima et al.

    Photochemical responses and oxidative stress in two clones of Coffea canephora under water deficit conditions

    Environ. Exp. Bot.

    (2002)
  • S Nogués et al.

    Effects of drought on photosynthesis in Mediterranean plants grown under enhanced UV-B radiation

    J. Exp. Bot.

    (2000)
  • C.H Foyer et al.

    Photooxidative stress in plants

    Physiol. Plant

    (1994)
  • D.H Greer et al.

    Photoinhibition of photosynthesis in intact kiwifruit (Actinidia deliciosa) leaves. Changes in susceptibility to photoinhibition and recovery during the growth season

    Planta

    (1992)
  • K Angelopoulos et al.

    Inhibition of photosynthesis in olive trees (Olea europaea L.) during water stress and rewatering

    J. Exp. Bot.

    (1996)
  • K.A Solhaug et al.

    Seasonal variation of photoinhibition of photosynthesis in bark from Populus tremula L.

    Photosynthetica

    (1998)
  • F.C Lidon et al.

    Photoinhibition in chilling stressed leguminosae: comparison of Vicia faba and Pisum sativum

    Photosynthetica

    (2001)
  • R.D Law et al.

    Inhibition and acclimation of photosynthesis to heat stress is closely correlated with activation of ribulose-1,5-bisphosphate carboxylase/oxygenase

    Plant Physiol.

    (1999)
  • A Wingler et al.

    Photorespiration: metabolic pathways and their role in stress protection

    Philos. Trans. R. Soc. London B

    (2000)
  • C Bowler et al.

    Superoxide dismutase and stress tolerance

    Annu. Rev. Plant Physiol. Plant Mol. Biol.

    (1992)
  • J.M Anderson et al.

    Unifying model for the photoinactivation of photosystem II in vivo under steady-state photosynthesis

    Photosynth. Res.

    (1998)
  • K Asada

    The water–water cycle in chloroplasts scavenging of active oxygens and dissipation of excess photons

    Annu. Rev. Plant Physiol. Plant Mol. Biol.

    (1999)
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