José A. Hernández (CEBAS-CSIC, Murcia)
Salinity is one the major limiting environmental factors in crop production. Salt stress (NaCl) is known to affect a multitude of physiological and biochemical processes. There are two main negative effects of salt stress that influence plant growth and development: water deficit, imposed by the low external water potential, and ion toxicity associated with excessive Cl– and Na+ uptake.
Salt stress, in addition to the known components of osmotic stress and ion toxicity, is also manifested as an oxidative stress, and all of these factors contribute to its deleterious effects (Gueta-Dahan et al. 1997; Hernández et al. 1993, 1995, 1999, 2000, 2001; Barba-Espín et al., 2011). However, ion content and salt tolerance are not often correlated, and several studies indicate that acquisition of salt tolerance may also be a consequence of improving resistance to oxidative stress (Hernández et al. 1993, 1995, 1999, 2000, 2001, Streb and Feieranbed 1996, Gosset et al. 1996, Gueta-Dahan et al. 1997, Gómez et al. 1999).
The effect of salinity on plant growth is detected at short-term. For example, the addition of 70 mM NaCl produced a delay in the growth of pea plants. In control plants, leaf area had increased by 18.5% after 96 h of the growth period in relation to time zero of growth. However, in salt-treated plants leaf growth was interrupted by salt addition (Fig 1). After 8 h of recovery (post-stress, corresponding to 56 h), leaf growth was also restored, but it was delayed in relation to control plants (approx. 8.2 % of delay) (Fig 1).
Furthermore, NaCl produced a strong increase in lipid peroxidation [oxidative stress marker that was estimated by determining the concentration of thiobarbituric acid-reactive substances (TBARS)] after 8 h of stress (180% increases in relation to control plants) (Fig 2). Nevertheless, a rapid decrease was observed during the stress period, suggesting an adaptation to the stress conditions. Surprisingly, the TBARS again increased after 8 h of the recovery period (78% increase) (Fig 2), suggesting that plants could interpret the elimination of NaCl as other stress period during the first hours of recovery. During the post-stress period, TBARS progressively decreased, although after 48 h of recovery (corresponding to 96 h in Figure 2) this value was still 21 % higher than in control plants. During the first hours of both stress and recovery an increase in TBARS occurred, suggesting the occurence of an oxidative stress during these periods. Probably, the change of growth conditions (elimination of NaCl from hydroponic cultures) is perceived by plants as a hypoosmotic stress situation. Cazalé et al. (1998) reported that an oxidative burst is produced in tobacco cells in response to hypoosmotic stress. This oxidative burst could cause membrane lipid peroxidation and could explain the increase in TBARS observed at 8h of recovery.
For more information, please consult:
HERNANDEZ JA and ALMANSA MS (2002) Short-term effects of salt stress on antioxidant systems and leaf water relations of pea plants. Physiol Plant 115: 251-257.
- Barba-Espín, G., Clemente-Moreno, M.J., Álvarez, S., García-Legaz, M.F., Hernández, J.A. and Diaz-Vivancos, P. (2011) Salicylic Acid Negatively Affects The Response To Salt Stress In Pea Plants: Effects On PR1b And MAPK Expression. Plant Biol., 13, 909–917.
- Cazalé AC, Rouet-Mayer MA, Barbier-Brygoo H, Mathieu Y, Laurière C (1998) Oxidative burst and hypoosmotic stress in tobacco cell suspensions. Plant Physiol 116:659-669.
- Gómez JM, Hernández JA, Jiménez A, del Río LA, Sevilla F (1999). Differential response of antioxidative enzymes of chloroplasts and mitochondria to long-term NaCl stress of pea plants. Free Rad Res 31: S11-18.
- Gueta-Dahan Y, Yaniv Z, Zilinskas, BA, Ben-Hayyim G (1997) Salt and oxidative stress: similar and specific responses and their relation to salt tolerance in Citrus. Planta 203:460-469.
- Hernández JA, Corpas FJ, Gómez M, del Río LA, Sevilla F (1993) Salt-induced oxidative stress mediated by activated oxygen species in pea leaf mitochondria. Physiol Plant 89: 103-110
- Hernández JA, Olmos E, Corpas FJ, Sevilla F, del Río LA (1995) Salt-induced oxidative stress in chloroplast of pea plants. Plant Sci 105: 151-167.
- Hernández JA, Campillo A, Jiménez A, Alarcón JJ, Sevilla F (1999) Response of antioxidant systems and leaf water relations to NaCl stress in pea plants. New Phytol 141: 241-251.
- Hernández JA, Jiménez A, Mullineaux PM, Sevilla F (2000) Tolerance of pea (Pisum sativum L.) to long-term salt stress is associated with induction of antioxidant defences. Plant Cell Environ 23: 853-862.
- Hernández JA, Ferrer MA, Jiménez A, Ros-Barceló A, Sevilla F (2001) Antioxidant systems and O2.-/H2O2 production in the apoplast of Pisum sativum L. leaves: its relation with NaCl-induced necrotic lesions in minor veins. Plant Physiol 127: 817-831.
- Streb P, Feierabend J (1996) Oxidative stress-responses accompanying photoinactivation of catalase in NaCl-treated rye leaves. Bot Acta 109:125-132.