JXB Advance Access originally published online on September 21, 2006
Journal of Experimental Botany 2006 57(14):3707-3715; doi:10.1093/jxb/erl120
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© 2006 The Author(s).
This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/2.0/uk/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.This paper is available online free of all access charges (see http://jxb.oxfordjournals.org/open_access.html for further details)
RESEARCH PAPER |
The role of abscisic acid and low temperature in chickpea (Cicer arietinum) cold tolerance. II. Effects on plasma membrane structure and function
1Department of Agronomy, NWFP Agricultural University, Peshawar, Pakistan
2Department of Biological Sciences, Quaid-E-Azam, University of Islamabad, Pakistan
3Plant Science Group, Division of Biochemistry and Molecular Biology, Institute of Biomedical & Life Science, University of Glasgow, Glasgow G12 8QQ, UK
* To whom correspondence should be addressed. E-mail: p.dominy{at}bio.gla.ac.uk
The frost hardiness of many plants such as chickpea can be increased by exposure to low non-freezing temperatures and/or the application of abscisic acid (ABA), a process known as frost acclimation. Experiments were conducted to study the response over a 14 d period of enriched plasma membrane fractions isolated from chickpea plants exposed to low temperature and sprayed with exogenous ABA. Measurement of the temperatures inducing 50% foliar cell death (LT50), and subsequent statistical analysis suggest that, like many plants, exposure to low temperatures (5/–2 °C; day/night) induces a significant level (P <0.05) of frost acclimation in chickpea when compared with control plants (20/7 °C; day/night). Spraying plants with exogenous ABA also increased frost tolerance (P <0.05), but was not as effective as low temperature-induced frost acclimation. Both pre-exposure to low temperatures and pre-treatment with ABA increased the levels of fatty acid desaturation in the plasma membrane (measured as the double bond index, DBI). Exposure of chickpea plants to low temperatures increased the DBI by 15% at day 4 and 19% at day 14 when compared with untreated control plants. Application of ABA alone did not increase the DBI by more than 6% at any time; the effects of both treatments applied together was more than additive, inducing a DBI increase of 27% at day 14 when compared with controls. There was a good correlation (P <0.05) between the DBI and LT50, suggesting that the presence of more unsaturated lipid in the plasma membrane may prevent cell lysis at low temperatures. Both pre-exposure to low, non-freezing temperatures and pre-treatment with ABA induced measurable changes in membrane fluidity, but these changes did not correlate with changes in LT50, suggesting that physical properties of the plasma membrane other than fluidity are involved in frost acclimation in chickpea.
Key words: ABA, abscisic acid, low temperature, double bond index, LT50, plasma membrane fluidity