Mitteilungen der Gesellschaft für Pflanzenbauwissenschaften Band 23

Mitt. Ges. Pflanzenbauwiss. 23: 188 (2011)
Effect of Ca supply on cytosolic pH and Ca in leaves of wheat
plants growing under NaCl stress
Sherif H. Morgan 1,2,3 , Sylvia Lindberg 2 and Karl H. Mühling 1
1 Institute for Plant Nutrition and Soil Science, Christian-Albrechts-University, Kiel, Germany; 2 Botany
Department, Stockholm University, Stockholm, Sweden; 3 Plant Physiology Section, Plant Botany
Department, Faculty of Agriculture, Cairo University, Giza, Egypt. E-Mail: dr.morgan77@yahoo.com
Introduction
Calcium maintains the cell wall and membranes structures as well as many other
physiological processes. Also Ca influence both growth and, as a ubiquitous second
messenger in plants, Ca influencing the plant responses to stress. Perception of salt
stress in plant cells induces a change in cytosolic Ca, [Ca 2+ ]cyt, Na + , [Na + ]cyt and pH,
[pH]cyt, which in resistant cultivars transfers downstream reactions toward salt
resistant [1]. Upon short-term salt stress (minutes or hours) there are transient shifts
in [Ca 2+ ]cyt and pHcyt but little is known about the long-term effects (days) by salinity
on [Ca 2+ ]cyt and [pH]cyt levels. Therefore, we focused on measuring the [Ca 2+ ]cyt and
[Na + ]cyt concentrations and [pH]cyt to investigate if a relation existed between changes
in [Ca 2+ ]cyt and [pH]cyt in response to external supplied Ca 2+ and/or NaCl approaching
to have more clear vision to understand the behaviour of the plant under salinity.
Materials and Methods
The effect of salinity (0 and 50 mM NaCl) was investigated on wheat seedlings cv.
Seeds1 during 7 d of cultivation in hydroponics, with and without extra Ca addition (0
and 5 mM CaSO4). Protoplasts were isolated by an enzymatic method [2] and Fura2-
AM, SBFI-AM and BCECF-AM were loaded for detecting [Ca 2+ ]cyt [3], [Na + ]cyt [4] and
[pH]cyt [2], respectively, using fluorescence microscopy. Data were statistically
analyzed using two factorial completely randomized design (CRD) and means were
compared using the least significant difference test (L.S.D.) at 5% level of probability.
Results and Discussion
Less Ca 2+ was taken up into the cytosol of leaf protoplast under salinity when
compared with control plants. While contrarily was reported with extra Ca 2+ addition
only at saline condition, which could indicate that, the long-term changes of [Ca]cyt
level are both salinity and Ca dependant. Moreover, irrespective of Ca 2+ treatment,
the [pH]cyt increased upon salinity treatment, while [Na]cyt did not change significantly.
References
1. Kader MA, Lindberg S. 2010: Cytosolic calcium and pH signaling in plants under salinity stress.
Plant Signaling Behavior 5(3):233-238.
2. Lindberg S, Strid H. 1997: Aluminium induces rapid changes in cytosolic pH and free calcium and
potassium concentrations in root protoplasts of wheat (Triticum aestivum). Physiol Plant 99:405-14.
3. Shishova M, Lindberg S. 2004: Auxin induces an increase of Ca 2+ concentration in the cytosol of
wheat leaf protoplasts. J Plant Physiol 161:937-945.
4. Kader MA, Lindberg S. 2005: Uptake of sodium in protoplasts of salt-sensitive and salt-tolerant
cultivars of rice, Oryza sativa L. determined by the fluorescent dye SBFI. J Exp Bot 56:3149-3158.