Mitteilungen der Gesellschaft für Pflanzenbauwissenschaften Band 23

Mitt. Ges. Pflanzenbauwiss. 23: 193 (2011)
Apoplastic Na + in Vicia faba leaves rises after salt stress –
Evidence for the Oertli hypothesis
Muhammad Shahzad, Christian Zörb and Karl H. Mühling
Institut für Pflanzenernährung und Bodenkunde, Kiel. E-Mail: khmuehling@plantnutrition.uni-kiel.de
Introduction
Salinity primarily affects plants by shoot-growth inhibition. It has been suggested that
the ability of salt sensitive plants to stack up more Na + in their leaf apoplast under
salinity leads to their reduced water status. Evidence relating extra-cellular salt
accumulation is still enigmatic and was focused under short term saline conditions.
Silicon (Si) as found to alleviate deleterious salt effect, its role in the leaf apoplast
under salinity was also examined.
Materials and Methods
Vicia faba was subjected to increasing levels of salinity 1, 50, 75 and 100 mM NaCl.
1 mM Si treatment was added with the full nutrient concentration in Si treated pots.
For apoplastic washing fluid (AWF) collection, 3 rd , 4 th , 5 th and 6 th paired leaves from
bottom of the plants were excised 10 d after reaching the maximum salinity level at
100 mM NaCl.
Results and Discussion
We observed drastic increase in Na + concentration in leaf apoplast with increasing
salinity levels. Si treatment significantly reduced Na + concentration in the leaf
apoplast at higher salinity treatment. In addition, Si was also found to improve Ca 2+
status in the leaf apoplast at high salinity level. In our study, though high Na + in the
leaf apoplast of field bean partially support Oertli’s hypothesis that extracellular salt
accumulation can lead to wilty leaves, plant growth reduction, and later cell death.
However, significant decrease in Na + concentration in the leaf apoplast but with no
difference in fresh weight under salinity by silicon addition is also noticeable. These
findings do not favour earlier premise that Na + in the leaf apoplast is responsible for
the decline in leaf growth.
References
Mühling, K.H., Läuchli, A. 2002: Effect of salt stress on growth and cation compartmentation in leaves
of two plant species differing in salt tolerance. J. Plant Physiol. 159:137-146.
Oertli, J.J. 1968: Extracellular salt accumulation, a possible mechanism of salt injury in plants. Agrochimica.
12:461-469.
Slabu, C., Zörb, C., Steffens, D., Schubert, S. 2009: Is salt stress of faba bean (Vicia faba) caused by
Na + or Cl - toxicity? J. Plant Nutr. Soil Sci. 172:644-650.