Apoplastic and symplastic solute concentrations contribute to osmotic adjustment in bean genotypes during drought stress

Neslihan SARUHAN GÜLER, Aykut SAĞLAM, Mehmet DEMİRALAY, Asım KADIOĞLU
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Abstract


The present study investigates changes in the inorganic ions, proline, and endogenous abscisic acid (ABA) contents of the apoplastic and symplastic compartments of leaves from drought-tolerant (Yakutiye) and drought-sensitive (Zulbiye) cultivars of the common bean (Phaseolus vulgaris L.). Drought stress caused a decrease in leaf water potential and stomatal conductance in both cultivars. Concentrations of proline in the drought-tolerant and drought-sensitive cultivars increased in response to drought stress in both compartments. The symplastic K+ concentration decreased in both cultivars. However, the opposite trend was observed concerning K+ concentrations in the apoplastic areas. While the symplastic Na+ concentrations significantly decreased in the drought-tolerant cultivar, the apoplastic Na+ concentrations increased during drought stress. However, Na+ concentrations did not significantly change in either of the compartments in the drought-sensitive cultivar. The Ca2+ concentrations in the sensitive cultivar significantly decreased in both compartments during drought stress. In the tolerant cultivar, the Ca2+ concentration significantly increased in the symplast but decreased in the apoplast. Cl- concentrations in the tolerant cultivar did not significantly change in either compartment. In the sensitive cultivar, the Cl- concentration increased in the apoplastic area but decreased in the symplastic area. In addition, while the symplastic sap of the leaves exhibited a constant pH value, it diminished in the apoplast during drought stress. Symplastic and apoplastic ABA concentrations significantly increased in both cultivars. It might be said that inorganic ions (especially Na+, K+, and Ca2+) and ABA concentrations changed between the apoplastic and symplastic spaces to contribute to osmotic adjustment under drought stress. In addition, the drought-tolerant cultivar showed a much higher capacity to maintain osmotic adjustment between the symplast and the apoplast.

Keywords


Key words: Apoplast, symplast, drought stress, tolerance, inorganic ions, abscisic acid

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