Unraveling salt stress effects in guard cells of salt stressed Vicia faba L genotypes that contrast in their degree to salt tolerance
Final Report Abstract
Soil salinity is a major challenge for agriculture, because most crop plants are sensitive to high salt concentrations in soil. We demonstrated that ion-homeostasis-associated tolerance mechanisms are differentially managed for Na+ and Cl- in Vicia faba. The longer-withstanding varieties were tolerant to the accumulation of Na+ suggesting that tolerance to Na+ predominantly occurred at the level of tissue tolerance after Na+ had entered the leaves. Conversely, tissue tolerance for Cl- was weak throughout all varieties suggesting that the tolerance to Cl- was facilitated instead by the restriction of the intrusion of Cl- into the plant’s shoots; this process might be crucial for the ability of V. faba to withstand NaCl salinity. The treatment of diverse Z. mays hybrids with mild and high doses of Cl- added to the soil revealed that most genotypes restricted Cl- root-to-shoot translocation. This suggests that Z. mays effectively prevents Cl- from entering the xylem and, thus, the acropetal transport of Cl-, thereby hindering harmful Cl- accumulations building up in the photosynthetically active leaf blades. A detailed analysis of guard cell physiology under long-term NaCl demonstrated that guard cell primary metabolism differentially responds to altered ion composition resulting from salt stress in comparison with whole leaf tissue in V. faba; such a differential response might be a prerequisite for the maintenance of guard cell functionality under conditions of stress, i.e. the adjustment of guard cell turgor that affects stomatal aperture and water loss. Moreover, the shift from a photoperiod-dependent accumulation of sucrose in guard cells and the apoplast to a photoperiod-independent under salinity suggests that a metabolic sucrose-mediated feedforward mechanism is involved in coordinating stomatal closure under conditions of long-term NaCl and might be beneficial for reducing water loss under conditions of stress-related carbon partitioning. In agreement with the anticipated stress and the increased sucrose content, the analysis of guard cell ultrastructure showed that the numbers of stromule and plastoglobuli increased in response to long-term salt stress. In summary, we demonstrated that ion-homeostasis-associated tolerance traits vary between crop species and that the differential metabolic acclimatisation of guard cells to disturbed ion homeostasis might represent an important aspect of tissue tolerance enabling the maintenance of stomatal regulation during long-term salinity.
Publications
- (2018). Early response to salt ions in maize (Zea mays L.). J. Plant Physiology 220, 173-180
Geilfus, C.-M., Ludwig-Müller, J., Bárdos, G., Zörb, C.
(See online at https://doi.org/10.1016/j.jplph.2017.11.010) - (2019). Ion-dependent metabolic responses of Vicia faba L. to salt stress. Plant, Cell, and Environment 42, 295-309
Richter, J.A., Behr, J.H., Erban, A., Kopka, J., Zörb, C.
(See online at https://doi.org/10.1111/pce.13386) - (2019). Salinity and crop yield. Plant Biol. 21, 31-38
Zörb, C., Geilfus, C.M., Dietz, K.J.
(See online at https://doi.org/10.1111/plb.12884) - (2019). Shoot chloride translocation as a determinant for NaCl tolerance in Vicia faba L. - Journal of Plant Physiology, 236, 23-33
Franzisky, B.L., Geilfus, C.-M., Kränzlein, M., Zhang, X., Zörb, C.
(See online at https://doi.org/10.1016/j.jplph.2019.02.012) - (2019). The early stress response of maize (Zea mays L.) to chloride salinity. Journal of Agronomy and Crop Science 205, 586-597
Zhang, X., Zörb, C., Kränzlein, M., Franzisky, B.L., Kaiser, H., Geilfus, C.-M.
(See online at https://doi.org/10.1111/jac.12356) - (2020). Improving crop salt tolerance using transgenic approaches: an update and physiological analysis. Plant, Cell & Environment
Kotula, L., Garcia, P., Zörb, C., Colmer, T. D., & Flowers, T. J.
(See online at https://doi.org/10.1111/pce.13865)
