Browsing by Person "Franzisky, Bastian Leander"

Now showing 1 - 2 of 2

Aspects of stomatal physiology during salt-stress-related disturbances of ion homeostasis
(2020) Franzisky, Bastian Leander; Zörb, Christian
Soil salinity is a major challenge for agriculture, because most crop plants are sensitive to high salt concentrations in soil, an environment that results in reduced growth and yield. One major constraint imposed by salinity is the disruption of ion homeostasis attributable to the uptake competition of salts and nutrients and the accumulation of deleterious ions, which are toxic to plants at high concentrations. For a better understanding of ion-homeostasis-associated traits contributing to salt tolerance in salt-sensitive crops, such as Vicia faba and Zea mays, the capabilities of ion exclusion and tissue tolerance were assessed in diverse genotype selections under saline conditions. In addition, the impact of increased salt ion concentrations in leaves and in the apoplast on stomatal physiology and guard cell integrity was characterized in V. faba exposed to long term salinity in order to improve our knowledge of stomatal physiology and functioning under conditions of NaCl stress. The treatment of diverse V. faba varieties with 100 mM NaCl demonstrated that ion homeostasis-associated tolerance mechanisms are differentially managed for Na+ and Cl-. 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 summary, this work shows 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.
Local and systemic metabolic adjustments to drought in maize: hydraulic redistribution in a split‐root system
(2022) Werner, Lena Maria; Hartwig, Roman Paul; Engel, Isabelle; Franzisky, Bastian Leander; Wienkoop, Stefanie; Brenner, Martin; Preiner, Julian; Repper, Dagmar; Hartung, Jens; Zörb, Christian; Wimmer, Monika Andrea
Background: It is yet unknown how maize plants respond to a partial root drying under conditions of a limited total water supply, and which adaptation mechanisms are triggered under these conditions. Aims: The aims of this study were to assess whether partial root drying results in distinguishable local and systemic physiological and metabolic drought responses, and whether compensatory water uptake and/or alteration of root architecture occurs under these conditions. Methods: Maize plants were grown in a split-root system. When plants were 20 days old, the treatments ‘well-watered’, ‘local drought’ and ‘full drought’ were established for a period of 10 days. Shoot length and gas exchange were measured non-destructively, root exudates were collected using a filter system and biomass, relative water content, osmolality and proline content were determined destructively at final harvest. Results: Local drought triggered stress responses such as reduced biomass, shoot length, relative water content and increased osmolality. Maintained root growth was systemically achieved by hydraulic redistribution rather than by altering root architecture. Local and systemic osmolyte adjustments contributed to this hydraulic redistribution. Conclusions: Both local and systemic metabolic responses helped the plants to induce hydraulic redistribution, enhance water availability and in consequence plant water relations. This resulted in a surprisingly well-maintained root growth even in the drought stressed root compartment.