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Research project (§ 26 & § 27)
Duration : 2021-11-01 - 2025-10-31

The impact of heat on plants is intrinsically tied to plant water use. Heatwaves have more than tripled, warmed by 2.3K and usually combine with drought. Under heat, stomata act at the leeway between cooling and critical water loss. Once they close, cooling ceases, leaf overheating boosts transpiration and water loss across cuticles becomes decisive. Unfortunately, permeance of cuticles rises exponentially with heat. Little is known about the structural basis of changes, whether increased cuticular transpiration is reversible and acclimation is possible. Also the tolerance to various heat doses and effect on cuticular transpiration is largely unknown. To close these knowledge gaps plants in temperate alpine vs. tropical habitats are compared, experiencing different heat doses (intensity x duration). Thereby the following questions will be addressed: What are the habitat-specific heat doses, leaf to air temperature differences and vapor pressure deficits? Does heat dose affect heat survival? Which heat dose, vapor pressure deficits and plant water potential closes stomata? How does cuticular transpiration respond to various heat doses and vapor pressure deficits? Are heat-induced changes of cuticular transpiration reversible? Does heat exposure alter cuticle structure? Does excess water loss explain heat damage? So the project explores the reversibility and acclimation potential of heat treshold of cuticular transpirationt by different approaches. To get insights into the cuticle of plants from cold vs. hot habitats RAMAN microscopy and transmission electron microscopy will be applied. Reaching from laboratory to the field and from molecules to individuals, the study promises comprehensively new insights into heat survival of plants. Results will be important to assess the future heat risk to plants in a globally warmer world.
Research project (§ 26 & § 27)
Duration : 2021-08-01 - 2025-07-31

Freezing events significantly impair plant life. Biophysical aspects of freezing are less studied than molecular responses but are fundamental to the understanding of freezing resistance. During harmless freezing of plant tissues ice accumulates extracellularly and cells usually freeze dehydrate. How ice growth is controlled and how cellular water is segregated to the ice is not understood. As plants consist in large part of water, the amount of ice formed must be considerable. While reduction of water content is part of cold acclimation, spring and alpine plants survive freezing with high water content. Hardly anything is known about how the growing ice masses are managed. There is, however, recent evidence that ice accumulates in predetermined spaces. Some of them seem to pre-exist, others are formed by tissue rupture. We hypothesize that 1) The spatial confinement of ice masses must be managed by targeted ice segregation at specific loci. 2) Ice masses show a temperature dependent growth and 3) ice mass growth is regulated by ice affecting molecules that locally promote or inhibit ice mass formation, facilitate targeted ice segregation and affect ice crystal morphology. With a new set of new and innovative methods we tackle the biophysical and chemical aspects of ice growth in plant tissue: (1) A new cryo-microscope using reflected-polarised-light (CMrpl) allows an unambiguous and rapid visualisation of ice masses and the analysis of ice crystal shape and their attachment to cell walls. (2) Recent results obtained with a new calorimeter (µDSC 7 Evo) uncover till now invisible very slight freezing processes in leaves. 3) By GC-MS molecular components of ice crystals and by RAMAN microscopy also molecular components of cell walls and cell lumina close to ice will be revealed.
Research project (§ 26 & § 27)
Duration : 2019-01-01 - 2021-12-31

Carbon nano tubes (CNTs) are cylindrical nano structures made of carbon atoms. Due to their outstanding mechanical and electrical properties, and thermal conductivity, they are already used as additives in various novel materials. Recently, CNTs have also been considered for several medical applications due to their small diameters and ability to penetrate cells and tissues. However, since CNTs are chemically inert and insoluble in water, they have to be chemically functionalized or coated with biomolecules to carry payloads or interact with the environment. Proteins bound to the surface of CNTs are preferred because they provide a better biocompatibility and offer functional groups for binding additional molecules. Nevertheless, their arrangement and density on the CNT surface and, consequently the availability of functional groups, varies considerably. An alternative approach to functionalize CNTs with an - additionally closed and precisely ordered - protein layer is offered by bacterial surface layer (S-layers) proteins which have already attracted much attention in the functionalization of surfaces as well as supporting structures for biomembranes. In a broad range of bacteria and archaea S-layer proteins cover the cells completely and may be considered as one of the most abundant biopolymers on earth. S-layer protein lattices show parameters in the nanometer range and offer surface chemical groups and genetically introduced biologically functional domains in precisely defined locations and orientation on their surfaces. Moreover, and highly relevant for this project too, is the natural capability of isolated S-layer proteins to self-assemble into monolayers in solution and at interfaces (e.g. on solid supports). The overall project aim is to conduct fundamental studies on the reassembly of S-layer proteins on CNTs and learn from nature how these new hybrid architectures may be used to make novel materials e.g. for biosensing. Key are the reassembly and binding properties of S-layer proteins which allow a highly specific and sensitive functionalization of the CNT surface. Moreover, novel hybrid organic-inorganic nano structures (e.g. nano containers for drug delivery) will become possible by using the S-layer coating as template in the biomineralization of silica, metals or other technologically important materials. Further on, it may also be assumed that the pores in the S-layer lattice will induce an ordered arrangement of metallic nanoparticles directly on the CNT surface and thus might lead to new electronic effects along the “one-dimensional” CNTs. Based on these few examples of an S-layer protein and CNTs construction kit, we would like to stress that our research, although longer term in nature, might lead to a new technology for the functionalization of carbon nanotube surfaces.

Supervised Theses and Dissertations