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Humboldt-Universität zu Berlin - Faculty of Life Sciences - Albrecht Daniel Thaer-Institute of Agricultural and Horticultural Sciences





1. Chlorine: plant nutrient and toxicant; chlorine cycle

2. Yield stability, salinity and quality of plant-based products

3. Significance of the apoplast for systemic signalling of nutrient availabilities, water- and drought-stress



                        Experimental greenhouse facilities at Berlin-Dahlem, HU Berlin.


1. Chlorine: plant nutrient and toxicant; chlorine cycle

Chloride (Cl), the anion of the halogen element chlorine, is a micronutrient for higher plants and a beneficial macronutrient ion. It is involved in photosynthesis, in osmoregulation and turgor regulation, and in elongation growth. Under conditions of excess of Cl in the environment, tissue concentrations can exceed well-tolerated levels in plants, whereupon development, yield and quality are affected. However, the way in which high concentrations of Cl impede growth by causing toxicities has only been sparsely studied.


The aim of this research program lies in understanding how excessive concentration of Cl (i) impair the structural integrity of sub-cellular structures and (ii) affect physiological processes, and how plants respond to survive. Specifically, we study how Cl-salinity is linked to dysfunctionalities in guard cell- and chloroplast-biology, as these structures are particularly relevant for yield formation and use efficiencies of growth factors like water and mineral nutrients.


Current projects inclue:

  • Chlorine cycle in agricultural and horticulture plant production systems
  • Induction of abscisic acid biosynthesis by high Cl in maize
  • Mechanisms of tolerance to Cl-salinity

Model postulating why excessive concentrations of Cl are toxic for the cell (Geilfus, C. M., 2018, Plant and Cell Physiology, 59, 877-886).


Incorporation of manures can lead to an accumulation of excessive Cl in soils in (semi)-arid regions where precipitation is insufficient to leach Cl away from the roots (Geilfus, C. M., 2019, Environmental and Experimental Botany, 157, 299-309).


2. Yield stability, salinity and quality of plant-based products

Controlled-environment horticulture (CEH) is an approach to facilitate optimal growing conditions throughout the development of the horticultural crops. Moreover, CEH allows shifting metabolic pathways towards the production and tissue accumulation of human-health promoting secondary plant metabolites, doing so by regulating controllable abiotic production factors (growth factors) such as nutrient availability, water availability or light intensity/quality.

One aim of our research is to study how plants respond mechanistically when being subjected to sub-optimal growing conditions in order to overcome these environmental constraints. Second, we aim to elucidate how this knowledge about those eco-physiological adaptations can be utilized in smart horticulture to (i) improve qualities of horticultural crops and to (ii) stabilize yield in the light of the changing climate. Research activities of the group are focused but not limited to greenhouse and open-field production of vegetables and medicinal plants.


Current projects inclue:

  • Food production in connected, mutually communicating production units



  • Enriching anthocyanin content in vegetables and medicinal plants


The purple human-health promoting plant pigments anthocyanins can be enriched in the leaves of Pak choi (Brassica rapa subsp. chinensis) via subjecting plants to a stress event (right). Non-stress control at the left.



3. Significance of the apoplast for systemic signalling of nutrient availabilities, salt- and drought-stress

The apoplast is an interconnected compartment comprising a thin water-film that alkalinizes systemically in response to environmental stimuli. The apoplastic pH does not only increase during pathogen-host-plant-interactions but also in response to salinity, drought or changing availabilities of nitrogen. This apoplastic pH event may regulate growth and adjust stomatal aperture. However, not much is known about the mechanisms that cause the leaf apoplast to alkalinize, nor how functional impact is conveyed downstream.


We are studying at both the cellular and tissue level how changes in e.g. nitrogen-, water- or NaCl-availability are perceived and communicated via the apoplastic path from the site of the trigger to distant organs. Moreover, we are particularly interested in elucidating how changes in the pH of the apoplast modulate adaptation reactions.


Current projects inclue:

  • Elucidation of the functional impact of changes in the apoplastic pH during Cl-stress
  • Interactions between water-stress and nitrogen assimilation


Working model postulating that the pH of the apoplast is a dynamic factor with functional impact under stress (Geilfus, C. M., 2017, Molecular Plant, 10, 1371-1386).