Research

Research

Overview

As a prerequisite for colonization of the mainland, plants developed lipophilic biopolymers forming the interface between the plant and the surrounding air and soil environment. Leaf and fruit surfaces are covered by cuticles and waxes, stem and root interfaces are formed by suberized cell walls. As main function lipophilic interfaces form efficient transport barriers protecting land-living plants from uncontrolled water loss and at the same time they protect living plant tissue from infection by pathogens.

Various aspects of our ongoing research are related to:

The function of plant cuticles as barriers for water transport across leaf surfaces

The role of leaf surfaces as habitats for epiphyllic microorganisms

The structure and function of suberized hypodermal and endodermal cell walls forming the soil/root interface

Methods established in our Lab:

Radio-labelled and pressure probe techniques for transport properties of leaves and roots

Gas chromatography and mass spectrometry for analysis of cuticular waxes and the biopolymers cutin, suberin and lignin

Molecular biological and biochemical approaches for analyzing suberin and cutin biosynthesis

Microbiological and molecular biological methods are used for the cultivation and analysis of epiphyllic microorganisms.

Fluorescence microscopy, transmission- and scanning electron microscopy for characterization of cutinized and suberized plant interfaces.

Structure and Formation of Suberin in Roots

Suberin in roots is deposited in the cell walls of the endodermis (Casparian bands) and the hypodermis forming apoplastic transport barriers between the soil and roots (Schreiber and Franke 2011). Using analytical techniques, such as gas chromatography and mass spectrometry, characterization of the chemical composition of endodermal and hypodermal root cell walls is carried out (Schreiber 2010). Elongases and P450 hydroxylases involved in suberin biosynthesis in Arabidopsis and rice roots are analysed by molecular biological and biochemical techniques (Ranathunge et al. 2011). In order to relate the chemical composition of endodermal and hypodermal root cell walls to their function as apoplastic transport barriers, radial transport of solutes (Ranathunge et al. 2011), water (Ranathunge and Schreiber 2011) and oxygen (Kotula et al. 2009) is measured in Arabidopsis and rice roots.

Water and Solute Transport across Plant Cuticles

The most important function of the plant cuticle is to prevent land-living plants from desiccation (Schreiber 2010). In addition cuticles reduce the leaching of organic and inorganic chemicals from the leaf interior (Schlegel et al. 2006), they are the first barrier for the uptake of foliar applied herbicides (Ballmann et al. 2011) and they represent mechanical barriers for pathogens (Krimm et al. 2005). All these aspects have in common, that they are closely related to cuticular transport properties. Investigation of cuticular permeability is carried out using intact leaves, isolated cuticular membranes and isolated and subsequently recrystallized cuticular waxes (Schreiber and Schönherr 2009). Arabidopsis (Panikashvili et al. 2011) and rice (Shi et al. 2011) are used analysing wax and cutin biosynthesis.

Leaf Surfaces as Habitats for Microorganisms

Leaf surfaces of plants growing in their natural environments are colonized by epiphyllic microorganisms like bacteria, yeasts and filamentous fungi. This leads to various interactions between epiphyllic microorganisms and leaf surfaces (Schulze et al. 2005). Epiphyllic microorganisms can alter physicochemical properties of leaf surfaces by increasing wettability of the hydrophobic, water-repellent leaf surfaces and they can increase cuticular permeability (Schreiber et al. 2005). This will improve living conditions of the leaf surface as a habitat for epiphyllic microorganisms, since availability of water and nutrients will be increased (Krimm et al. 2005).