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How does the productivity of plant populations vary with the frequency of water-wasting plants, and association with arb

Main supervisors: Prof. Ian T. BaldwinDr. Meredith Schuman, Department of Molecular Ecology, MPI-CE
Co-supervisor(s): Prof. Nicole Van Dam, Molecular Interaction Ecology, German Center for Integrative Biodiversity Research (iDiv), Leipzig 

Project background: 

Water availability is a key factor limiting both the productivity and sustainability of modern agriculture, and the concept of hydraulic niches has recently been proposed as an overlooked factor regulating the co-existence of plants in natural populations. Furthermore, drought and the associated stress signals in plants have been shown to interact with plants’ defense responses to herbivory, an interaction which is of significant concern for the protection of crops. Working with the wild tobacco Nicotiana attenuata, an ephemeral desert plant which exploits temporary water resources in the spring, we wish to study the water usage, photosynthetic rates and capacity, stress hormone levels, and biomass and seed production of populations containing both plants silenced in the expression of MITOGEN-ACTIVATED PROTEIN KINASE 4 (irMPK4), and empty vector controls (EV). irMPK4 plants have increased rates of transpiration and photosynthesis, reduced interaction with AMF, and reduced sensitivity to the drought stress hormone abscisic acid, in comparison to EV plants which behave like wild-type (WT) plants.

We hypothesize that the water usage, resilience to drought, and productivity of these genotypes in populations will depend on the frequency of each genotype, and the presence or absence of an active AMF inoculum. Specifically, we expect that some frequency between 0 % and 100% of irMPK4 plants will maximize the productivity of populations (in terms of biomass and seed production) per amount of water used, and that the addition of AMF will reduce water usage in these mixed populations.

To test these hypotheses, we will conduct bioassays with populations of irMPK4 and EV plants with and without active AMF inoculum; profile plant hormones and primary metabolites using liquid chromatography-mass spectrometry and spectrophotometric assays; measure photosynthetic rates and photosynthetic capacity using an infrared gas analyser and leaf chlorophyll fluorescence measurement system; measure plant biomass and seed production; perform soil analyses by measuring soil water potential, pH, humidity, AMF infection extent and nutrient content using previously researched soil analysis techniques; and record turgor pressure with YARA-ZIM probes.

The applicant for the proposed project should ideally have a background in applied ecological research, including bioassays with plants, and cultivating and conducting bioassays with arthropods, AMF, or endophytes. Furthermore, practical experience in more than one of the following techniques is desirable: measurement of photosynthesis and chlorophyll fluorescence; analytical chemistry techniques forquantification of primary and secondary plant metabolites (HPLC/UV-DAD, LC-MS, GC-MS); spectrophotometric assays to measure plant metabolites and enzyme activities; and molecular biological techniques (especially PCR and qPCR).

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