PhD Position (M/F) : Efficiency of light harvesting and photoprotection in native and invasive trees

Job Description

Thesis Subject

Invasive trees are a threat to forest sustainability in Hauts-de-France, including several species that have already been shown to be ecologically transformative (e.g., black cherry, black locust, box-elder) as well as those that are rapidly spreading from elsewhere in western Europe (e.g., northern red oak). As extreme weather increases the occurrence of stressful conditions, including drought and extreme heat, a key question facing forest managers is how new stressors will alter interactions between native and invasive trees. New evidence that forest invaders across the northern Hemisphere have greater light-use efficiency has prompted new research questions related to invader photosynthetic function and growth phenology.
During times of stress when more light is absorbed by leaves than can be used in photosynthesis, non-photosynthetic quenching (NPQ) processes in chloroplasts dissipate excess light energy as heat, which reduces photosynthetic light-use efficiency. An unexplored explanation for greater light-use efficiency in invasive trees is that, under the same environmental conditions, they are able to continue to photosynthesize at times when native species cannot, and thus less in need of photoprotective pigments that include anthocyanins, carotenoids, and other pigments.
Although NPQ quantification and pigment composition experiments have received substantial attention in agriculture from a production efficiency standpoint, NPQ dynamics have not been addressed in invasive species, nor has the xanthophyll cycle been studied extensively from the overall standpoint of shade tolerance. Importantly, some aspects of NPQ can be captured in real-time with spectral reflectance data. This opens up the possibility of continuous monitoring of plant growth-stress dynamics in native and invasive trees under realistic field conditions, via small reflectance sensors or drone-based remote sensing.
The specific objectives of the PhD project are twofold: 1) to experimentally compare photo-protective versus photo-productive dynamics of native and invasive species related to the xanthophyll cycle; and 2) identify best practices for remote sensing of photosynthetic light-use efficiency in the laboratory, with the aim of monitoring how natives and invaders react to stress in real-time under field conditions.

Your Work Environment

The project will be conducted at the EDYSAN lab (Ecologie et Dynamique des Systèmes Anthropisés, UMR 7058 CNRS-UPJV), Jules Verne University of Picardie – Amiens (France).
Experiments will take place in the Jules Verne University of Picardie plant phenomics facility, including the Plantscreen® platform equipped with automated fluorometric and hyperspectral imaging systems. The project will combine greenhouse experiments, controlled stress treatments, fluorometry, HPLC pigment analysis, and hyperspectral data analysis.
The candidate will work within an international and interdisciplinary research environment at the interface of ecophysiology, invasion ecology, and remote sensing.

Methodological Approach
The study will involve propagation of 30 species (15 native, 15 invasive) of ecologically similar native and invasive forest plants in the greenhouse for leaf function measurements in the plant phenomics facility.
Planned experiments include induction/relaxation curves of photosynthesis and photo-protection (NPQ) in response to fluctuating light conditions, and assays of leaf function and photo-protective chemistry (carotenoids via HPLC) in response to factorial stress treatments. Measurements will take advantage of automated hyperspectral measurements of whole plant canopies in the Plantscreen system, in addition to standard growth analysis.

Compensation and benefits

Compensation

2300 € gross monthly

Annual leave and RTT

44 jours

Remote Working practice and compensation

Pratique et indemnisation du TT

Transport

Prise en charge à 75% du coût et forfait mobilité durable jusqu’à 300€

About the offer

About the CNRS

The CNRS is a major player in fundamental research on a global scale. The CNRS is the only French organization active in all scientific fields. Its unique position as a multi-specialist allows it to bring together different disciplines to address the most important challenges of the contemporary world, in connection with the actors of change.

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