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ARS Home » Pacific West Area » Davis, California » Crops Pathology and Genetics Research » Research » Research Project #438412

Research Project: Developing Solar-induced Chlorophyll Fluorescence as a Ground-based and Remotely-sensed Physiological Indicator of Grapevine Stress

Location: Crops Pathology and Genetics Research

Project Number: 2032-21220-008-030-T
Project Type: Trust Fund Cooperative Agreement

Start Date: Apr 15, 2020
End Date: Apr 15, 2021

1) In controlled conditions, compare active (traditional fluorescence sensors) and passive (Solar-Induced Chlorophyll Fluorescence (SIF) fluorescence measurements at the leaf scale to validate signal output for new ground-based (tower) and remotely sensed (satellite) approaches for grapevines and vineyards. a. Compare responses of common grapevine varietals for drought, heat, and nutrient stressors. b. Combine results with current modelling efforts aimed at understanding how stress-induced changes in leaf structure impact signals gleaned from various sensor platforms. 2) Utilize existing experimental infrastructure (e.g. GRAPEX and other flux systems) to test SIF based physiological indicators from other methods.

Leaf-level performance will be scaled up to canopy-level productivity and linked via ChlF measurements described below. Experiments will be conducted under both controlled (potted plants subjected to drydown) and field conditions. Utilizing our standard leaf gas exchange, ChlF and water potential measurements on potted vines subjected to well-watered soil drydown conditions, while simultaneously capturing fluorescence and transmittance profiles in Vitis vinifera varieties (Cabernet Sauvignon and Chardonnay initially). Leaves from these experiments will be measured and then immediately scanned with microCT. SIF will be retrieved from both top and bottom of leaves to relate to light absorption profiles. It is currently not known why SIF spectra change on each side of a leaf or how sun vs shade leaves within a canopy produce varied signals. Transmittance electron microscopy (TEM) will be used to observe other anatomical changes that impact light absorption and fluorescence profiles (i.e. chloroplast positioning, cell wall area, cell wall thickness, tortuosity, pathlengths, etc.). In order to get a comprehensive understanding of ChlF responses to environmental variables (i.e. soil water content, heat, light) at the field scale, we will use state of the art equipment to monitor ChlF from passive and active techniques at the leaf and canopy level. Complementary PAM and spectrally resolved leaf fluorescence will be measured an instrument that builds on a portable GFS-3000 gas exchange and fluorescence system, which was modified adding a QE Pro high sensitivity spectrometer. These measurements will allow to directly connect ChlF responses from active and passive methods. Continuous canopy SIF (data record every 20 seconds throughout the growing season) will be measured using a novel ground-based spectrometer -PhotoSpec. This equipment measures SIF in the red (670–732 nm) and far-red (729–784 nm) wavelength range as well as canopy reflectance (400–900 nm) to calculate vegetation indices, such as the normalized difference vegetation index (NDVI), the enhanced vegetation index (EVI), and the photochemical reflectance index (PRI). PhotoSpec includes a 2D scanning telescope unit which can be pointed to any location in a canopy with a narrow field of view, allowing for automated observations across different points over an area of a radius of up to 100 m. Continuous leaf PAM Fluorescence will be measured using a weatherproof Walz MONI-PAM fluorometer. This equipment can measure long-term fluorescence PSII parameters in the field, and thus provided a unique opportunity to compare measurements from PhotoSpec. Four independent fluorometer emitter-detector units with PPFD sensors (MONI-head/485) will be deployed for the experiments. Equipment will be deployed on experiments conducted as part of the Grape Remote sensing Atmospheric Profile & Evapotranspiration eXperiment (GRAPEX). Consequently, these observations will be run alongside canopy CO2, water vapor, energy, and momentum exchange from eddy covariance systems.