Jaz modular optical sensing suite

Shoot and root biomass were measured from the dry weight of leaves, stem and roots after oven-drying at 80 °C for 24 h. The measurement was performed in plants 40 days after germination. Leaf area was measured by digital image analysis using a scanner (Hewlett Packard Scanjet G2410, Palo Alto, California, USA), and the images were later processed using the ImageJ (NIH, Bethesda, Maryland, USA).
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The copyright holder for this preprint this version posted February 12, 2020. ; https://doi.org/10.1101/2020.02.11.943761 doi: bioRxiv preprint 6 Leaf spectral properties Spectral analysis of leaves was performed in the attached central leaflet of the fourth fully expanded leaf 56 days after germination. Leaf reflectance and transmittance were measured on the adaxial side of the leaflet throughout the 280-880 nm spectrum using a Jaz Modular Optical Sensing Suite portable spectrometer (Ocean Optics, Inc., Dunedin, Florida, USA).

The leaf optical properties were determined in the laboratory on vital, fresh, and fully developed D. caespitosa leaves. The reflectance spectra were measured from 290 to 880 nm, and the transmittance spectra from 290 to 800 nm, at a resolution of ~1.3 nm, using a portable spectrometer (Jaz Modular Optical Sensing Suite, Ocean Optics, Dunedin, FL, USA; grating, #2; slit size, 25 µm) with an optical fibre (QP600-1-SR-BX, Ocean Optics) and an integrating sphere (ISP-30-6-R; Ocean Optics). The leaf reflectance spectra were measured for the adaxial leaf surface by irradiation with a UV/VIS-near infrared (NIR) radiation source (DH-2000, Ocean Optics) . The spectrometer was calibrated to 100 % reflectance using a white reference panel with > 99 % diffuse reflectance (Spectralon, Labsphere, North Sutton, NH, USA). The spectrometer was calibrated to 100 % transmittance with a light beam that passed directly into the interior of the integrating sphere.

The optical properties of bark and leaves (when these were present) were determined in the laboratory on the day of sampling. Bark was carefully removed from the twigs with a razor blade. The measurements were performed in the range from 290 nm to 800 nm for reflectance and in the range from 290 nm to 800 nm for transmittance, using a portable spectrometer (Jaz Modular Optical Sensing Suite; Ocean Optics Inc., Dunedin, FL, USA; grating, #2; slit size, 25 µm) that was connected with an optical fibre (QP600-1-SR-BX; Ocean Optics Inc.) and an integrating sphere (ISP-30-6-R; Ocean Optics Inc.). The resolution of the measurements was ~1.3 nm. The reflectance spectrum was measured for the bark/leaf surface by illumination with a UV/VIS-near-infrared (NIR) light source (DH-2000; Ocean Optics, Inc.) . We calibrated the spectrometer to 100% reflectance using a white reference panel with > 99% diffuse reflectance (Spectralon; Labsphere, North Sutton, NH, USA). In the case of the transmittance spectra, periderm surface was illuminated with a light source, while the integrating sphere that captured the transmitted light was positioned below the bark (or leaf). The incident angle of bark/leaf illumination was 90°. Prior to the measurement, we calibrated the spectrometer to 100% transmittance by light beam passing directly into the interior of the integrating sphere.