Wholly expanded top most leaves of plants were analyzed under infrared gas analyzer (IRGA, Model LI6400XT, LI-COR Lincoln, Nebraska, USA) to determined Gas exchange parameters. The experiment was carried out between 11.00 and 12.00 h at light-saturating intensity, 2 cm2 of leaf area, block temperature (25 °C), CO2 flow controller (300 µmol s−1) and PAR (1600 μmol photons m−2 s −1). Before proceeding the experiment calibration of IRGA was done that includes zeroing replacement of drierite and soda lime. The healthy third leaf from apex was taken into account for recording leaf gaseous exchange attributes like transpiration rates (E) (mmol H2O m−2 s−1), stomatal conductance (gs) (mmol H2O m−2 s−1), photosynthetic rate (PN) (µmol CO2 m−2 s−1) and water use efficiency (WUE). (Relationship between photosynthesis and transpiration).
Model li 6400xt
Manufactured by LI COR
Sourced in United States
The LI-6400XT is a portable photosynthesis system designed for measuring gas exchange in plants. It is a self-contained unit that can be used to measure photosynthesis, respiration, and transpiration rates in a variety of plant species under different environmental conditions.
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Lab products found in correlation
7 protocols using model li 6400xt
1
Leaf Gas Exchange Parameters Analysis
2
Photosynthetic Response to Light Intensity
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All genotypes were grown in pots together in the same controlled-environment chambers under LL (250 μmol m–2 s–1) for 5 weeks. Thereafter, half of the plants were transferred to HL (800 μmol m–2 s–1) for 8 h, while the remaining half were maintained for 8 h at 250 μmol m–2 s–1. Photosynthetic gas exchange measurements were performed on plants in the controlled-environment chambers between 7 h and 8 h into the photoperiod under each irradiance.
Measurements were performed on fully expanded leaves essentially as described by Soares et al. (2008) using a LICOR portable photosynthetic gas exchange system (Model LI-6400XT).
Photosynthetic CO2 assimilation rates were measured on whole leaves at 420 ppm CO2, 20 °C, at an irradiance of 400 µmol m–2 s–1. Leaves were allowed to reach steady-state gas exchange conditions by maintaining the leaves for 10 min in the light and CO2 conditions of the chamber prior to measurements. All experiments were conducted at 60% relative humidity. Vapour water deficits were kept constant throughout the assays.
Measurements were performed on fully expanded leaves essentially as described by Soares et al. (2008) using a LICOR portable photosynthetic gas exchange system (Model LI-6400XT).
Photosynthetic CO2 assimilation rates were measured on whole leaves at 420 ppm CO2, 20 °C, at an irradiance of 400 µmol m–2 s–1. Leaves were allowed to reach steady-state gas exchange conditions by maintaining the leaves for 10 min in the light and CO2 conditions of the chamber prior to measurements. All experiments were conducted at 60% relative humidity. Vapour water deficits were kept constant throughout the assays.
3
Automated Microclimatic Measurements in Experiments
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Climatic variables including solar radiation (Rn, W m−2), air relative humidity (RH, %), temperature (T, °C), precipitation (P, mm) and wind velocity (Wv, m s−1) were continuously measured in each treatment in B1 by a HOBO weather station (Onset Computer, Bourne MA, USA). The sensors were placed at canopy level (approximately 2.5 m). VPD is calculated based on Goff–Gratch equation [48 ]. Microclimate variables including leaf temperature, leaf VPD and incoming photosynthetically active radiation (PAR, µmol (photons) m−2 s−1), at a height of approximately 1.5–1.7 m, across the three blocks (9 plots) at mid-day on a weekly basis during the growing season, were recorded by the instantaneous photosynthesis measurement system (Model LI-6400XT, Licor, Lincoln, NE, USA). Soil volumetric water content (VWC) at two depths (20 and 40 cm) in three randomly selected locations per plot in B1 was measured by EC-5 sensors (Decagon, Pullman, WA, USA) at 20-minute intervals. Soil VWC at the 20 cm depth was also manually measured weekly in the three blocks using a GS-1 portable measuring system (Decagon, Pullman, WA, USA).
4
Stomatal Conductance Measurement in xopC2 Transgenic Seedlings
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Three-week-old xopC2 IE transgenic seedlings were pretreated with 30 μM DEX or mock at 24 h before spray inoculation of Xoc strains. At 2 dpi, stomatal conductance was measured using a photosynthesis system (Model LI-6400XT, Li-Cor Inc., Lincoln, NE, USA)62 (link). Briefly, stomatal conductance was measured with a 2 × 3 cm leaf chamber supplied with a red-blue LED light source, and parameters were set as 400 μmol mol−1 CO2 and 200 μmol m−2 s−1 photosynthetic photon flux density (PPFD).
5
Chlorophyll Fluorescence Analysis of Leaves
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Chl a fluorescence quenching measurement were performed on intact leaves using the LICOR portable photosynthetic gas exchange system (Model LI-6400XT) equipped with the leaf chamber fluorometer between 7 h and 8 h into the photoperiod under each irradiance. Plants were dark adapted for 45 min before each procedure (Plumb et al., 2018 (link)). Fm and Fo, the maximum and minimum yields of fluorescence, respectively, were measured in dark-adapted leaves. Dark-adapted Fv/Fm, Φ PSII, and non-photochemical quenching (NPQ) were calculated as Fv/Fm=(Fm−Fo)/Fm, Φ PSII=(Fm′−Fs)/Fm′, and NPQ=(Fm−Fm′)/Fm′, respectively.
6
Grapevine Gas Exchange Measurements
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The grapevine gas exchange was assessed only in third growing season, using a portable infrared gas analyzer -IRGA (Model LI-6400XT, Li-Cor, Lincoln, NE, USA) described in A. R. M. Chaves et al., (2016) . Measurements of net photosynthesis (A), transpiration (E) and stomatal conductance (g s ) were initiated before the interruption of irrigation in RDI and DI treatments, and were ended close to harvesting. Evaluations were carried out after 51, 79 and 107 dap. Measurements were performed at four different times throughout the day (07h00, 10h00, 13h00 and 15h00), always the same adult and healthy leaves which showed good and uniform characteristics as color, age and size.
7
Photosynthetic Parameters Measured with IRGA
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The photosynthetic parameters were determined using the IRGA-Infrared Gas Analyzer, model Li-6400 XT from Licor (Made in Lincoln, Nebraska -United States of America [42] . Forty readings per treatment in the same plant for each block were performed on the mature leaves most exposed to the sun, with no senescence sign for having higher photosynthetic rate. In both years, the readings were performed in the second half of October (full bloom period), in periods with higher photosynthetic rates (from 11h to 13h). The chamber's internal flow was fixed at 400 µmol s -1 and the internal photosynthetically active radiation (PAR) at 1500 µmol s -1 m -2 , as recommended by the manufacturer for C3 plants [38] (link). Through the evaluations were obtained the data of liquid assimilation of CO 2 or photosynthetic yield (A, µmol CO 2 m -2 s -1 ), the intercellular concentration of CO 2 (Ci, µmol mol -1 air), stomatal conductance (Gs, mol CO 2 m -2 s -1 ) and transpiration rate (E, mol CO 2 m -2 s -1 ). Through the relation between the CO 2 assimilation and transpiration rate (A/E), the water-use efficiency (WUE, mmol H 2 O -1 ) was calculated, while the carboxylation efficiency (A/Ci) was due to the CO 2 assimilation and intercellular CO 2 concentration ratio in the leaf [43, 44] .
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