Comparison of Campbell-leaf press with standard plant water stress measurements for four species

The Campbell-Brewster (J-14) leaf press is a compact alternative to the pressure chamber for plant water potential determination. Data comparing the J-14 with the pressure chamber (?x) or with canopy temperatures (Tc) and crop water stress index (CWSI) are limited. All three J-14 end points (exudation from cut or uncut leaf edges or darkening of interveinal areas) were highly correlated among themselves for the four species studied. Correlations of J-14 end points with other stress indicators from unstable diurnal periods were poor. Our data shoved a species-related reliability of the J-14. The J-14 produced r2 values above 0.7 for soybean for all but comparisons with CWSI or Tc minus air temperature (?T), and for corn for ?x only. The J-14 did not perform well for tomato or rapeseed. Failure of J-14 or ?x, to correlate well with CWSI suggests difficulty with CWSI measurement under humid southeastern conditions

A comparison of pressure chamber, leaf-press, and canopy temperature for four species under humid conditions

Numerous techniques are currently available for measurement of plant water status in field environments, including pressure chambers and indices based upon infrared-determined canopy temperatures. The Campbell-Brewster (J-14) leaf press has been promoted as a compact alternative to the pressure chamber for plant water potential determination. In-depth comparisons of the J-14 (?J) with the pressure chamber (?x) or with canopy temperatures (Tc) and crop water stress index (CWSI) have been limited, and an evaluation of the technique in a humid environment was needed. All three J-14 end points [exudation from cut (?Jc) or uncut leaf edges (?Ju) or darkening of interveinal areas (?Jd)] were highly correlated among themselves for the four species studied. Correlations of J-14 end points with other stress indicators from unstable diurnal periods were poor. None of the water status indicators correlated well with leaf diffusive resistance. Our data showed a species-related reliability of the J-14. The J-14 produced r2 values above 0.7 for soybean [Glycine max. (L.) Merr.] for all but comparisons with CWSI or Tc, minus air temperature (?T), and for corn (Zea mays L.) for ?x only. The J-14 did not perform well for tomato (Lypersician esculentum Mill.) or rapeseed (Brassica napes L.), and is probably best regarded only as a relative indication of plant water status in the absence of calibration with other techniques. Failure of ?x or J-14 to correlate well with CWSI underscores difficulty with CWSI measurement under humid conditions

Bulk ion heating with ICRH in JET DT plasmas

Reactor relevant ICRH scenarios have been assessed during DT experiments on the JET tokamak using H mode divertor discharges with ITER-like shapes and safety factors. Deuterium minority heating in tritium plasmas was demonstrated for the first time. For 9% deuterium, an ICRH power of 6 MW gave 1.66 MW of fusion power from reactions between suprathermal deuterons and thermal tritons. The Q value of the steady state discharge reached 0.22 for the length of the RF flat-top (2.7 s), corresponding to three plasma energy replacement times. The Doppler broadened neutron spectrum showed a deuteron energy of 125 keV, which was optimum for fusion and close to the critical energy. Thus, strong bulk ion heating was obtained at the same time as high fusion efficiency. Deuterium fractions around 20% produced the strongest ion heating together with a strong reduction of the suprathermal deuteron tail. The ELMs had low amplitude and high frequency and each ELM transported less plasma energy content than the 1% required by ITER. The energy confinement time, on the ITERH97-P scale, was 0.90, which is sufficient for ignition in ITER. 3He minority heating, in approximately 50:50 D:T plasmas with up to 10% 3He, also demonstrated strong bulk ion heating. Central ion temperatures up to 13 keV were achieved, together with central electron temperatures up to 12 keV. The normalized H mode confinement time was 0.95. Second harmonic tritium heating produced energetic tritons above the critical energy. This scheme heats the electrons in JET, unlike in ITER where the lower power density will allow mainly ion heating. The inverted scenario of tritium minority ICRH in a deuterium plasma was demonstrated as a successful heating method producing both suprathermal neutrons and bulk ion heating. Theoretical calculations of the DT reactivity mostly give excellent agreement with the measured reaction rates

Comparison of Campbell-leaf press with standard plant water stress measurements for four species

The Campbell-Brewster (J-14) leaf press is a compact alternative to the pressure chamber for plant water potential determination. Data comparing the J-14 with the pressure chamber (?x) or with canopy temperatures (Tc) and crop water stress index (CWSI) are limited. All three J-14 end points (exudation from cut or uncut leaf edges or darkening of interveinal areas) were highly correlated among themselves for the four species studied. Correlations of J-14 end points with other stress indicators from unstable diurnal periods were poor. Our data shoved a species-related reliability of the J-14. The J-14 produced r2 values above 0.7 for soybean for all but comparisons with CWSI or Tc minus air temperature (?T), and for corn for ?x only. The J-14 did not perform well for tomato or rapeseed. Failure of J-14 or ?x, to correlate well with CWSI suggests difficulty with CWSI measurement under humid southeastern conditions

A comparison of pressure chamber, leaf-press, and canopy temperature for four species under humid conditions

Numerous techniques are currently available for measurement of plant water status in field environments, including pressure chambers and indices based upon infrared-determined canopy temperatures. The Campbell-Brewster (J-14) leaf press has been promoted as a compact alternative to the pressure chamber for plant water potential determination. In-depth comparisons of the J-14 (?J) with the pressure chamber (?x) or with canopy temperatures (Tc) and crop water stress index (CWSI) have been limited, and an evaluation of the technique in a humid environment was needed. All three J-14 end points [exudation from cut (?Jc) or uncut leaf edges (?Ju) or darkening of interveinal areas (?Jd)] were highly correlated among themselves for the four species studied. Correlations of J-14 end points with other stress indicators from unstable diurnal periods were poor. None of the water status indicators correlated well with leaf diffusive resistance. Our data showed a species-related reliability of the J-14. The J-14 produced r2 values above 0.7 for soybean [Glycine max. (L.) Merr.] for all but comparisons with CWSI or Tc, minus air temperature (?T), and for corn (Zea mays L.) for ?x only. The J-14 did not perform well for tomato (Lypersician esculentum Mill.) or rapeseed (Brassica napes L.), and is probably best regarded only as a relative indication of plant water status in the absence of calibration with other techniques. Failure of ?x or J-14 to correlate well with CWSI underscores difficulty with CWSI measurement under humid conditions