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  • Author or Editor: Oscar Monje x
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Two types of nondestructive chlorophyll meters were compared with a standard, destructive chlorophyll measurement technique. The nondestructive chlorophyll meters were 1) a custom built, single-wavelength meter, and 2) the recently introduced, dual-wavelength, chlorophyll meter from Minolta (model SPAD-502). Data from both meters were closely correlated with destructive measurements of chlorophyll (r2 = 0.90 and 0.93; respectively) for leaves with chlorophyll concentrations ranging from 100 to 600 mg·m-2, but both meters consistently overestimated chlorophyll outside this range. Although the dual-wavelength meter was slightly more accurate than the single-wavelength meter (higher r2), the light-scattering properties of leaf cells and the nonhomogeneous distribution of chlorophyll in leaves appear to limit the ability of all meters to estimate in vivo chlorophyll concentration.

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The effect of elevated root zone temperature (+0, +4, +6, +8, and +11 °C) on growth rates and carbon partitioning of ‘USU-Apogee’ spring wheat (Triticum aestivum L.) plants growing at constant air temperature (24 °C) in Turface was investigated. This experiment was performed to determine if wheat growth responded to elevated root zone temperature (RZT) and if so, to determine the temperatures for those responses. The RZT treatments were initiated 5 d after planting (DAP) to prevent RZT effects on germination from affecting results. The effects of increased RZT on development and carbon partitioning were determined from data collected during destructive harvests at 7, 15, 22, and 28 DAP. At a constant air temperature of 24 °C, reduced plant height was observed by 15 DAP at 30 °C RZT (+6 °C), and reduced leaf area was observed by 22 DAP at 28 °C RZT (+4 °C). Changes in leaf photosynthesis and stomatal conductance (g S) were not observed until 35 °C RZT (+11 °C), which was lethal by 22 DAP. Changes in carbon partitioning resulted in decreased leaf mass and increased stem and head mass fractions as well as accelerated development of reproductive structures. Although elevated RZT temperatures above air temperature affected physiological and morphologic parameters, they did not change plant phenology.

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