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  • Author or Editor: R. A. Larson x
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Shepherdia rotundifolia Parry (roundleaf buffaloberry), a shrub endemic to the U.S. Colorado Plateau high desert, has aesthetic and drought tolerance qualities desirable for low-water urban landscapes. However, slow growth and too often fatal sensitivity to wet or disturbed soil stymies nursery production and urban landscape use. The goal of this study was to create an interspecific hybrid between the evergreen-xeric S. rotundifolia and its widely adapted, fast-growing, deciduous relative Shepherdia argentea (silver buffaloberry) distributed in western North America riparian habitats. Genetics and leaf morphology of the resulting S. argentea × S. rotundifolia hybrid are described and compared with the parents, as well as hybrid gas exchange as a reasonable proxy for growth rate and potential tolerance of poor soil. Hybrid genotypes were heterogenous, but contained an intermediate and equal contribution of alleles from genetically heterogenous parent populations. Leaf morphology traits were also intermediate between both parents. Aesthetic leaf qualities (silver-blue color and revolute margins) sought from S. rotundifolia were conserved in all offspring. However, gas exchange responses varied widely between the two surviving hybrids. Both hybrids showed greater tolerance of wet, fertile substrate—and promise for use in low-water landscapes—than S. rotundifolia. However, one hybrid conserved faster growth, and by inference possibly greater tolerance of wet or disturbed soil, from S. argentea, while the opposite was observed in the second hybrid. Following botanical nomenclature, we named this hybrid Shepherdia ×utahensis.

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Radiation measurements with different types of meters in several controlled environment facilities have been compiled to demonstrate the problems associated with insuring uniform radiation levels in separate faciities. Data are provided for a quantum meter, three photometers, a pyranometer and a far-red energy meter. Significant variations in total radiant energy in chambers under similar photosynthetically active radiation (PAR) levels were demonstrated. Measurement of light under cool white fluorescent and incandescent lighting with calibrated photometers from different manufacturers, varied by 20%. Greater variation occurred when photometer measurements were compared under different types of lamps. One of the most significant variations in different chambers was the intensity of incandescent radiation. This could only be effectively monitored and controlled with the far-red sensor. Factors are given for conversion between quantum, photometric and radiometric measurements, but high precision cannot be assumed in the use of these factors because of the differences in instrument sensitivity and variations in spectral output of lamps. The study documents the need for calibration of instruments under the same type of light source that is utilized in the growth chambers and for the use of more than one type of sensing instrument to quantify the radiation that controls plant growth.

Open Access