Drought Hardiness in Black Walnut
Walnut seed was collected from trees at eight locations along the 38th parallel from central Kansas to eastern Kentucky. Trees were grown in the greenhouse, nursery, and on upland and bottomland field sites in southern Illinois. In the greenhouse, after the trees were nearly fully grown, we stopped watering them and observed the number of days to wilting. Trees from the east generally wilted soonest. Chlorophyll Stability Index (CSI), a measure of chlorophyll breakdown caused by heating, was measured from samples collected in the nursery. There was no east-west trend for CSI differences. The early laboratory and greenhouse tests were weakly related or not related at all to field performance of 4-year-old trees on two field sites.
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Author(s): Calvin F. Bey
Publication: Tree Improvement and Genetics - Central States Forest Tree Improvement Conference - 1974