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Hydrocyanic Acid Potentials in Leaf Blade Tissue of Eleven Grain Sorghum Hybrids
Author(s) -
Eck Harold V.
Publication year - 1976
Publication title -
agronomy journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.752
H-Index - 131
eISSN - 1435-0645
pISSN - 0002-1962
DOI - 10.2134/agronj1976.00021962006800020036x
Subject(s) - sorghum , sowing , hybrid , forage , agronomy , leaf blade , human fertilization , cultivar , biology , chemistry , horticulture
Hydrocyanic acid potentials (HCN‐p) of grain sorghums [ Sorghum bicolor (L.) Moench] need not be considered in grain production but become important when fresh forage is fed to livestock. This study involved determination of seasonal leaf blade HCN‐p levels of 11 field‐grown grain sorghum hybrids, relationships between HCN‐p levels in growth chamber‐grown seedlings and older fieldgrown plants, and effects of N fertilization on seasonal leaf blade HCN‐p levels. Growth chamber plants were grown in vermiculite, subirrigated daily with nutrient solution. Plants were harvested and assayed for HCN‐p 10, 14, and 18 days after planting. In 1972, the 11 hybrids were field‐grown on N fertilized soil. In 1973, ‘DeKalb E‐59’ was grown on N fertilized and on N‐deficient soil. Field‐grown hybrids were assayed for HCN‐p weekly from 27 (1972) or 37 (1973) days after planting until physiological maturity. HCN‐p was determined potentiometrically on homogenized, β ‐glucosidase hydrolized leaf blade tissue. Relationships between HCN‐p levels at sampling dates during the season and seasonal average HCN‐p levels indicated that, for purposes of ranking cultivars, approximately equal precision would be attained at any time from growing point differentiation through soft dough. The correlation between HCN‐p levels in 18‐day‐old growth‐chamber plants and seasonal average HCN‐p levels of field plants was significant at the 10% level (r = 0.56) but HCN‐p levels in 10‐ and 14‐day‐old plants were not significantly related to seasonal average HCN‐p levels of field plants. HCN‐p in leaf blade tissue was highly dependent on N availability. At a sustained adequate level of N, HCN‐p levels in sorghum leaf blade tissue declined from the seedling stage to about flag leaf and then remained fairly constant until they declined at the approach of maturity. HCN‐p levels exceeded the “threshold of danger” (200 ppm) until physiological maturity. On N‐deficient soil, leaf blade HCN‐p levels declined to a low level (<100 pm) at soft dough.