Effects of Frost and Freezing on Hydrocyanic Acid Potential of Sorghum Plants¹

Abstract

The effects of frost and freezing on hydrocyanic acid potential (HCN‐p) of plants of ‘Greenleaf’ and ‘Piper’ sudangrass and ‘Suhi‐1’, a sorghum ✕ sudangrass hybrid, were studied. The HCN‐p of plants of all plant heights and cultivars decreased during the autumn until frost occurred. Significant increases in HCN‐p were measured after most frosts. These increases were most evident from 1 to 6 days after frost. The response of HCN‐p to frost was greater in shorter than in taller plants. Plants of Suhi‐1 had a greater increase in HCN‐p than plants of Greenleaf or Piper. Freezes (−5 C or lower) resulted in death of the plants and caused a decrease in HCN‐p which continued until little or none was detected. This decrease in HCN‐p was observed for plants of all heights and cultivars.