High Temperature Effects on Seedling Emergence and Embryo Protein Synthesis of Sorghum

High soil temperatures (>45°C) inhibit the field emergence of sorghum [Sorghum bicolor (L.) Moench] in the semiarid tropics. The objective of this study is to demonstrate that the measurement of embryo protein synthesis (EPS) is convenient an d rapid technique for the assessment of sorghum emergence at high soil temperatures. Two experiments were conducted, one using four landrace accessions and another using 14 commercially available lines. Seedling emergence was measured in a large water bath containing a series of soil-filled clay pots. The temperature of the soil in the pots could be regulated (35–50°C) using infrared lamps. Protein synthesis was measured by incubating embryo-containing half-seeds with 14C-labeled amino acids at different temperatures (35–40°C); the resulting labeled proteins were extracted for counting. The relative rankings of the landraces with respect to EPS and emergence demonstrated that the EPS technique clearly distinguished between lines that were able or unable to emerge at 50°C. However, with the commercially available lines, despite the agreement between the ranking of EPS and emergence, two lines diverged from this relationship, which is attributed to the greater complexity of the overall emergence process.