Time-Course Changes in High Temperature Stress and Water Deficit During the First Three Days After Sowing in Hydro-Primed Seed: Germinative Behaviour in Sorghum

Abstract

Both drought and heat stresses substantially influence the germination pattern and subsequent establishment rates of sorghum. The timing of high temperature occuarrance, along with water deficit after seed sowing is investigated and methods for its alleviateion are evaluated. Two experiments were conducted on CSV 15 sorghum seeds after soaking treatments in 2, 4 or 6g NaCl l⁻¹ solutions. Several high temperature stress scenarios of 45◦C were administered at various times during the second day after sowing, or at a fixed time during the first, second or third days after sowing. Results revealed that the 18^th hour of the second day after sowing is more sensitive, in terms of the final germination percentage and germination index attained, than the 6^th, 12^th or 24^th hour. Seed treatment with 2g NaCl l⁻¹ was superior to untreated seeds in its response to high temperature stress, attaning more positive germinative characteristics. Heat shock on the first day after sowing had more negative impacts on germination than on the second or third days. It also caused an increase in radicle growth at the expense of plumule growth, thus decreasing the plumule:radicle ratio.