Water Stressed Nodal Roots of Wheat: Effects on Leaf Growth

This experiment as undertaken to determine the efects of soil drying around the nodal and/or seminal root systems on the shoot growth of wheat (Triticum aestivum L.). Two split-root experiments were conducted, the first on newly emerged nodal roots of 18-day-old wheat plants, the second on 25-day-old plants. In both experiments, nodal and seminal roots were isolated from one another and water was withheld from either the nodal root chamber, the seminal root chamber, or both, over 6 days. In the first experiment, leaf growth was unaffected by withholding water from very short nodal roots, even though leaf relative water content of the droughted plants decreased. By comparison, both leaf elongation rate and relative water content decreased by withholding water from the seminal roots. On plants that were 1 week older, leaf growth rate and leaf relative water content decreased when nodal roots were drought-stressed. Leaf growth rate of seminal root droughted plants was more impaired than their nodal root counterparts, even though leaf relative water contents of the two treatments were the same. In both experiments, drought stress applied to the nodal root system enhanced nodal root growth more than seminal roots. These results suggest that seminal and nodal roots perceive and respond to drought stress differently with respect to the nature of the message conveyed to the shoots.