COS 15-9
Threshold nutrient levels for the birth and die of rootlets

Monday, August 11, 2014: 4:20 PM
314, Sacramento Convention Center
Yan Yang, College of Life Sciences, Beijing Normal University, Beijing, China
Paul P. Mou, College of Life Sciences, Beijing Normal University, Beijing, China

Plant roots are modular that respond to soil variability relatively independently. Recent studies indicated critical roles of whole plant control on root plasticity. We demonstrated earlier that growth and death of rootlets highly correlated to the N contrast between patch and background of soil. However, we tested only single rootlets in patches under different patch/background N contrasts. What would root growth/death be affected by groups of roots in different N patches? We conducted a greenhouse experiment by growing Ailanthus altissima, and Solidago canadensis in pots that were equally divided into two compartments. Two N treatment contrasts were established: 2 and 10 μg N/g soil, or 2 and 100 μg N/g soil in the low and high N compartments, respectively. The compartments were fertilized every 7 days. The root proportions between the high and low compartments were set as 1:7, 1:3, 1:1, 3:1 and 7:1. Selected rootlets were positioned against compartment windows for monitoring root growth every 4 days. After 28 days, the plants were harvested, and selected rootlets from the two compartments of each plant were scanned by WinRhizo Tron. The root mass, aboveground mass of each plant were determined and statistically analyzed.


Although no roots were found dead in the low N compartments for both species, fine root mass changes in the two species in different initial root proportions showed the similar pattern in both high (100 vs. 2 μg N/g) and low (10 vs. 2 μg N/g) N contrasts. In general, proportions of root mass in low compartments increased when the initial proportions were low, but decreased as the initial proportions were high. The balance root distribution (i.e. final proportion of 50:50) in both contrasts was resulted from the initial proportions between 1:3 and 1:1. The root elongation and proliferation tended to increase in high N compartments. In addition, fine root allocation changes among different initial proportions between high and low N compartments indicated the trend found in our previous studies though the extremities were much reduced.