Chin J Plant Ecol ›› 2013, Vol. 37 ›› Issue (2): 93-103.DOI: 10.3724/SP.J.1258.2013.00010

• Research Articles •     Next Articles

Proliferation and growth of plant fine roots and the influences from nutrient variation― implications from the split-root experiments of Ailanthus altissima, Callistephus chinensis and Solidago canadensis

HU Feng-Qin, MOU Pu*()   

  1. College of Life Sciences, Beijing Normal University, Beijing 100875, China
  • Received:2012-10-30 Accepted:2012-12-22 Online:2013-10-30 Published:2013-01-31
  • Contact: MOU Pu


Aims Modular theory of plants considers plant roots are relatively independent in resource absorbing and responding to heterogeneous soil environments, particularly resource environments. According to the cost-benefit theory, proliferation, growth and death of individual absorbing roots (modules) depend upon their resource uptake related to the carbon costs of their construction and maintenance, with a certain time-lag. Thus we hypothesized that: 1) a root will die when available nutrients are below a certain low threshold and last for a certain period and 2) new roots will emerge when available nutrients are above a certain high threshold and last for a certain period.
Methods We designed a greenhouse split-root experiment using three plant species: Ailanthus altissima, Callistephus chinensis and Solidago canadensis. The plants were grown individually in pots, and then three fine roots (uptaking roots) per plant were carefully sorted and placed in three plastic vessels of about 70 mL with one root per vessel. Three nutrient levels of 0, 20 and 200 μg N·g-1soil were applied in the three vessels. These roots were carefully exposed and photographed every four days, and the numbers of lateral roots, the length of 1st order laterals and the root length were evaluated. Repeated-measure ANOVA was used for statistical analysis.
Important findings The numbers of laterals and total root length differed significantly among the three species and under the three N levels. Both lateral numbers and total root length were the least in the 0 μg N·g-1 treatment for A. altissima, and the highest in the 200 μg N·g-1 level for S. canadensis. The length of 1st order laterals was less responsive than the other two measures. No fine roots were found dead during the experiment. These results demonstrated that the different species had different growth rates of fine roots under the same N treatments as expected, and indicated that different species may have different N thresholds. Results provided partial support for our hypotheses and hints for future experiments. We suggest that a sufficient examination of the hypotheses may require 1) a longer experiment period, 2) control of other vital resources such as water and other limiting nutrients and 3) consideration of the resource contrast between the treatment patches and the overall level. The relative contrast of C costs between root construction and root maintenance should also be considered.

Key words: Ailanthus altissima, Callistephus chinensis, fine root initiation and death, nutrient patches, Solidago canadensis, split-root experiment