Distribution of Arbuscular Mycorrhizas in Peanut Root System.

Abstract

The distribution of arbuscular mycorrhizal colonies was assessed in a peanut (Arachis hypogaea L.) root system at early growth stage. Arbuscular mycorrhizal fungus (Gigaspora margarita Becker & Hall) was uniformly inoculated into non-sterilized soil. Peanut plants were grown in root boxes filled with the soil for 16 days inside a growth chamber. Approximately 66% of the total length of the mycorrhizal colonies was found on the 1st order latelral roots, while the rest was observed on the 2nd ones. In contrast, the tap root was scarcely colonized. On the 1st order lateral roots, regardless of the root length, it was evident that the frequency of the mycorrhizal colonies increased acropetally toward the root apex especially in the relatively aged roots that initiated on the proximal portion of tap root axis. In those lateral roots, the highest frequency of the mycorrhizal colony occurrence was recognized in the most apical part of the root, while many of relatively long colonies were found a little behind the root apex. However, the trend became unclear gradually in the relatively younger lateral roots initiated on the more distal potion of tap root axis. These facts clearly showed that in the 1st order lateral roots, the distribution and growth of mycorrhizal colonies are closely related with their initiating positions along tap root axis.