Numerous workers have noted that some plants shed mycorrhizal fungi when soil nutrients are supplemented, suggesting that under nutrient rich conditions, the costs to the plant of maintaining the symbiosis outweigh the benefits. In such systems the symbiosis is facultative. Much less is known about plant-mycorrhizal fungi interactions in woodland as opposed to grassland, prairie or agricultural systems. Of greater interest, we find that not all roots are equally colonized. Roots at young rhizome nodes contain few if any mycorrhizal fungi.
Fungal loads increase to their highest level at two to four year old nodes before dropping again.
P observed under the most heavily colonized nodes. Hypotheses relating to the regulation of plant-mycorrhizal fungal interactions will be discussed.