Root primordia

Sometimes adventitious roots gradually appear on tobacco plant stems. One can first observe the development of many isolated protrusions along the stem. They will later open, giving birth to a very short root, a primordium (figure 1). In some cases the roots can appear suddenly and the stem cortex breaks to "free" them. This phenomenon can occur at any level of the stem, yet it is more often observed on the lower to medium part of the stem.

It is not easy to give a rational explanation for this phenomenon. One may consider it as a "marker" of plant malfunction. In this situation, we highly recommend that you carefully observe the root system and stem to see if they are in good condition. It seems that plants can form aerial roots when their water and nutrient absorbtion is disturbed, for example as a result of root damage or cankers on the stem.

figure 1