Creating a root architecture model: taprooted or adventitious-rooted Plantago lanceolata

Background/Question/Methods

Herbaceous plants can form root systems by either investing in one primary root, the taproot, or many thinner adventitious roots. Monocots always have adventitious root systems but eudicots can have either type depending on the species and even within a single species this can vary because of plant age, environment, or history of injury. Although these two root system architectures are clearly different, we know little about how these differences affect ecological functions and response. We used Plantago lanceolata, a species that can have either root architecture type, and tested performance within different plant communities. We conducted a series of trials to find the best methods to manipulate root system of Plantago lanceolata to produce plants with either of the two architectural types comparable physical health and condition. We then planted our taprooted and adventitious-rooted Plantago laceolata specimens in three local lawns along a productivity gradient with the lowest productivity site dominated by forbs and the other two more dominated by graminoids.

Results/Conclusions

We selected a procedure of root removal in seedlings 1-2 mm below the stem (hypocotyle) after the plants had produced rich green cotyledons (approximately 5 days old). This produced adventitious roots (growing from stem) and provided the easiest timeline for plant handling and health. Because of decreased biomass in treated plants, we began germinating adventitious-rooted plants a week earlier than plants with a taproot. In the field experiment, the two models did not differ between the acquisitive traits of specific leaf area or the specific root length and root tissue density of fine roots. Adventitious-rooted plants had greater investment in leaf and stem biomass, although this affect was removed when corrected for initial size. Stem and leaf investment differed among localities but aligned with community biomass; plants from more productive localities had lower leaf and stem biomass and this aligned with the productivity gradient. The use of a model species with either root system architecture may be valuable for understanding their role in different ecological contexts, for example along a moisture gradient.