Finger Millet Response to Nitrogen Altering Root and Shoot Architecture.

The small grained cereal, finger millet (Eleusine coracana L. Gaertn), is valued by subsistence farmers in India and East Africa as a highly nutritious, low-input crop, able to adapt to a wide range of agronomic conditions. In contrast to high-input crops like maize, finger millet (FM) requires very little nitrogen (N) fertilization.  Exact mechanisms underlying the acclimation responses of FM to low N are largely unknown, both above and below ground. In particular, the responses of FM roots and root hairs to N or any other nutrient have not previously been reported. Given its low N requirement, FM also provides a rare opportunity to study responses to N starvation in a cereal. The objective of this study was to survey the shoot and root morphometric responses of FM to N starvation, including root hairs. Plants were grown with low N (5 kg/ha urea) or without N (N starvation) in a semi-hydroponic system on N-free clay in pails placed in the field. Plants were surveyed for root, shoot and seed head biomass and architectural traits. To our surprise, plants grown without added N grew to maturity, looked normal and produced grain. Plants responded to N starvation by decreasing shoot, root and seed head biomass. These declines under N starvation were associated with decreases in shoot tiller number, crown root number, total crown root length and total lateral root length, but with no consistent changes in root hair traits. Changes in tiller and crown root number appeared to coordinate the above and below ground acclimation responses to N. The remarkable ability of FM to grow to maturity without deliberately added N suggests that it is a potent N scavenger – perhaps able to use miniscule sources of environmental or biological N. The results suggest that FM should be further explored to understand this trait. Our observations are consistent with indigenous knowledge from subsistence farmers in Africa and Asia that this crop can survive extreme environments.