The responses of lateral roots and root hairs to nitrogen stress in cotton based on daily root measurements

Abstract Lateral roots and root hairs are essential portions of cotton roots. However, the morphology and lifespan of cotton ( Gossypium hirsutum L.) lateral roots and root hairs in response to nitrogen stress have remained unknown. Two cotton cultivars were assessed when no nitrogen and normal nitrogen (138 mg N·kg −1 soil) were added. The daily acquisitions of root phenotype information including the lateral root angle, lateral root density, lateral root diameter, lateral root lifespan, root hair length, root hair density, and root hair lifespan, were obtained in situ by a self‐designed platform of RhizoPots equipped with high‐resolution scanners. Nitrogen starvation significantly reduced the growth of shoots and roots, although there was less reduction of roots than shoots. Root hairs were the first organ to respond to nitrogen deficiency through morphological changes. The lateral root diameter and angle as well as the root hair lifespan decreased significantly under nitrogen stress. However, nitrogen deficiency dramatically increased the lateral root lifespan, root hair density and length. Our results demonstrate that low nitrogen can induce notable changes in lateral roots and root hairs, which may play a crucial role in the adjustment to nitrogen uptake, particularly in species that can adapt to low nitrogen availability.