Local adjustment of exodermis to nutrient deficiency in crop species

Translating insights from Arabidopsis to crops to support the breeding programs remains a major challenge in plant science, particularly for root traits controlling nutrient transport. Here, we investigated how nutrient deficiency affects the differentiation of exodermis, a protective apoplastic barrier of the outer root cortex, in multiple crops.

Panel of exodermis-forming monocot and dicot species was examined, including the transformable barley cultivar Hordeum vulgare cv. Golden Promise and the model monocot Brachypodium distachyon. Plants were exposed to nutrient deficiencies under homogeneous and split-root hydroponic conditions.

Among the tested nutrients, nitrogen deficiency emerged as the most potent stimulus of exodermal differentiation, while phosphorus deficiency elicited similar but weaker responses. In split-root systems, most species showed localized enhancement of exodermal differentiation in roots directly exposed to N deficiency, including lateral roots. In Zea mays, localized N deprivation was associated with locally altered root apoplastic permeability, minor retranslocation of nutrients toward deficient roots, and hormonal changes (especially of abscisic acid. Exogenous ABA promoted exodermal differentiation in Z. mays.

Despite interspecific differences in exodermal differentiation, the selected species exhibited a largely conserved exodermal response to N deficiency, indicating the existence of a conserved mechanism regulating root transport properties under nutrient-limiting conditions.