Lateral root branching is a genetically defined and environmentally regulated process. Auxin is required for lateral root formation, and mutants that are altered in auxin synthesis, transport or signaling often have lateral root defects. Crosstalk between auxin and ethylene in root elongation has been demonstrated, but interactions between these hormones in the regulation of Arabidopsis lateral...

INSIGHT In 1880, Charles Darwin noted that " some influence, " later shown to be in-dole-3-acetic acid (IAA), moves from the tip of an oat coleoptile to the region below the tip, where it controls elongation (Darwin, 1880). Darwin's statement was probably the first description of polar auxin transport, a phenomenon that has received considerable attention in the ensuing decades for two main rea...

A stunted root system is a significant symptom of iron (Fe) toxicity, yet little is known about the effects of excess Fe on lateral root (LR) development. In this work, we show that excess Fe has different effects on LR development in different portions of the Arabidopsis (Arabidopsis thaliana) root system and that inhibitory effects on the LR initiation are only seen in roots newly formed duri...

Under unfavorable environmental conditions, the stress phytohormone ABA inhibits the developmental transition from an embryo in a dry seed into a young seedling. We developed a genetic screen to isolate Arabidopsis thaliana mutants whose early seedling development is resistant to ABA. Here, we report the identification of a recessive mutation in AUXIN RESISTANT1 (AUX1), encoding a cellular auxi...

A balanced supply of essential nutrients is an important factor influencing root architecture in many plants, yet data related to the interactive effects of two nutrients on root growth are limited. Here, we investigated the interactive effect between phosphorus (P) and magnesium (Mg) on root growth of Arabidopsis grown in pH-buffered agar medium at different P and Mg levels. The results showed...

The inhibitory effect of ammonium on primary root growth has been well documented; however the underlying physiological and molecular mechanisms are still controversial. To avoid ammonium toxicity to shoot growth, we used a vertical two-layer split plate system, in which the upper layer contained nitrate and the lower layer contained ammonium. In this way, nitrogen status was maintained and onl...

Auxins are key regulators of plant development. Plants employ a specialized delivery system termed polar auxin transport to convey indole-3-acetic acid from source to target tissues. Auxin transport is mediated by the combined activities of specialized influx and efflux carriers. Mutational approaches in the model plant, Arabidopsis thaliana, have led to the molecular genetic characterization o...