Mycorrhiza Stimulates Root-Hair Growth and IAA Synthesis and Transport in Trifoliate Orange Under Drought Stress

The study investigated the effects of arbuscular mycorrhizal (AM) fungal inoculation on root-hair growth in trifoliate orange under drought stress. It was found that AM seedlings exhibited significantly greater root-hair density, length, and diameter, along with increased levels of root indoleacetic acid (IAA), compared to non-AM seedlings, regardless of soil moisture conditions. The mycorrhizal inoculation up-regulated genes involved in IAA biosynthesis and modulated the expression of auxin transporters, enhancing auxin influx and reducing efflux. These changes facilitated greater root-hair growth, which improved the plant's drought tolerance, demonstrating the beneficial role of mycorrhiza in auxin-mediated root development under stress conditions.