Abstract: The root hairs of trifoliate orange grafted with satsuma mandarin (Citrus unshiu Marc. cv. Okitsu Wase) at low soil moisture (-0.046 to -0.059 MPa) and high summer temperature (40-45°C) condition was studied under scanning electron microscope. The hair zone in actively growing roots positioned far apart from the root terminal and the hairs were mostly smaller with domft-shaped tips. Along with the severity of modification in roots under the present treatment hair zone positioned gradually nearer the root tip and the hairs gradually degraded. As a result the moderately modified roots possessed a few intact hairs but the extremely modified ones had only a few degenerated hairs or they were completely devoid of that. In that case, only the traces of abolished hairs were left with the root epidermis. At the initial stage of modification in roots, hairs elongated and this elongation was also found in the moderately modified roots but they had slightly irregular shapes. As the modification of root hairs progressed, their tips variously malformed having bending or swollen structure or they were severely injured. The malformed or injured root hairs subsequently destroyed completely.