DEVELOPMENTAL CHANGES OF COTTON ROOT PRIMARY TISSUES INDUCED BY SALINITY

The effects of NaCl salinity on the development of primary tissues of cotton seedling roots (Gossypium hirsutum L. cv Acala SJ-2) were studied. Control and salinity treatments were imposed on 4-9-d-old plants grown in hydroponics in the light, with a photoperiod of 16 h. Observations were made on thin longitudinal and transverse sections from plastic embedded root samples taken at increasing distances from the root tip. Salinity induced a reduction of root growth rate and induced cells and tissues to initiate and complete maturation closer to the tip, except for the late metaxylem in the center of the stele. These responses were more pronounced with rising NaCl level in the growth medium. Roots exposed to salinity showed increased cellular vacuolation in all tissues but most strikingly in cortex and metaxylem cells. Other changes induced by salinity were the premature differentiation of protophloem sieve tube members, the dense staining of endodermal and some xylem parenchyma cells, the positional compres...