Interaction of Gas Composition and Salinity upon Root Cell Division of Vicia faba L.1

Abstract

AbstractThe responses of Vicia faba L. seedlings to treatments consisting of combinations of O2, CO2, and N2 gases in the root environment were determined by microscopic examination of root tips at several times during and after treatment. Superimposed on the gaseous treatments were three nutrien solution salinity levels of 2.95, 5.95, and 8.95 mmho/cm. The plants were grown in an artificially lighted, controlled environment room with roots in airtight chambers. Roots in the chambers were sprayed intermittently (1 min/5 min) with one of the nutrient solutions.When roots were continually in air, the number of dividing cells in secondary root tips decreased linearly as the salinity level increased. The N2, treatment drastically reduced the number of dividing cells at all salinity levels; but during the recovery period, the numbers of dividing cells were 70, 80, and 100% of the controls at low, medium, and high salinity, respectively. Carbon dioxide levels of 3.5% and 6.0% with O2 at 17.5% and 15.0%, respectively, considerably reduced the number of dividing cells at a low salinity level and the number of dividing cells did not return to normal during recovery. At a medium salinity level 6.0% CO2 plus 15.0% O2 reduced the number of dividing cells, but 3.5% CO2 plus 17.5% O2 did not. During recovery following treatment with 6.0% CO2 plus 15% O2 at the medium salinity level, the number of dividing cells returned to that of the control. At the highest salinity level mitotic divisions in root tips were stimulated by CO2 treatments. These daa suggest that short periods of inundation or overirrigation may be less injurious to roots in saline than in nonsaline soil.