Influence of Osmotic Potential, Temperature, and Calcium on Growth of Plant Roots1

Studies to determine influences of temperature, osmotic potential, and Ca on root growth were conducted. Hourly elongation of pea roots at 27C was a maximum of about 1.0 mm/hr after 64 to 72 hours. Osmotic potentials of −7.8 and −13.1 bars reduced root growth of peas by about 50 and 85%, respectively. Maximum hourly elongation of cotton was about 3.3 mm/hr at 32 to 38 C after 24 to 48 hours. At optimum temperature conditions and salinity levels of −0.8, −6.6, and −12.9 bars, maximum root elongation of cotton averaged 3.3, 1.8, and 0.8 mm/ hr, respectively. Optimum temperature for root elongation of cotton varied from 27 to 38 C depending upon the salinity and Ca levels. At low salinity levels Ca requirement for maximum elongation was low, but at moderate and high salinity levels Ca requirement for maximum elongation was 15 to 20 meq/liter. The stimulatory effect of Ca on root growth of cotton under salinity conditions was greatest at high temperatures (32 to 38 C). However, root growth and vigor was significantly improved by Ca at low temperatures (21 C). Calcium seems to induce root vigor and growth at adverse soil temperatures and salinity conditions. Additions of Ca may promote better stands and higher yields on certain soils.