Temperature, Root Aeration, and Light Influence Slash Pine Nutrient Uptake Rates
In a controlled environment with 3 replications, plants absorbed water from well-aerated culture solutions about 70 percent faster at 22° than at 16°C and at 28° than at 22°C. They absorbed calcium, magnesium, and nitrate nitrogen 99, 88, and 67 percent faster, respectively, at 22° than at 16°C and 17, 13, and 22 percent faster at 28° than at 22°C. Phosphorus absorption averaged 70 percent and potassium absorption 115 percent higher at 22° than 16°C, but net uptake rate of neither ion was prominently influenced by further increasing temperature to 28°C. Lowering the oxygen level in solutions from near 90 to about 50 percent of equilibrium saturation with air eventually curtailed uptake of water, phosphorus, potassium, calcium, and magnesium but promoted uptake of nitrate nitrogen. Absorption rates of water, phosphorus, potassium, calcium, and magnesium were continuing to decline after 9 days of exposure to the low oxygen level, especially at the constant 28°C temperature. Diurnal changes in absorption rates varied with nutrient and with environment. Uptake rates were similar at 26,900 and 53,800 lux, measured at tips of the uppermost needles. Thus, relatively warm temperatures and good root aeration are required for continuous rapid absorption of ions by slash pine roots. Forest Sci. 21:401-410.
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