Tomato root growth and phosphorus absorption kinetics by tomato plants as affected by phosphorus concentration in nutrient solution

Abstract

To evaluate the effects of P concentrations in nutrient solution on root growth and on root physiological characteristics involved in P uptake by tomato Lycopersicon esculentum Mill plants, six seedlings were grown in nutrient solution at initial concentrations of 48.5, 97, 194 and 388 µM P until one day before harvest. They were then transferred to solutions with P at 20 µM and 30 µM, and the depletion curves and Michaelis-Menten parameters were determined. Increases in the initial P concentration increased plant dry weight and shoot: root dry weight ratio. I_max values decreased with the increase in the concentration of P in the treatment solution; however, these were not significantly affected by P concentration in the depletion solution. Variation in K_M values were not statistically significant. The relative net P influx increased with decreased P concentrations in the nutrient solution, mainly due to increase I_max values. The conclusions were that as P supply increased and as the plant P contents are sufficient for maximum growth, the rate of P uptake tends to be lower. The results also indicate that total P uptake by tomato seedlings depends on the amount of root surface area exposed to P.