Characterizing moot responses to low phosphorus in pearl millet [Pennisetum glaucum (L.) R. Br.]

Adaptation to low water and soil P availability has been related to root properties. Two experiments were conducted in a greenhouse. Under hydroponics conditions, plants of the Sauna 3 cultivar were grown for 30 d with three levels of P (Pd = 0.0 mol L -1 P1 = OJ73 10 -3 mol L -1, and P2 = 1.65 10 -3 mol L -1). In the pot experiment, two oiltivars (Souna 3 and IBMV8402) were planted in pots filled with 19 kg of P-deficient and sandy soil and subjected to two watering regimes: well watered and water stressed at the vegetative phase from 23 d after sowing (DAS) to 30 DAS. Phosphores treatment consisted of two levels: application of phosphate fertilizer (P 2O 5) at the rate of 649 eg per pot (34 mg P 2O 5 kg -1 soil), referred to as F1, and no phosphate application, referred to as F0. The results showed that under P deficiency, pearl millet [Pennisetum glaucum (L.) R. Br.] presented an alteration of root parameters, particularly root volume, by the formation of root hair. Under non-water-limited conditions as well as in high or low P, IBMV8402 showed a better root and shoot growth. However, under drought conditions, the leaf water potential (Ψ f) of IBMV8402 (Ψ f = -5 MPa) decreased more than that of Sonna 3 (Ψ f = -3 MPa). In spite of this, P supply improved the root and shoot growth of IBMV8402. Finally, except for the condition of water stress and without P supply, P utilization efficiency exhibited by IBMV8402 was 20 to 50% higher than that of Souna 3 on the basis of shoot biomass production. © American Society of Agronomy.