Phosphate absorption by air-stressed root systems

Abstract

Root systems from plants grown in nutrient solution were exposed to air and either transferred to fresh nutrient solution containing (32)P-labeled phosphate or placed in a psychrometer to determine their water potential. The amount of (32)P absorbed by maize and soybean roots in the hour following their exposure to air was proportional to their water potential at the time they were transferred. Some cells, probably located in the stele, were more resistant to moisture stress than others. Absorption of (32)P by all cells was severely inhibited by water potentials below-12 to-15 bars. Nearly normal amounts of the radioisotope and total phosphate were absorbed within 72 hr following root exposure of 4 of 5 species of detopped plants; some phosphorus was lost to the nutrient solution. Uptake of (32)P by passive processes was increased slightly by exposure of roots of intact maize plants to air, but the increase did not compensate for the substantial reduction in actively-absorbed (32)P.

Phosphorus Uptake from Soil by Lolium perenne During and After Severe Drought

“…Clarkson, Sanderson & Scott Russell (1968) and Dove (1969) found that on rewetting droughted roots, uptake and transport of phosphorus was much reduced, as in the present study. Clarkson, Sanderson & Scott Russell (1968) and Dove (1969) found that on rewetting droughted roots, uptake and transport of phosphorus was much reduced, as in the present study.…”

Effect of light and water stress on mineral element composition of plants1

“…When (20). Passive uptake of H~PO7 was increased by exposure to air, but the increase did not compensate for reduction in the active HjPOT absorption.…”

“…The effects of water stress on uptake of mineral elements, especially P, depended on the magnitude and intensity of the water stress (19,20,29,65) and on the concentration of the ion (65,66). Increasing the water stress from -0.4 bar to -5.5 bars had no effect on the accumulation of P or Br in root cells or in xylem sap (29,65).…”

“…Increasing the water stress from -0.4 bar to -5.5 bars had no effect on the accumulation of P or Br in root cells or in xylem sap (29,65). However, the absorption of H"P07 was severely inhibited when water stresses were increased to -12 and -15 bars (20). Nevertheless, translocation of P to the shoots was severely restricted even at relatively low water stresses (Table 4) tion and transport (29).…”

“…They have used solutions with osmotic agents, such as mannitol (18,29,37,42,55,61,65,66,71,73) and polyethylene glycol (PEG) (22,25,26,61,65,66), desiccated roots in air (19,20,61,63) and in pressure plates (18), and limited the amount of roots making contact with nutrient solutions (3,17). Water stresses induced by PEG (PEG 6000) more closely simulated natural water stresses than the stresses induced by mannitol (40).…”