EFFECTS OF RESPIRATION INHIBITORS ON ACCUMULATION OF RADIOACTIVE PHOSPHORUS BY ROOTS OF LOBLOLLY PINE

Abstract

Mycorrhizal and non-mycorrhizal roots of loblolly pine (Pinus taeda) were immersed in 0.001 [image] NaN3, 0.005 [image] NaF, and 0.025 malonic acid for a conditioning period of 1 hr., then transferred for 3 hrs. to inhibitor plus p32 having an activity of about 300 [um]c. per liter. The pH of the system had a marked effect on the action of all 3 inhibitors. Azide reduced accumulation to a greater extent in non-mycorrhizal roots at all pH values. The inhibition was almost complete at pH 4.7, but much less at pH 5.7-5.8. Fluoride almost completely inhibited accumulation at the lower pH, but increased it above the controls at the higher pH. Malonic acid did not significantly reduce accumulation of P32 at the lower pH, but increased it above the controls at the higher pH. In general the inhibitors tested reduced accumulation of P32 by pine roots much as they have been shown by other workers to reduce respiration of barley roots, although barley roots appear somewhat more sensitive to malonic acid than are pine roots. It is probably that the reduction in accumulation of P32 is the result of reduction in root respiration. Apparently mycorrhizal roots are less sensitive to azide and fluoride than non-mycorrhizal. The amt. of P32 adsorbed on the surfaces of root segments was not large enough to constitute a serious source of error.