BIOMASS AND BIOCRUDE RESPONSE OF PEDILANTHUS-TITHYMALODIES VAR CUCULATUS TO FE IN CALCAREOUS GOMTI ENTISOL

In a calcareous Gomti Entisol of Marion, Lucknow, maximum biomass and biocrude response of Pedilanthus tithymaloides Poit. var. cuculatus wa s obtained at 50 mug Fe g-1 soil. A 6-9 folds higher magnitude of Fe r esponse in biocrude than in biomass reaffirmed the indicated role of F e in the biosynthesis of biocrude hydrocarbons, specially the resinous methanol and acetone extractives. DTPA-NH4-HCO3 (pH 7.6) extractable available and tissue active-Fe were better indicators of plant respons e to Fe. Critical Fe-deficiency values associated with 66% yield depre ssion, both for soil available and tissue active-Fe, were higher for b iocrude than biomas. A decline in the magnitude of biomass response to Fe at maturity, being associated with decreased growth rate in Fe-ame nded soils vis a vis control indicated for the existence of some adapt ive physiological adjustment mechanism to tolerate the Fe-deficiency s tress in the rooting medium.