Biomass and Biocrude Reponse of Pedilanthus tithymalodies var. Cuculatus to Fe in Calcareous Gomti Entisol

Abstract

In a calcareous Gomti Entisol of Marion, Lucknow, maximum biomass and biocrude response of Pedilalllhus tithymaloides Poil. var. cuculatus was obtained at 50 ug Fe g^-1 soil. A 6-9 folds higher magnitude of Fe response in biocrude than in biomass reaffirmed the indicated role of Fe 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 response to Fe. Critical Fe-deficiency values associated with 66% yield depression, both for soil available and tissue active-Fe, were higher for biocrude than biomas. A decline in the magnitude of biomass response to Fe at maturity, being associated with decreased growth rate in Fe-amended soils !'is a vis control indicated for the existence of some adaptive physiological adjustment mechanism to tolerate the Fe-deficiency stress in the rooting medium.