The growth response of castor oil plant,
Ricinus communis
, in spent lubricating oil (SLO) was investigated using 1-6% w/w SLO and a control. The result showed that highest percent germination of approximately 92, was obtained in control and the least in 5% w/w. The early germination obtained in this study was significant when considered in the light of reported delay and depression of germination by spent lubricating oil in
Capsicum annum
,
Lycopersicon esculentum
,
Solanum melongena
and
S. incanum. For parameters like plant height, stem girth, leaf area, fresh and dry weights, and root length, the mean values obtained were higher for 1% w/w than control. There was stimulation of growth at 1% w/w spent lubricating oil in soil. Plants in higher concentration (2 - 6% w/w) exhibited depression in growth. Plants grown in 1% w/w spent lubricating oil in soil flowered earlier than those grown in control. A difference of eight (8) days was observed. @JASEM
