Abstract
APOT EXPERIMENT was conducted under natural conditions in an open greenhouse to study the allelopathic potentiality of Heliotropium curassavicum and H. bacciferum on the growth parameters of Calotropis procera and Faba sativa. Ground shoot powder with three application rates of 2.5, 5 and 10 g per 8 kg soil for the two Heliotropium species treatment referred as T-1, T-2 and T-3; respectively, were evenly mulched on the soil surface of the test species. The present study showed that the inhibitory effect of H.curassavicum on the growth of the test species was generally more than that of H. bacciferum. Values of root-shoot (R:S) ratios for C.procera treated with either H. curassavicum or H. bacciferum mulches, were less than unity while the same measurements for F.sativa were more than unity. Less number of flowers per individual was recorded in the treated F. sativa in comparison to that of C.procera. Comparing dry matter allocation of C. procera plant organs in most growth stages and treatments demonstrated that, percent allocation of leaves > stem > root > flowers. Dry matter allocation to roots in the case of F. sativa plants treated with either H.curassavicum or H. bacciferum, gave maximum values as compared to other plant organs. Growth analysis of the two test species and the variation in growth criteria in response to the effect of mulching treatments included relative growth rate (RGR), net assimilation rate (NAR), leaf area ratio (LAR), specific leaf area (SLA) and specific leaf weight (SLW) were studied. The RGRs of the two test species generally decreased as the plant age proceeded. The present study recommends the use of the two Heliotropium species for the biocontrol of harmful shrubs such as C. procera and at the same time alerts of the inhibitory effect of these species on the growth of economic plants such as F. sativa.