Allelopathic Effect of (Casimiroa edulis Llaveet Lex.) Leaf Extracts on Germination and Seedling Growth of Maize (Zea mays L) and Sorghum (Sorghum bicolor (L) Moench)

Abstract The changes over time of both composition and quantity of allelochemicals can either increase or decrease the phytotoxicity of decomposing plant litter. The present study was undertaken to investigate the allelopathic effects of leaf extracts of C. edulis on sorghum and maize seed germinations. The aqueous extract of white sapota (Casimiroa edulis L1ave & Lex) leaf samples were used as a source of allelochemicals. Data collection involved the germination and seedling growth parameters including Germination rate (GR); germination inhibition rate GIR); MGT: mean germination time (MGT); germination index (GI); Relative length of plumule (RLP); germination speed (v); relative length of radicle (RLR); plumule inhibition rate (PIR); radicle inhibition rate (RIR); allelopathic index (AI). The result indicated that highest concentration of the allelopathic extract (20 mg/L) has demonstrated significantly the highest germination inhibition rate (56.67%) for sorghum; GIR (36.67%) and MGT (3.90 days) for maize seeds, while the highest PIR (76.05%) and RIR (89.60%) for sorghum, as PIR (56.79%), RLR (80.09%) for maize seeds. The allelopathic intensity was found to be the highest (50%) for sorghum, and (36.67%) for maize seed germination. For sorghum seed germination, the first principal component (PC1) has got high positive loads from germination rate (0.36), RLP(0.36), AI(0.36), RLR (0.35), and GI (0.31). The PC2 has got the highest positive load (0.67) from germination speed, but high negative load from MGT(-0.68). In allelopathic effect on maize seed germination, PC1 has got highest scores from AI (0.51), and GI (0.51), but highest negative scores from relative length of plumule (-0.51). It can be concluded that the highest negative scores in PCs which is GIR indicate direct relationship between the negative allelopathic index and negative score factors. However, the highest positive scores in PCs indicate positive AI in both sorghum and maize seed germinations.