Study On Allelochemicals Of Subterranean Part Of Sorghum Halepense(L.) Pers.

Johnsongrass [Sorghum halepense (L.) Pers.], a grass weed of Sorghum moench, in the family of poaceae, has caused serious economic and social harm around the world. Its rhizomes growth rapidly and have strong reproductive capacity. They could product 70 m in a growing season and each joint can form new plants. The allelopathic potential and allelochemicals of subterranean part of Sorghum halepense (L.) Pers. were investigated for finding potential allechemicals, and determining their chemical basis and ecology meanings.1)The allelopathic potential of Sorghum halepense (L.) Pers. was investigated by studying the effects of its subterranean parts (rhizome and fibers) on the germination and growth of Lactuca sativa, Solanum lycopersicum, Digitaria sanguinalis and Triticum aestivum. The subterranean parts were either extracted with water or mixed the pulverized tissues with soil. At 0.08 g/mL, water-extracts from the rhizome and the whole subterranean tissue inhibited 100% germination of Lactuca sativa on the first day after sowing, while at 0.02 g/mL and 0.04 g/mL, water-extract from the fibrous roots inhibited 12.00% or 42.66% germination. At 0.08 g/mL, on the fifth day, the inhibition effects of water-extracts from rhizome, the whole subterranean tissue and fibrous root, on the fifth day, declined to 67.42%, 70.79% or 10.11% respectively. The inhibition effects of water-extracts from the 3 underground tissues on the germination of other seeds tested showed the same tendency, that the inhibition was strengthened with the increased concentration, weakened with increased treatment time. The water-extracts from rhizome had greater inhibition on L. sativa, S. lycopersicum and D. sanguinalis germination than that from fibrous root, while that from fibrous root showed stronger inhibition on T. aestivum germination. Each material that mixed into soil inhibited T. aestivum germination and seedling growth, the inhibition effect of fibrous root was greater than that of rhizome.2) By spectroscopic (MS, NMR) analysis, eight compounds were identified: ethyl p-hydroxybenzoate, p-hydroxybenzaldehyde, tricin, diosmetin, luteolin, apigenin, p-hydroxybenzoic aid, dhurrin3) The activity of the compounds were tested by bioassay. All compounds decreased the germination speed index of Lactuca sativa seeds with the exception of p-hydroxybenzaldehyde and luteolin. Ethyl p-hydroxybenzoate demmonstraed the strongest delaying effect among phenols, similar effect was found with apigenin among flavinoids. All substances inhibited shoot and root growth of Lactuca sativa. The inhibition of ethyl p-hydroxybenzoate, p-hydroxybenzaldehyde, p-hydroxybenzoic aid, diosmetin, apigenin, luteolin and dhurrin was 75.12%, 93.77%, 47.21%, 45.26%, 55.74%, 64.86%, 64.86% to shoot growth and 86.57%, 92.17%, 54.88%, 39.54%, 69.96%, 82.33, 79.41% to root growth at 3.0 mM, respectively.