Inhibition of Germination and Seedling Growth of Eight Forage Species by Leachates from Seeds¹

Abstract

Seeds of many plant species contain phytotoxic compounds which inhibit seed germination or seedling growth of other seeds in their immediate vicinity. Seeds of tall fescue (Festuca arundinacea Schreb.), annual ryegrass (Lolium multiflorum Lam.), orchardgrass (Dactylis glomerata L.), Kentucky bluegrass (Poa pratensis L.), alfalfa (Medicago sativa L.), white clover (Trifolium repens L.), sericea lespedeza [Lespedeza cuneata (Dum. de Cours.) G. Don], and crownvetch (Coronilla varia L.) were leached in water for 24 hours and the leachates were used to moisten filter paper in petri dishes for germination. Seeds of each species were germinated in leachate from all eight species. Seeds of the four legumes were also germinated in leachates from nine other ryegrass cultivars and six other orchardgrass cultivars. Germination and seedling growth of a species was not inhibited by leachate from its own seeds. There was no phytotoxicity to any of the grasses by leachate from other grass species. The only phytotoxicity to any of the grasses was a slight inhibition of bluegrass germination and shoot growth by crownvetch seed leachate. Leachate from one commercial lot of annual ryegrass seed almost completely inhibited germination and root growth of each of the legumes. Other cultivars of ryegrass varied from moderate to no phytotoxicity of their leachates. Leachate of ‘Potomac’ orchardgrass seeds caused moderate germination inhibition of white clover and sericea. Six other orchardgrass cultivars showed little variation in phytotoxicity, while uniformly inhibiting root growth of sericea and crownvetch. Inhibition of germination was not a good measure of phytotoxicity since seedling growth was often inhibited when germination was not.

Aqueous tissue extracts of Conyza canadensis inhibit the germination and shoot growth of three native herbs with no autotoxic effects

“…Dorning & Cipollini (2006) also found an invasive shrub, Lonicera maackii that inhibited seed germination in both native and non-native forbs, without any autotoxicity. For an allelopathic compound to have adaptive value for a plant, the plant should be resistant to autotoxic effects (Cope, 1982;Olson & Wallander, 2002;Inderjit & Duke, 2003). Many different mechanisms exist for the prevention of autotoxicity by allelochemicals in plants, including the conjugation of active compounds with sugars (Inderjit & Duke, 2003).…”

Leaf and root extracts of the invasive shrub, Lonicera maackii, inhibit seed germination of three herbs with no autotoxic effects

“…Extracts of A. altissima also inhibited Lactuca sativa seed germination, but germination of its own seeds was not examined. For an allelopathic compound to have adaptive value for a plant, the plant should be resistant to autotoxic effects (Cope 1982;Olson and Wallander 2002;Inderjit and Duke 2003). A number of mechanisms exist for the prevention of autotoxicity by allelochemicals in plants, including conjugation of active compounds with sugars (Inderjit and Duke 2003).…”

Cultural Management of Weeds in Turfgrass

“…(Peters and Mohammed Zam, 1981; Luu et al, 1982). Leachate from annual ryegrass has a severe inhibitory effect on four forage legume species, and also reduces root length (Cope, 1982). Allelopathic effects of leachates from tall fescue and four other cool‐season turfgrasses occur in Petri‐dish bioassays, but not in soil; therefore, the production of significant amounts of allelochemicals in a field environment is doubtful (Lickfeldt et al, 2001).…”