Seed Appendages and Germination of Two Asiatic Bluestems1

Abstract Establishment of several grass species is difficult because of seed dormancy. The objective of this research was to evaluate the inhibitory effects on germination of substances from the bracts (glumes, lemma, palea), which enclose the caryopses of two Asiatic bluestems, Bothriochloa ischaemum (L.) Keng var. ischaemum (‘M’ strain) and B. intermedia (R. Br.) A. Camus (‘T’ strain). Standard germination tests demonstrated that the germination capacity of caryopses of both strains freed of appendages by hand was significantly greater than that of the rough seed units. Ether‐soluble inhibitors were present in aqueous refluxed material from empty bracts of both strains. The heavy oily residue of this extract after ether evaporation significantly retarded seedling growth in both strains. Ether extracts from empty bracts subjected to a 72‐hour 65 to 70 C heat treatment did not inhibit germination of lettuce seed. Ether‐soluble inhibitors in the untreated bracts were heat liable and concentration‐dependent for inhibition effects. The inhibition of germination in fresh seed of both species was caused, at least in part, by substances within the bracts. Heat drying appeared to cause a degradation of these biologically active compounds(s). Thin‐layer chromatography showed that certain compound(s) were immediately or progressively lost with each increment of treatment duration. Appropriate drying of the rough seed units prior to planting would reduce the inhibitory effects of natural ether‐soluble components within the bracts and increase the probability of stand success.