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.
Soybean [Glycine max (L.) Merr.] seed lots were evaluated for emergence, stand, and yield. Seven cultivars were analyzed in 1975 and eight in 1976. The seeds were planted 3.8 cm deep at a rate of 6 seeds/0.3 m of row in sandy and heavy type soils. Three planting dates — early, pre‐optimum, and optimum — and four replicates were used for the evaluations. Emergence counts (V2 to V3 growth stage) and stand counts (R6 growth stage) were recorded for the planting dates and sites. Yield was determined on 4.9 m of row for seeds planted on the optimum planting date in the heavy type soil.Each year, seedling emergence and stand were better on a sandy type soil than on the heavy soil and were best for the optimum date of planting. Simple correlation coefficients of emergence and stand counts for both years were high and significant. However, analysis of variance showed seed lots did not perform similarity across sites and planting dates in 1975. A 10 to 15 percentage point difference in emergence was necessary for a significant difference between seed lots, depending on site and planting date. In 1975 and 1976 the correlations between stand and yield were low, rr= 0.361 and 0.311, respectively, but those between stand and yield/plant were high and negative, r = −0.862 and −0.830, respectively. Stand and yield for the cultivar ‘Wayne’ were significantly correlated each year.
Panicle emergence, anthesis and several components of seed yield of 42 S1 (Lolium perenne L. ✕ Festuca arundinacea Schreb.) × Festuca arundinacea Schreb. hybrid clones, grown at Prosser, Washington, and Lexington, Kentucky, were studied in two different years to evaluate seed production capabilities in widely diverse environments.Clones differed at both locations for time of panicle emergence, date of anthesis, percent fertile pollen, number of panicles per clone, seed yield per clone, seed yield per panicle, percent fertile florets, and weight of 100 seeds. Total panicle production per plant at Prosser was approximately nine times greater than at Lexington, a factor that helped to explain the higher seed yields obtained at Prosser during both years.The widely diverse environments resulted in significant differences between locations and significant clone and location interactions for most characters studied.A correlation analysis between locations of means for characters of the 42 individual clones showed a highly significant association during both years for: (a) percent fertile pollen (r=0.87, r=0.80); (b) percent fertile florets (r=0.83, r=0.77); (c) seed per panicle (r=0.79, r=0.71); and (d) total seed yield per clone (r=0.67, r=0.72).
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