Reducing Seed Dormancy in Indian Ricegrass [Oryzopsis hymenoides]

Abstract

Indian ricegrass [Olyzopsis hy#nt?noties (Roem. and Schuit.) Ricker] is an excellent native species for revegetation of coal and oil shale sites. However, inadequate germination due to a high seed dormancy results in poor stand development and limits its use. This paper presents the results of a series of experiments attempting to reduce the dormancy by weakening the lemma and paiea by scarification of the seed covering. Four treatments (three mechanical nnd one concentrated sulfuric acid) were examined, alone and in combination with gibberellic acid. Three ages of seed were tested in the greenhouse, the laboratory and the field. Concentrated sulfuric acid and a modified commercial scarifier most effectively increased germination in the greenhouse; gibbereilic acid enhanced germination of the younger, fresher seeds in this environment. A rubbing machine improved emergence in the tieid more than the other treatments. It was, however, only a modest improvement. Concentrated sulfuric acid decreased field emergence for ail 3 ages of seed. Germination studies in the laboratory indicated that none of the treatments increased mortality.

Previous Grazing or Clipping Affects Seed of Indian Ricegrass

“…Mechanical scarification of seed caused a significant increase in seed germination of most entries of Indian ricegrass, except for grazed and ungrazed hillside populations. This supported results obtained by Zemetra et al (1983) who found that mechanical scarification increased germination of Indian ricegrass seed. Because of variability in seed weight, size and seed cover thickness, application of a uniform scarification treatment for Indian Seed Germination in a Growth Chamber ricegrass seed is a problem which may explain why some nonuniform germination percentages and stand establishment are obtained.…”

“…This strongly suggested that seed size is an inheritable characteristic in Indian ricegrass, as noted by Zemetra and Cuany (1984). These findings supported work by Bohmont and Lang (1957) and Zemetra et al (1983) who found ecotypic differences in seed weight of Indian ricegrass. Young and Evans (1984) observed a consistent occurrence of a relatively constant ratio of big and small seeds produced by different populations of Indian ricegrass, but polymorphism was not noticeably present in our study.…”

“…Scarification-A modified commercial scarifier, the same one used by Zemetra et al (1983), was used to scarify seeds for the germination experiment. This scarifier used rotating batts to propel the seeds against an abrasive surface.…”

“…High dormancy of Indian ricegrass seed has caused concern for many years and a number of studies have been conducted to investigate dormancy mechanisms and methods for breaking dormancy to improve seed germination of this species (Stoddart and Wilkinson 1938, Toole 1940, Clark and Bass 1970, McDonald and Khan 1977, Zemetra et al 1983, Zemetra and Cuany 1984, Young and Evans 1984, Young et al 1985, Jones and Nielson 1992. Seed dormancy is a mechanism to optimize the distribution of germination over time, and its importance is best illustrated in an ecological context (Bewley and Black 1982).…”

Evaluation of Direct Seeding and Seedling Planting of Two Neotropical Tree Species With the Use of Natural Inputs

“…For the second species, scarified seeds have also been evaluated. The seeds were submitted to scarification in a mechanical device equipped with a cylinder covered by sandpaper during 20 minutes under 1,200 rpm, following the indications of Zemetra et al (1983). For both species potential germination was tested in laboratory and also in a nursery.…”