Germination of Seeds of 'Paloma' and 'Nezpar' Indian Ricegrass

Abstract

Seedlots of the cultivars ‘Paloma’and ‘Nezpar’ Indian ricegrass [Oryzopsis hymenoides (R. & S). Ricker] were classified as to seed type, germination, and germination in response to the additive enhancement treatments of removing the lemma and palea by dissection, enriching the germination substrate with gibberellin (G&), and cool-moist stratification at 2’C for 2 weeks. The seedlots contained different proportions of polymorphic seed size, color, and covering types. Seedlots of ‘Paloma’were dominated by big black seeds while lots of ‘Nezpar’ contained roughly equal propertions of big and small black seeds. The various seed types had different germination characteristics both under control and enhancement treatments. The initial germination of untreated seeds of either cultivar was very low; however, maximum germination with enhancement did not exceed 5%. Indian ricegrass [Oryzopsis hymenoides (R. & S.) Ricker] is the dominant perennial grass species of salt desert ranges occurring at lower elevations within the sagebrush (Artemisiu) vegetation zone of western North America. On sand dunes Indian ricegrass may form relatively pure stands, sometimes several thousand hectares in extent. Being a widely occurring valuable forage species and a monospecific dominant of harsh, arid environments, Indian ricegrass has received considerable attention from agronomists and range managers as a potential revegetation species (Robertson 1976). Recently, interest in this species has increased because of the importance of revegetating sandy-textured spoils from mining operations. Indian ricegrass seeds (caryopses) are highly polymorphic, but all forms are generally dormant (Huntamer 1934). The nature of the dormancy has been attributed to the persistent lemma and palea and pericarp that probably inhibit oxygen transfer to the embryo (Huntamer 1934, Fendal 1964, Clark and Bass 1970, Shaw 1976, McDonald and Kahn 1977, Zemetra 1979). The lemma and palea have to be removed and the pericarp pricked in order for the seeds to germinate. A form of embryo dormancy that gradually breaks down over time, but can be overcome by cool-moist stratification, has also been documented for Indian ricegrass seeds (Tooele 1940, Clark and Bass 1970). The cool-moist stratification requirement of some lots of Indian ricegrass seeds can be partially or totally substituted by adding gibberellic acid to the germination substrate (McDonald and Kahn 1977). Our purposes were to determine whether different seed types could be identified in seedlots of ‘Paloma’ and ‘Nezpar’ Indian ricegrass and whether these seed types have different germination with and without enhancement treatments.