Germination conditions for Briza subaristata: pretreatments and temperature effects.

The aim of this study was to collect and analyse information about the germ ination patterns of Briza subaristata a native grass of the Humid Argentine Pampa prairie, under different germination temperatures and pretreatments for promoting germination: Mature inflorescences were obtained from Brandse n (Flooding Pampa sub-Region, Buenos Aires Province, Argentina). A three fa ctor completely randomised design with four replications was applied. Treat ments combined prechilling (present or absent), substrate moistened with po tassium nitrate solution (present or absent) and eight germination temperat ures: constant 15 degreesC or 20 degreesC, alternating 15-10 degreesC, 20-1 0 degreesC, 20-15 degreesC, 25-20 degreesC, 30-20 degreesC or 35-20 degrees C in 8/16 hours light/dark periods. Germination values recorded were: perce ntage of germination of normal seedlings (GNS), percentage of dead seeds (D S) and percentage germination of abnormal seedlings (GAS). Two indexes were calculated: days to reach 50% of germination of normal seedlings (TN50) an d mean rate of germination of normal seedlings (R). ANOVA, Tukey and Studen t's t tests as well as correlations were performed. Statistical significanc e was assumed at p<0.05. Alternating temperatures 15-10<degrees>C and 20-10 degreesC prevented normal development of the primary root. The highest per centages of germination of normal seedlings were obtained without prechilli ng, moistening the substrate with KNO3 solution and at constant 15 degreesC germination temperature and with prechilling but no KNO3 at alternating 15 -10 degreesC.