DAILY GERMINATION AND EMERGENCE OF CARYOPSES AND DIASPORES IN NATIVE AND INTRODUCED GRASSES

This work evaluated rate of daily germination (RDG) in caryopses classified by size (CCS) and rate of daily emergency (RDE) in both CCS and diaspores in native grasses, Sideoats grama and Blue grama, and introduced grasses, Buffel and Rhodes. Caryopses were obtained from diaspores and classified by size into small, medium and large. All the propagules were tested by 1) accelerated aging tests (AAT) after sowing caryopses on paper and diaspores in peat moss for 12, 24 and 36 h at 42 degrees C and 100 % HR, and scoring the number of normal seedlings after 15 d; and 2) successful emergence at different sowing depths, by sowing two propagules of each grass at 0.5, 1.0, 2.0, 3.0 and 5.0 cm deep in Vertisol and Calcisol soils, and counting the number of plants after 64 d. The data was analyzed through the LIFEREG (alpha = 0.05) SAS procedure. Differences were observed in RDG and RDE after TAA for native and introduced grasses (P <= 0.001). The highest RDG in Sideoats grama, Blue grama, Buffel grass and Rhodes grass coincided with larger caryopsis, unstressed treatment, and 2 d after sowing (das); yet in native grasses diaspores, highest RDG was obtained from the minimally-stressed treatment, from 4 to 6 das. For introduced grasses, RDG was greater with the minor stress treatment, and it occurred from 6 to 12 d in Buffel and from 5 to 8 d in Rhodes. Sowing depth affected RDE: the highest RDE in any type of propagule was registered between 0.5 and 3.0 cm planting depth, and Vertisol soil promoted higher RDE. Sowing caryopses of larger sizes reduces emergence length and favors establishment of more plants per m(2) under rainfed conditions.