Growth responses and factors affecting tillering of Andropogon hallii (Hack.)

Sand bluestem, Andropogon hallii (Hack.), is a native, perennial grass of tropical origin. Effects of several combinations of temperature (25, 30, and 35°C) and photoperiod (8, 12, and 16 hours) on germination, seedling survival, and seedling growth of an accession, G-1773, of sand bluestem were determined in environmental chamber studies. These results were compared with those obtained from similar studies with grasses of nontropical origin by other researchers. Effects of selected plant growth regulators on rate of tillering and seedling growth of G-1773 sand bluestem were determined. Germination of G-1773 sand bluestem was affected by temperature, but not by light or photoperiod. Highest germination was obtained from caryopses exposed to high alternation temperatures. Seedling survival was favored by low temperatures and 12-hour photoperiods. No seedlings survived to the end of the 10 week experimental period under the high temperature and short photoperiod used in this experiment. Extended leaf height and dry matter production of all plant components were greatest under 12-hour photoperiods. Dry matter production was highest under low temperatures, while tallest plants were produced under moderate temperatures. No differences in phytomer initiation or internode elongation were recorded. Development of axillary buds into tillers occurred at only 2 of the 9 temperature and photoperiod combinations. A few tillers appeared on plants grown under 25°C - 12 hours, but more than 5 times as many developed on plants grown under 30°C - 12 hours. Accumulation of carbohydrates was closely related to tillering. Tillering of G-1773 sand bluestem was accelerated by relatively low concentrations of Ethrel and DPX-1840. Larger numbers of tillers developed on plants treated at the 2-leaf stage as compared with those treated at the 6-leaf stage. Tiller length, plant height, and dry matter production were often reduced by application of plant growth regulators. Plant form also was altered by DPX-1840