Green needlegrass Stipa viridula (native through North America from southern Canada to southern USA) is commonly used in rangeland seedings and revegetation of human-disturbed areas in the northern Great Plains. This study was conducted to determine the influence of planting depth, seed variety, and temperature on morphology and emergence of needlegrass seedlings.
‘Lodorm’ (a green needlegrass variety with reduced seed dormancy) and accession ‘SD-93’ were used. Seeds were planted at soil depths of 1.5, 3, 4.5, 6 and 7.5 cm in pots (20 cm diameter x 20 cm deep) and placed in growth chambers at a 20/15ºC (15 h light/9 h dark) or 25/20ºC temperature regime (these temperatures simulate spring growing conditions) in a randomized block design with factorial arrangement of treatments (4 replications).
Emerged seedlings (i.e. leaf visible at soil surface) were counted daily for 14 days from planting. The first five emerging in each pot were marked. On day 14, pot soil was placed on a screen and washed from seedling roots. Marked seedlings were removed and killed (in a 5% acetic acid solution). Data recorded from marked seedlings were: 1) coleoptile length; 2) subcoleoptile internode length; 3) seminal root length; 4) coleoptilar node to tip of longest leaf length; and 5) number and length of adventitious roots per seedling.
Coleoptile length increased with planting depth. Seminal primary root length, adventitious root length and number of roots decreased with planting depth. SD-93 seedlings had shorter subcoleoptile internodes, longer coleoptiles and better root development than Lodorm seedlings.
Seedlings under the warmer regime had better root development than those under the cooler regime, but reach of the coleoptile above planting depth was not as great.
Overall, results indicated that green needlegrass should generally not be planted at depths greater than 3 cm because of lower percent emergence, lower rate of emergence, and poor root development of seedlings emerging from greater depths.