OIL TREATMENT AND DIGESTION DEPRESSES GERMINATION OF GRASS SEED

Numerous grasses, including Panicum spp., produce seed that survive pa ssage through the digestive system of livestock and germinate in the f eces. Managing livestock to distribute viable seed of desirable plants is a means of revegetating degraded grasslands. Potential germination of grass seeds declines with increased resident time in the gastroint estinal tract. Loss of seed germinability with increased resident time may be caused by indirect effects of secondary metabolites of digesti on on the embryo. The cause of the loss of seed germinability is not k nown, nor is the identity of the secondary metabolites. We hypothesize d that coating seed with oil would reduce damage caused by these secon dary metabolites. Our objective was to elucidate the effect of oil tre atments on germination of Panicum ssp. seed following in vitro and in vivo digestion. TEM-LD1 kleingrass (P. coloratum L.) and 'Alamo' and ' Sunburst' switchgrass (P. virgatum L.) seeds were evaluated in a serie s of trials with and without pretreatment with oil. Corn (Zea mays L.) and mineral oil without subsequent digestion had a small negative eff ect on germination. Duration of seed exposure to oil or oil type had n o effect on seed germination. However, oh pretreatments significantly reduced germination of digested seed of both species in all trials. Mi neral oil reduced germination more than corn oil, and increased exposu re time to oil prior to digestion further depressed (up to fourfold) s eed germination. Apparently, oil treatment solubilized the protective layer of the seed coat, thereby enhancing the digestion effect on the seed embryo. These differential responses may help elucidate the natur e of the protective mechanism of the seed against digestion effects. W e conclude that oil treatment cannot be used to protect these seeds fr om digestion effects.