• Influence of Heteromyid Rodents on Oryzopsis hymenoides Germination

      McAdoo, J. K.; Evans, C. C.; Roundy, B. A.; Young, J. A.; Evans, R. A. (Society for Range Management, 1983-01-01)
      Seeds (caryopses) of Oryzopsis hymenoides were a preferred food by species of heteromyid rodents on sandy desert rangelands. The rodents were selective in the type of Oryzopsis hymenoides seeds they put in their cheek pouches, rejecting empty seeds and polymorphic forms with reduced germination. The rodents cached some of these highly germinable seeds and emergence of seedlings from these caches was apparently the primary means of stand renewal of Oryzopsis hymenoides in these plant communities. Captivity studies with heteromyid rodents showed that germination of roughly 50% of the seeds in the caches was greatly enhanced by the rodent's removal of the indurate lemma, palea, and pericarp that induced dormancy. An estimated 0.02% of the Oryzopsis hymenoides seeds produced on a favorable moisture year germinated from rodent caches and emerged as seedlings.
    • Quantity and Germinability of Oryzopsis hymenoides Seed in Lahontan Sands

      Young, J. A.; Evans, R. A.; Roundy, B. A. (Society for Range Management, 1983-01-01)
      The location, quantity, and germinability of seed (caryopses) reserves of Oryzopsis hymenoides (R. & S.) Ricker in the soil were investigated at 4 locations in the Carson Desert of western Nevada. Numerous germinable seeds were recovered from the surface 15 cm of Lahontan sands. There was no clear relation between the number of seeds and depth of burial. On sites with pronounced dunes more seeds were found in the dune sands than in the interspaces. Seeds were recovered with and without evidence of sand abrasion of the indurate lemma and paleas. Seeds without wear marks were much more highly germinable (80%) than the more numerous seeds with wear marks (6%). The germinable seed reserve consisted of seeds that germinated without pretreatment when incubated at 20 degrees C; a much larger portion that required dissection to remove the indurate lemma and palea; and a fraction with embryo dormancy that had to be overcome with gibberellin enrichment of the germination substrate. Large numbers of opened, empty lemma and palea were found in the sands. Rodent enhancement of the germination of Oryzopsis hymenoides seeds appears to be a more valid hypothesis than mechanical abrasion from saltation.