Caryopsis dormancy, germination and seedling emergence in sand, of Leymus racemosus (Poaceae), a perennial sand-dune grass inhabiting the Junggar Basin of Xinjiang, China

Leymus racemosus (Lam.) Tzvel. (Poaceae), wild rye, is an endangered, but economically important, perennial grass. It is mainly distributed in the moving or semistabilised sand in deserts of the Junggar Basin in Xinjiang, China. Freshly harvested caryopses are in non-deep physiological dormancy, causing slow and low germination. Six weeks of cold stratification at 5°C is required for the highest germination percentage to be reached at 25-30°C. Scarifying the fruit coat, or artificial removal of different proportions of the endosperm, also increases caryopsis germination. The greater the proportion of the endosperm that was removed, the higher the percentage of germination reached. However, the dry weight of the seedlings and the rate of root and shoot lengthening were significantly influenced by the proportion of the endosperm that remained on the caryopses. The influences of caryopsis size, or of the proportion of remaining endosperm, on germination and seedling emergence from different depths in sand were studied. The percentage of germination was negatively influenced by burial depth, but not by caryopsis size or the proportion of the endosperm that remained. Seedling emergence was negatively related to both burial depth and caryopsis or endosperm sizes. Seedlings from the smallest seeds or from caryopses with 75% endosperm removed did not emerge from 4 cm, and no seedlings from any of the treatments emerged from a depth of 8 cm.