Abstract:

Cenchrus incertus is a noxious invasive weed in Horqin sandy land of Northeastern China. C. incertus is by seed and the seeds are heteromorphic with two phenotypes， a larger mango-shaped type （type M） and a smaller plum-shaped type （type P）. This study explored whether the pericarp of C. incertus has an effect on the germination of heteromorphic seeds， whether the type M seeds has an inhibitory effect on the germination of type P seeds， and whether the germination of two heteromorphic seeds affects the population expansion. In this study， the germination and early seedling growth of M and P type seeds was tested when planted alone or together and imitate the spiniferous bracts （wrapping the two heteromorphic seeds with the cloth again to simulate the spiniferous bracts） ， and the spiniferous bracts under normal condition （only germinating M-type）， single M-type， P-type and P-type seeds in the spiniferous bracts （removing the seedlings from the germinating M-type seeds） were measured to form the seedling growth characteristics. It was found that： 1） The pericarp had no significant effect on the germination of the two heteromorphic seed types. 2） The M type seeds inhibited the germination of P type seeds， the inhibition rate was up to 52.5%. 3） The aboveground biomass and underground biomass of M type seeds in spathes was 0.1298 and 0.1068 g·plant^-1， respectively， greater than P type seeds， and the leaf area and root∶shoot ratios of M type seeds in bracts were， respectively， 84.3% and 356.3% （P<0.05） higher than those of P type seeds. The above studies show： the M type seed in the bract has stronger germinating ability than the P type seed， the M type seed produces seedlings with better survival strategies through more rapid early growth； the P type seed acts as a reserve seed in the current year or the following year to enhance the population numbers.

Key words: Cenchrus incertus, seed heteromorphism, germination strategy, bract, growth characteristic