Allelopathic activity of a testa-derived solution from Siberian Maple (Acer ginnala Maxim.) seeds

We have studied the endogenous secondary metabolites present in the testa layers of Siberian maple (Acer ginnala Maxim.) fruit. We examined physical and chemical properties (specific gravity, light absorbance) of the testa-derived solution ‘osmoticate’, media conditions (pH, phytagar concentration) and the testa structure before and after the rehydration using scanning electron microscopy (SEM). We examined in vitro, the effects of osmoticate on the seed germination and seedling development of both monocots [fescue (Festuca rubra L.)], dicots [tomato (Lycopersicon esculentum Mill.) and lettuce (Lactuca sativa L.)]. In addition to the species examined here, other organisms were tested in preliminary bioassays, including single-celled alga (Oscillatoria and Oedogonium; Carolina Biological) by adding varying concentrations of osmoticate to algal cultures. Low concentrations of osmoticate showed a stimulatory effect, indicating that perhaps the osmoticate was providing additional nutrients or, not surprisingly, that the osmoticate contains low levels of plant growth hormones (19). The effects of higher concentrations of osmoticate have been inconclusive.

All three test species showed impaired root development: root length was less in tomato; root orientation was abnormal in lettuce; while in fescue, secondary root development dominated the primary root length (near zero). Besides, we also examined the effect of the osmoticate on A. ginnala seed germination. Mostly seeds remained dormant in the presence of this soluction, osmoticate. These results strongly suggest that osmoticate may contain powerful, multi-functional allelochemical(s) that inhibit development of the competitors in the plant community and also simultaineously regulate the germination of Siberian maple.