Laboratory bioassay for phytotoxicity: An example from wheat straw

Allelopathy involves complex plant x plant chemical interactions. Although a large number of laboratory bioassays have proposed to demonstrate allelop athy, most of them have little or no relevance in terms of explaining behav ior in the field. In this paper, we discuss the phytotoxicity of wheat (Tri ticum aestivum L,) straw leachate to the seedling growth of perennial ryegr ass (Lolium perenne L.). The objective of this study was to discuss the sig nificance of (i) soil, (ii) leachate concentrations in bioassays of plant d ebris and soil, (iii) the role of N fertilizer in overcoming plant growth i nhibition, (iv) organic molecules in plant inhibition, and (v) actual assay species. The results show the phytotoxic nature of wheat straw leachate (W SL) and the possible involvement of organic molecules in the growth inhibit ion of perennial ryegrass. However, laboratory studies can not demonstrate allelopathy as the sole factor responsible for the observed growth inhibiti on.