Autotoxic effects

Organic solvents and water extracts prepared from monoculture wheat soils under conventional tillage (CT) and no tillage (NT) indicated that both soils contain some inhibitory compounds. The CGC/MS/DA of some of the organics is presented. Selected organics from CT and NT as well as allelopathic and autotoxic effects are described and discussed. The relationship between the wheat yields in CT and NT and the possible biological stress is indicated. 

Saxena A, Singh DV, Joshi LN (1996) Autotoxic effects of pearl millet aqueous extracts on seed germination and seedling growth. J Arid Environ 33 255-260... 

Yakle GA, Cruse RM (1984) Effects of fresh and decomposing com plant residue extracts on com seedling development. Soil Sci Soc Am J 48 1143-1146 Young CC, Zhu Thoume LR, Waller GR (1989) Phytotoxic potential of soils and wheat straw in rice rotation cropping systems of subtropical Taiwan. Plant Soil 120 95-101 Yu JQ (2001) Autotoxic potential of cucurbit crops phenomenon, chemicals, mechanisms and means to overcome. J Crop Prod 4 335-348... 

Much research is needed on the quantitative effects on crop yields of interference by most of our serious weeds, and on the relative contributions of allelopathy and competition to the total interference by each weed species. Crop-crop relationships need to be investigated much more thoroughly to determine which crops can follow others with the least inhibitory or most stimulatory effects. More emphasis should be placed on investigations of stimulatory allelopathlc effects, because these effects have been largely Ignored in the past. Possible autotoxicity should be investigated also to determine if it is unwise to cultivate the same crop continuously without rotation. 

Incorporating allelopathy into agricultural management may reduce the use of herbicides, cause less pollution, and diminish autotoxic hazards. Authentic inhibitors isolated from plant material have been subjects for examination in, vitro, but attempts to compare their effects in soils are limited. Soils contain a heterogeneous collection of organic matter of various origins. 

Three lipids A have been more intensively studied in animal models, all of them having indirect effects, mediated in vivo by the immune system. For two of them, DT-5461 and ONO-4007, TNF-a is an important mediator acting at the vascular level that provokes tumor necrosis. For the third one, OM-174, the treatment induces the accumulation of IFN-y and EL-1 P in tumors, which activate NOS II transcription in tumor cells that produce autotoxic NO, which then provokes the apoptosis of tumor cells. At the same time this treatment inhibits the production of TGF-pi by tumor cells which reduces the TGF-pi induced immunosuppression and enhances NO production. Acquired immune response, probably completes the tumor regression started by the apoptosis process and, most probably induces specific memory. 

Crop-crop Interactions. Crop relationships involve both autotoxicity (self-inhibition) and the effects that one crop may have on a different crop. The latter can be stimulatory as well as inhibitory. While the knowledge base for most of these interactions is embryonic, a few examples illustrate their potential. 

Microbially produced phytotoxins also offer several advantages over allelochemicals as herbicides. Allelochemicals from higher plants generally have little selectivity and often are autotoxic to the reproducing species, and, most are not very effective when compared to... 

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