Phytotoxic substances

It is unlikely that any one particular compound could be responsible for reduced weed growth in no-till. Higher plants and microorganisms produce a myriad of phytotoxic substances. If these substances are present in the right combination and concentration, phytotoxic effects may be observed. With the proper choice and management of various cover crops and plant residues, it may be possible to supplement if not reduce the number and amount of... 

Guenzi, W.D., Kehr, W.R., and McCalla, T.M., Water-soluble phytotoxic substances in alfalfa forage variation with variety, cutting, year and stage of growth, Agron. J., 56, 499, 1964. 

Toussoun, T.A., Patrick, Z.A. Effect of phytotoxic substances from decomposing plant residues onrootrot of bean. Phytopathology 1963 53 265-270. 

Solanapyrones were isolated as phytotoxic substances from phytopathogenic fungi Altemaria and... 

Lithium must rather be considered as a potentially phytotoxic substance, with marked species-dependent differences in sensitivity. Even very small quantihes of lithium ions in the nutrient solution can rapidly manifest themselves in leaf chlorosis (Bach... 

Norstadt and McCalla (1968) observed the formation of patulin, a potent phytotoxic substance, in soil amended with wheat straw. This was apparently produced by Penicil-lium urtricae Bainier, since the presence of the residues favored growth of the fungus, and phytotoxicity increased with growth. 

Unfavorable effects of mulches, occasionally observed, are most likely to result from deficiencies of nitrogen, and sometimes of phosphorus, that may occur under mulches of materials of wide carbon—nitrogen ratios. Mulches may also be a source of phytotoxic substances naturally present or synthesized by certain microorganisms that are active in their decomposition (see Chapter 18). 

McCalla TM, Haskins FA (1964) Phytotoxic substances from oil micro-organism and crop residues. Bact Rev 28 181-207... 

Greenland DJ (1965) Interactions between clays and oiganic compounds. Part I. Mechanisms of interactions between clays and defined organic matter. Soil Fertil 28 415-425 Greenland DJ (1971) Interactions between humic and fulvic acids and clays. Soil Sci 111 34-41 Guenzi WD, McCaUa TM (1966) Phytotoxic substances extracted from soil. Soil SciSoc Am Proc 30 214-216... 

Patrick ZA (1971) Phytotoxic substances associated with the decomposition in the soil of plant residue. Soil Sci 111 13—18... 

Me Calla, T. M., and F. A. Haskins. 1964. Phytotoxic substances from soil microorganisms and crop residues. Bacterial. Rev. 28(2) 181-207. 

Aluminium compounds contained in rocks, soil and sediments are very slightly soluble, and in natural waters very low concentrations of aluminium occur (mostly <20(xg/l). Aluminium ions are easily hydrolysed even in neutral media and form insoluble multinuclear complexes of either aluminium ions or aluminium hydroxide Al(OH)3. In addition, in a soil solution at neutral pH, the aluminium concentration is low and its intake by plants is very limited. For example, soil acidification by acid rain increases the solubflity of aluminium compounds and aluminium can thus enter the hydrosphere and biosphere in higher amounts. In sHghtly acidic solutions (pH 5), the predominant cations are [Al(OH)2]" > [Al(H20)g] + > [Al(OH)] +. Under these conditions, aluminium is actually toxic to certain organisms. A higher intake of aluminium by birds leads to abnormalities of their eggs. Soluble compounds of aluminium in plants cause slower growth, because aluminium is a phytotoxic substance. 

---