AUXIN-LIKE EFFECT OF HUMIC SUBSTANCES EXTRACTED FROM FECES OF ALLOLOBOPHORA-CALIGINOSA AND ANTENNARIA-ROSEA

Leaf explants of Nicotiana plumbaginifolia were compared in cultures supplemented with IAA, inhibitors of IAA (TIBA = 2,3,5-triiodobenzoic acid and PCIB = 4-chlorophenoxy-isobutyric acid) and a humic substance (HEf) obtained from the faeces of Allolobophora caliginosa and A. rosea. The results show that HEf at a concentration of 1 mg Cl-1 causes root development from leaf explants that appears to be similar to IAA-induced activity, while the control did not develop roots. Furthermore HEf induced longer roots than those grown in IAA with fewer hair roots. in the presence of the IAA inhibitors, the leaf explants were without roots. Humic matter, IAA and IAA-inhibitors stimulated peroxidase activity in N. plumbaginifolia. Also, when the Nicotiana tissues were treated with the humic fraction and IAA there was a minor polymorphism in the esterase isoenzymes. The presence of both TIBA and PCIB restored the esterase profile obtained from control tissues. The induced root-forming activity in leaf explants and the minor polymorphism with respect to the control in the esterase zymograms demonstrate that the humic substance exhibited auxin-like activity. HEf, a low molecular size fraction, was obtained from the faeces of Allolobophora caliginosa (Sav.) and A. rosea (Sav.) by disaggregating the humic material with acetic acid, confirmed the effectiveness of the combination of high acidity and low molecular size in influencing the biological activity of the plant system tested.