Aquatic humic substances inhibit clastogenic events in germinating seeds of herbaceous plants

One humic acid (HA) and two fulvic acids (FAs) of aquatic origin have been tested for their capacity to inhibit clastogenic events caused by maleic hydrazide (MH) in germinating seeds of the herbaceous plant species Allium cepa and Vicia faba. Either HA or FA at concentrations of 50 and 500 mg L-1 was interacted with 10 mg L-1 MH for 24 h before addition to the seeds. The evaluation of genotoxic activity was made by counting micronuclei (MN) and aberrant anatelophases (AT) in root tip cells after treatment with HA or FA alone, MH alone, and interacted HA + MH and FA + MH. Regular AT were also counted as an index of mitotic activity. In all cases HA and FA nteracted with MH showed an evident anticlastogenic action indicated by the marked reduction of genetic anomalies. In A. cepa, the anticlastogenic effect of HA and FA was more significant for aberrant AT than for MN, whereas the opposite was true in the case of V. faba. The protective effect exhibited for both anomalies by HA was slightly higher than that of the corresponding FA in A. cepa, whereas no significant differences between these HA and FA treatments were observed in the case of V. faba. The two FAs generally showed similar anticlastogenic behaviors with slight quantitative differences observed as a function of the type of anomaly and the plant species. The effects of HA and FA concentration differed depending on the type of anomaly observed, the plant species, and FA origin. In V. faba, cell division, that is, the number of regular AT, was generally depressed by HA and FA at either concentration with respect to the control. In A. cepa, HA and FA produced either stimulating or inhibiting effects on regular AT depending on their nature, origin, and concentration.