Effects of humic substances on the rooting and development of woody plant cuttings.
Résumé
Humic substances are known to be natural product that could be used as an alternative to artificial fertilizer. The aim of this work was to study the effects of a commercial product containing humic substances, Humyk-Fer (Duclos International), on woody cutting-plant development (Lantana camara). Infrared, fluorescence, atomic absorption and 13C-NMR spectrometry's analysis indicate that Humyk-Fer is com¬posed respectively of 73% and 27% of humic (HA) and fulvic (FA) acids but equally present a high content of metal ions (Fe2+, K+, Na+). The biological effects of Humyk-Fer were then investigated on plant development. Different levels (0, 1, 2 and 4% (v/v)) and various numbers of treatments (1 and 2) were tested in greenhouse for L. camara. First results show that Humyk-Fer drastically increase the growth (170 x), but also reduce the delay of floral transition of L. camara. In addition, a strong reduc¬tion of ferric chlorosis occurred on treated plants. Complementary studies were then conducted to determine the respective functions of HA and FA on growth stimulation as on floral development. In these experiments, agronomic parameters were coupled with molecular analysis of an homeotic MADS-box AGAMOUS-like (AGL) genes. Preliminary results seem to suggest that AGL gene is up-regulated by humic acid treatment suggesting that low amount of humic substances increase plant organo¬genesis, and probably flower development.