Hormone-like action of a natural lipid, lysophosphatidylethanolamine: A comparison with auxin

Phospholipids such as lysophosphatidylethanolamine (LPE) are important bio-regulators in plants and animals and have been found to play a critical role in plant growth and development. For example, LPE application has shown to promote fruit shelf life and to retard senescence of plant tissues. Moreover, in vitro plants grown on a calcium deficient media show shoot tip necrosis that leads to a loss of apical dominance. In the present study we investigated the possibility of promoting plant root growth thereby enhancing calcium uptake and maintenance of apical dominance by including LPE in the media. We also compared this action with that of auxin (naphthalene acetic acid ‘NAA’). Nodal cuttings of potato (Solanum tuberosum L. ‘Dark Red Norland’) were cultured on calcium sufficient/deficient media in the presence of LPE (400 ppm) or in the presence of NAA (1 and 2 nM). Inclusion of LPE and NAA in calcium sufficient media improved the overall growth of the plants compared to control (no auxin or LPE in the media). LPE in the root zone was found to increase the adventitious roots initiated at the base of the cultured stem cuttings. Inclusion of LPE, in calcium deficient media, mitigated the calcium deficiency symptoms of potato plants by reducing shoot tip damage and promoting root growth and lateral root formation. This action of LPE was similar to that of NAA when included in the culture media. Our results suggest that LPE may mitigate calcium deficiency symptoms (apex damage) by increasing root growth that in turn increased calcium uptake by the shoot, thus relieving the injury to shoot apex and maintaining apical dominance. Since root growth and apical dominance are known to be regulated by auxin, our results suggest that LPE may act like or interact with this hormone to regulate plant growth and development.