Melatonin enhances root regeneration, photosynthetic pigments, biomass, total carbohydrates and proline content in the cherry rootstock PHL-C (Prunus avium x Prunus cerasus)

The present study, investigates the effects of melatonin (0, 0.05, 0.1, 0.5,1, 5 and 10 mu M) on the morphogenic and biochemical responses in the cherry rootstock PHL-C (Prunus avium L x Prunus cerasus L.), from shoot tip explants. The incorporation of melatonin (0-10 mu M) in the Murashige and Skoog (MS) medium, greatly influenced rooting either positively or negatively. Melatonin, irrespective of its concentration, had a negative effect concerning the number of roots. However, application of 0.5 mu M melatonin significantly increased the root length: while 1 mu M melatonin increased the root length by 2.5 times, and the fresh weight of the roots by 4 times, in comparison to the control. Although 0.05 mu M melatonin increased rooting by 11.11%, 5 mu M melatonin had a significant reduction on the number, the fresh weight of roots, and the rooting percentage. Melatonin concentration of 0.1 AM resulted in the greatest chlorophyll (a + b) content, and 5 -10 mu M reduced the chlorophyll concentration by 2 times, compared to the control. The high melatonin concentrations (5 and 10 AM), increased the levels of proline and carbohydrates in leaves by 3-4 times. In the roots, 0.5 mu M of melatonin concentration increased the carbohydrate levels by 1.5 times, while 0.05, 0.1 and 1 mu M melatonin concentration significantly reduced the proline content. (C) 2012 Elsevier Masson SAS. All rights reserved.