Research articleMelatonin enhances root regeneration, photosynthetic pigments, biomass, total carbohydrates and proline content in the cherry rootstock PHL-C (Prunus avium × Prunus cerasus)
Highlights
► Melatonin at concentrations of 0.05–1 μM positively influenced root elongation of the PHL-C rootstock. ► High melatonin concentrations significantly increased carbohydrates and proline level of leaves of the PHL-C rootstock. ► Rooting of the PHL-C rootstock was inhibited when high melatonin concentrations (5–10 μM) were added in the substrate. ► Chlorophyll and porphyrins concentration substantially increased with 0.1 and 0.5 μM melatonin.
Introduction
PHL-C (Prunus avium L. × Prunus cerasus L.) is a dwarfing rootstock which is a hybrid originating in the Czech Republic. Its compatibility with all sweet cherry varieties tested is excellent. Varieties budded on this rootstock are 50–60% less vigorous than those on seedling rootstocks, and 10–15% more vigorous than on Gisela 5 (P. cerasus × Prunus canescens). Furthermore, this rootstock is tolerant to waterlogging, calcareous soils, Agrobacterium tumefaciens and Pseudomonas syringae. Today, it is recommended for high density plantings (600–800 trees/ha) and for cultivation under cover.
Melatonin (5-methoxy-N-acetyltryptamine) is a ubiquitous acting molecule in animals and plants. Melatonin was discovered in edible plants in 1995 [1] and has been found in more than 100 plant species [2].
Since melatonin is an indoleamine, it may have typical auxin-like functions, such as the regulation of morphogenesis and an increase in de novo root formation [3]. A recent study by Sarropoulou et al. [4] indicated that melatonin promotes rooting in the explants of the sweet cherry rootstocks CAB-6P, Gisela 6 and M × M 60. Melatonin also affects regeneration of the lateral root system and adventitious roots in Lupinus albus seedlings, and promotes rooting when added together with indole acetic acid (IAA) [5].
Melatonin is a molecule with powerful scavenging activities in reactive oxygen and nitrogen species [6]. One important function of melatonin is the scavenging of free radicals, thereby protecting plants against oxidative stress or any stressful condition at the cellular level, and reducing the damage to the macromolecules [7], [8].
The aim of the present study was to test the possible effects of melatonin in the rooting, photosynthetic pigments, total carbohydrates and proline of one commercial cherry rootstock, namely PHL-C. The parameters for evaluation included the effects of melatonin on the rooting percentage, root number per rooted explant, root length, root fresh weight, and concentration of total chlorophyll (a + b), carotenoids, porphyrins, carbohydrates and proline.
Section snippets
Results
In the rootstock PHL-C, the greatest number of roots per rooted explant (5) was recorded in the control plants (Fig. 1, Fig. 9A). Therefore, melatonin, irrespective of its concentration, had a negative effect concerning the number of roots. This occurred even at the lowest concentration of 0.05 μM (Fig. 9B). However, the application of 0.5 μM melatonin significantly increased root length (Fig. 2), although it decreased the number of roots per rooted explant (Fig. 9C). The maximum root
Discussion
Our data indicate that melatonin positively affects the length, fresh weight of roots and rooting percentage at a 1 μM concentration in the rootstock PHL-C. Melatonin induced root growth, is determined by two nearly simultaneous auxin modulated physical processes, such as water uptake and irreversible cell wall extension [9]. In contrast, melatonin in all tested concentrations had a negative impact on the number of roots per rooted explant. In comparison to the cherry rootstocks CAB-6P (
Plant material and culture conditions
The effect of melatonin was studied in in vitro experiments employing the cherry rootstock PHL-C (P. avium L. × P. cerasus L.). Seven treatments of melatonin (0, 0.05, 0.1, 0.5, 1, 5 and 10 μM) were included in the experiment and each treatment 9 replicates (tubes). As regards plant material, shoot tip explants from previous in vitro cultures of 1.5–2.5 cm in length were used. The explants were grown in glass tubes with a flat base of 25 × 100 mm containing 10 mL of Murashige and Skoog medium
Acknowledgements
We would like to express our sincere gratitude to Angelos Xylogiannis for kindly providing the PHL-C (Prunus avium × Prunus cerasus) plants; also our thanks to S. Kuti and V. Tsakiridou for technical assistance. The authors gratefully acknowledge the financial support of the Aristotle University of Thessaloniki.
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