Kortessa Dimassi-Theriou

Melatonin promotes adventitious root regeneration in in vitro shoot tip explants of the commercial sweet cherry rootstocks CAB‐6P (Prunus cerasus L.), Gisela 6 (P. cerasus × P. canescens), and MxM 60 (P. avium × P. mahaleb).

Abstract:  The objectives of this study were to test the effects of melatonin (N‐acetyl‐5‐methoxytryptamine), a natural compound of edible plants on the rooting of certain commercial sweet cherry rootstocks. Shoot tip explants from previous in vitro cultures of the cherry rootstocks CAB‐6P (Prunus cerasus L.), Gisela 6 (P. cerasus × P. canescens), and M × M 60 (P. avium × P. mahaleb) were included in the experiment. The effect of indole‐3‐acetic acid (IAA) and indole‐3‐butyric acid (IBA) alone or in combination with melatonin was tested concerning their rooting potential. Seven concentrations of melatonin (0, 0.05, 0.1, 0.5, 1, 5, and 10 μm) alone or in combination with 5.71 μm of IAA or 4.92 μm of IBA were tested. For each rootstock, 21 treatments were included. The explants were grown in glass tubes containing 10 mL of substrate. The parameters measured include rooting percentage, number of roots per rooted explant, root length, and callus formation. The data presented in this study show that melatonin has a rooting promoting effect at a low concentration but a growth inhibitory effect at high concentrations. In the absence of auxin, 1 μm melatonin had auxinic response concerning the number and length of roots, but 10 μm melatonin was inhibitory to rooting in all the tested rootstocks. The final conclusion of this experiment is that exogenously applied melatonin acted as a rooting promoter and its action was similar to that of IAA.

Volatile Constituents and Antioxidant Activity of Peel, Flowers and Leaf Oils of Citrus aurantium L. Growing in Greece

The volatile constituents of the essential oils of the peel, flower (neroli) and leaves (petitgrain) of bitter orange (Citrus aurantium L.) growing in Greece were studied by GC-MS. The analytical procedures enabled the quantitative determination of 31 components. More specifically, the components of the essential oils identified were: twelve in the peel, twenty-six in the flowers, and twenty and sixteen in old and young leaves, respectively. The major constituents of the different parts of Citrus aurantium L. essential oils were: β-pinene (0.62%–19.08%), limonene (0.53%–94.67%), trans-β-ocimene (3.11%–6.06%), linalool (0.76%–58.21%), and α-terpineol (0.13%–12.89%). The DPPH test demonstrated that the essential oils in the old leaves had the maximum antioxidant activity, followed by the flowers, young leaves and the peel in that order. This study updates the data in the literature on the essential oils of bitter orange, and provides information on the composition of the oils for a further evaluation of this product.

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

The present study, investigates the effects of melatonin (0, 0.05, 0.1, 0.5, 1, 5 and 10 μM) on the morphogenic and biochemical responses in the cherry rootstock PHL-C (Prunus avium L. × Prunus cerasus L.), from shoot tip explants. The incorporation of melatonin (0-10 μM) 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 μM melatonin significantly increased the root length; while 1 μM 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 μM melatonin increased rooting by 11.11%, 5 μM melatonin had a significant reduction on the number, the fresh weight of roots, and the rooting percentage. Melatonin concentration of 0.1 μM resulted in the greatest chlorophyll (a + b) content, and 5-10 μM reduced the chlorophyll concentration by 2 times, compared to the control. The high melatonin concentrations (5 and 10 μM), increased the levels of proline and carbohydrates in leaves by 3-4 times. In the roots, 0.5 μM of melatonin concentration increased the carbohydrate levels by 1.5 times, while 0.05, 0.1 and 1 μM melatonin concentration significantly reduced the proline content.

Effects of light, magnesium and sucrose on leaf anatomy, photosynthesis, starch and total sugar accumulation, in kiwifruit cultured in vitro

Shootlets of kiwifruit plants (Actinidia deliciosa) were culturedin vitro. Combinations of light intensity, Mg and sucrose in the cultures showed that an increase of light intensity resulted in a corresponding increase of the relative size of the leaf mesophyll cells and in a decrease of the numbers of chloroplasts and contained starch grains. The addition of sucrose to the substrate media negatively affected the size of the mesophyll cells under normal Mg concentration (35 mg l−1), and positively under high Mg concentration (105 mg l−1 ). Sucrose further resulted in an increase in the numbers of chloroplasts and contained starch grains. The photosynthetic capacity of leaves greatly increased when Mg concentration was enhanced and sucrose was excluded from the nutrient substrate. Total sugar accumulation in all treatments was favoured by normal light intensity and addition of sucrose.

Effect of melatonin, salicylic acid and gibberellic acid on leaf essential oil and other secondary metabolites of bitter orange young seedlings

An investigation was carried out in order to estimate the biochemical changes occurring in bitter orange (Citrus aurantium L.) leaves in response to melatonin (MEL), gibberellic acid (GA) and salicylic acid (SA) treatments. We examined the effect of MEL, GA and SA on the essential oil (EO), the total phenolic (TPC) and total flavonoid content (TFC), and the antioxidant activity of bitter orange leaves from 1-year-old plants. 15 μMMEL, 1 mMSA and 1.44 mMGA increased the total leaf phenolic and flavonoid content and enhanced FRAP and DPPH activity of leaf methanolic extracts. Salicylic acid and GA promoted the leaf essential oil content and affected significantly the concentration of limonene, linalool and linalyl acetate.

Effect of asparagine, cysteine, citrulline, and glutamine on in vitro rooting and biochemical constituents in cherry rootstocks

Effects of four amino acids, L-asparagine, L-cysteine, L-citrulline, and L-glutamine in different concentrations (0, 0.5, 1, and 2 mg dm-3) combined with 2 mg dm-3 indole-3-butyric acid, on in vitro rooting and biochemical constituents of cherry rootstocks CAB-6P (Prunus cerasus L.) and Gisela 6 (P. canescens × P. cerasus) were investigated. In CAB-6P, root number and root fresh mass (FM) were maximum at 0.5 mg dm-3 cysteine. All amino acids reduced root length in CAB-6P and root number as well as root FM in Gisela 6. In Gisela 6, 0.5 mg dm-3 asparagine or 2 mg dm-3 glutamine reduced root length. In CAB-6P, 100 % rooting was achieved in the control and with 1 and 2 mg dm-3 cysteine or 1 mg dm−3 citrulline. In Gisela 6, the rooting percentage was maximum (76.92 %) with 0.5 mg dm−3 asparagine. Callus FM in CAB-6P was the greatest at 1 mg dm−3 and in Gisela 6 at 2 mg dm−3 citrulline. Callusing was 100 % in the majority of treatments for CAB-6P and 92.31 % for Gisela 6 with 0.5 or 2 mg dm−3 citrulline. Cysteine, citrulline, and glutamine diminished chlorophyll content in Gisela 6 whereas in CAB-6P all four amino acids hardly affected it. Carotenoid and porphyrin content in CAB-6P was decreased due to asparagine (0.5 or 1 mg dm−3). Porphyrin content in CAB-6P was also reduced by adding 0.5 or 1 mg dm−3 cysteine or 2 mg dm−3 citrulline. In Gisela 6, all amino acids decreased carotenoid and porphyrin content. In CAB-6P, all treatments except 0.5 mg dm−3 glutamine or 2 mg dm−3 asparagine increased leaf sucrose content. In roots, both sucrose and proline content were increased only at 1 mg dm−3 cysteine whereas in leaves only 0.5 mg dm−3 asparagine caused a 3-fold increase in proline content. A decrease in root proline in CAB-6P was observed due to asparagine, citrulline, or glutamine. In Gisela 6, decreased leaf sucrose and proline content was recorded at 2 mg dm−3 cysteine. All amino acids did not alter root sugar content remarkably whereas root proline content was raised by adding 0.5 mg dm−3 glutamine or 1 mg dm−3 cysteine.

Indole-3-butyric acid and myo-inositol impacts on in vitro rooting of the cherry rootstocks CAB-6P and Gisela 6

The present study investigates the effects of indole-3-butyric acid (IBA) alone and in combination with myo-inositol on in vitro rooting and biochemical responses in the cherry rootstocks CAB-6P (Prunus cerasus L.) and Gisela 6 (Prunus cerasus × Prunus canescens). For the CAB-6P rootstock, the best results for root number (6.31), fresh mass (FM), dry mass (DM), and rooting percentage (100 %) were obtained on Murashige and Skoog (MS) medium with 2 mg dm−3 IBA and maximum root length (30.57 mm) was obtained at 1 mg dm−3 IBA. Myo-inositol suppressed the positive effects of IBA on root length. In the Gisela 6 explants, the inclusion of 2 mg dm−3 IBA together with 0.5 mg dm−3 of myo-inositol in the culture medium significantly enhanced root number (9.91) and root FM and DM. The root length was maximum in the combination of the lowest IBA and myo-inositol concentrations (0.5 mg dm−3). The rooting percentage was the greatest (100 %) with the application of 1 mg dm−3 IBA alone. In both explants, the application of IBA alone or in combination with myo-inositol resulted in a lower leaf proline content in comparison with the control (without growth regulators). The maximum leaf chlorophyll content was at 1 mg dm−3 IBA in the CAB-6P whereas at 2 mg dm−3 IBA and 1 mg dm−3 myo-inositol in Gisela 6. Addition of myo-inositol mostly increased sugar content in comparison with control or IBA alone in both rootstocks.

MINERAL STRENGTH, SUCROSE LEVEL AND MANNITOL CONCENTRATION EFFECTS ON CHERRY ROOTSTOCKS MICROPROPAGATION

The aim of the present study was to investigate the effects of two strength media in inorganics (full and half), two sucrose levels (15 and 30 g/l) and four mannitol concentrations (0, 5, 10, 20 g/l) in combination with 1 mg/l indole-3butyric acid (IBA) on the morphogenic and biochemical responses in CAB-6P and Gisela 6 cherry rootstocks. In CAB-6P, root number (7.4) and rooting percentage (83.33%) were maximum in half MS medium supplemented with 5 g/l mannitol and 15 g/l sucrose. Root length was greatest (40.6 mm) with 10 g/l mannitol and 30 g/l sucrose in full MS medium. In Gisela 6, in full MS medium, 20 g/l mannitol + 15 g/l sucrose exhibited the maximum root number (6.88), while 10 g/l mannitol + 30 g/l sucrose gave the greatest root length (50.3 mm). Rooting percentage was highest (92.31%) in half MS + 15 g/l sucrose (mannitolfree) and in 10 g/l mannitol + 15 g/l sucrose (full MS) combination treatments. In CAB-6P, mannitol led to depleted chlorophyll, carotenoid and porphyrin levels in half MS medium for both sucrose levels. Mannitol resulted in elevated leaf and root carbohydrate as well as proline levels irrespective sucrose level and medium strength. In Gisela 6, mannitol + 15 g/l sucrose decreased carotenoid content (full MS) and increased leaf proline content (half MS). In roots, 10 g/l mannitol raised proline (full MS) and carbohydrate content (half MS) in both sucrose levels. Leaf carbohydrate content was higher in half MS medium supplemented with 30 g/l sucrose. In both rootstocks, higher chlorophyll levels were recorded in half MS medium supplemented with 15 g/l sucrose compared to the full MS one or with 30 g/l sucrose. In full MS medium, increase of sucrose concentration led to depleted proline levels in Gisela 6 leaves and CAB-6P roots indicating activation of osmoregulation and osmotic adjustment mechanisms located in leaves for Gisela 6 and in roots for CAB-6P. An efficient root regeneration protocol and biochemical status evaluation of micropropagated cherry rootstocks shoot tips under the combined influence of different strength media, sucrose and mannitol concentrations was established.