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  • Author or Editor: Ioannis Therios x
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Three-month-old rooted olive cuttings (Olea europaea L., cvs. Koroneiki and Kothreiki of ≈20 to 25 cm in height) were grown outdoors for 140 days (from 30 May until 17 Oct.) under ambient conditions in black plastic bags containing 3 kg of soil. Three soils from different parent material (Marl, Gneiss schist., and Peridotite) and with different physicochemical properties were chosen. In all the soils, ‘Kothreiki’ produced significantly greater total plant biomass compared with ‘Koroneiki’. Furthermore, between the two cultivars studied, ‘Kothreiki’ absorbed significantly greater quantity of manganese (Mn), iron (Fe), and zinc (Zn) per plant compared with ‘Koroneiki’. In all the soils, significantly greater concentrations of Mn, Fe, and Zn were recorded in the root system of both cultivars compared with those of leaves and stems. Between the two cultivars studied, ‘Kothreiki’ had greater percentage of the total Mn content distributed in the root system (74% to 80%) than ‘Koroneiki’ (44% to 56%). That high ability of ‘Kothreiki’ to accumulate Mn in its root system could possibly be advantageous in soils with high Mn concentrations and could constitute a detoxification mechanism to olive trees, protecting the above-ground part of the tree from Mn toxicity. Furthermore, greater concentrations of magnesium (Mg) were recorded in the root system of the olive plants than in leaves and stems, whereas potassium (K) and calcium (Ca) concentrations were greater in leaves compared with those of other tissues (roots and stems). The total per plant quantity of Ca, Mg, and K was significantly greater in the cultivar Kothreiki than ‘Koroneiki’ in all the soils tested. On the other hand, ‘Kothreiki’ presented significantly lower use efficiency of Mn in Marl and Gneiss schist soils, and that of Fe and Mg in all soils, so ‘Koroneiki’ could be considered as a Mn- and Fe-efficient olive cultivar, whereas ‘Kothreiki’ was Mn- and Fe-inefficient.

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The chemical and biochemical composition of olives relies on some agronomical factors, one of which is the cultivar. In this study, fruits and leaves of 11 Greek olive cultivars were examined concerning their phenol and oleuropein concentrations. Fruit antioxidant activity was determined as well. The obtained results showed that significant differences existed among cultivars regardless of the tissue or the measured parameter. In general, leaves had higher total phenol and oleuropein concentrations than fruits. Finally, the highest oleuropein concentration in fruits was recorded in ‘Pikrolia Kerkiras’ followed by ‘Romeiki’, ‘Megaritiki’, ‘Kothreiki’, and ‘Kalamon’. These cultivars may constitute the raw material in the industrial production of oleuropein.

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The Nitrate Compensation Points (NCP) of 4 plum clones, Marianna 2624 (Prunus cerasifera Ehrh. × P. munsoniana Wight & Hedr.?), M-17 (P. cerasifera × P. munsoniana?), Myrobalan 3-J (P. cerasifera) and Myrobalan B. (P. cerasifera) were determined following NO 3 depletion from aerated nutrient solutions. Differences among NCP's were statistically significant; however, since the NCP's were low (ca. 5 μm NO 3 ) relative to the [ NO 3 ] of typical agricultural soils, the relevance to NO 3 uptake effectiveness under field conditions remains unresolved. Maximum NO 3 influx took place above 20 μm NO 3 , but 15 hour exposures to higher ambient [ NO 3 ] resulted in higher NCP's. Both decreased influx and increased efflux of NO 3 may have contributed to higher NCP.

Open Access

A field experiment was conducted in a pomegranate (Punica granatum L.) orchard of the well-known cultivars Wonderful and Acco, located in the farm of Aristotle University. The trees were sprayed, every 15 days from flowering (April) to fruit maturation (September), with solutions containing 0, 25, 50, 100 μm Ni, and 100 μm Ni + 100 μm B prepared with Ni(NO3)2·6H2O and boric acid. Leaves and fully ripe fruits were initially sorted into cracked and uncracked ones, then further separated into peel and seeds, sampled, and analyzed. Nickel sprays were effective in controlling fruit splitting as well as Ca and Mg concentration of fruit peels. The correlation between cracking level and Ni concentration in solution was linear and negative. Cracking percentage with 50 μm Ni was lower in ‘Wonderful’, whereas no difference was recorded between the cultivars in the remaining treatments. Leaves had the smallest Ni concentration compared with fruit peel and seeds. Calcium concentration of pomegranate peels was higher than that of control peel at 50 μm Ni in ‘Wonderful’. Concerning ‘Acco’, the treatments 25 μm Ni, 50 μm Ni, and 100 μm Ni + 100 μm B reduced Ca concentration, compared with control. ‘Wonderful’ fruit peel contained more phenolics than ‘Acco’. The treatments 25, 50, and 100 μm Ni increased significantly the flavonoid concentration of fruit peels. The antioxidant capacity ferric-reducing antioxidant potential (FRAP) was linearly increased with Ni concentration in solution in ‘Wonderful’, whereas in ‘Acco’ it decreased at 25 and 50 μm Ni. Our data indicates that improving Ni nutrition of pomegranate can potentially reduce crop loss due to cracking and modified phenol and flavonoid concentration and FRAP value of fruit peel.

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The effect of various commercial calcium (Ca) -containing products applied as preharvest foliar sprays on several fruit quality attributes and nutritional status of the kiwifruit cultivar Tsechelidis for a 2-year period is reported. Foliar application of all Ca products plus boron did not affect mean fruit weight compared with the control. During the first year, the highest flesh firmness was measured after application of the Ca-containing products Acid CaLMg and Calfruit plus Qualyfruit. During the second year, the highest flesh firmness was measured after application of the product Acid CaLMg. The highest ascorbic acid content and total antioxidant power were recorded after application of the product Chelan CaP. Foliar application of Power-Ca resulted in an increase of Ca concentration of leaves compared with the control for the first year. During the second year, all Ca-containing products increased Ca concentration of leaves compared with the control. Foliar application of Calfruit plus Qualyfruit, Chelan CaP, Power Ca, and Acid CaLMg resulted in an increase of Ca concentration of fruits compared with the control. The efficacy of the foliar sprays on some of the tested parameters varied from year to year indicating the influence of other parameters on vine nutrition.

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