Physiological and growth responses of sour cherry (Prunus cerasus L.) plants subjected to short-term salinity stress

The gradual response of CAB-6P sour cherry (Prunus cerasus L.) plants to NaCl-induced salinity stress (60 mM NaCl) was investigated in a short-term hydroponic experiment, based on parameters relating to the growth, water relations, chlorophyll and mineral nutrition. The results showed that CAB-6P plants are very sensitive to salinity stress because their growth and leaf chlorophyll concentration were both affected negatively from the 3rd and 5th day, respectively, after incurring salinity stress. Since root growth was suppressed more severely than shoot growth, the shoot to root ratio was significantly increased under saline conditions. The concentrations of Na in leaves and stem of NaCl-treated plants were much lower than those measured in roots, suggesting Na exclusion mechanism from the shoot. The opposite trend was observed for Cl, indicating Cl inclusion mechanism to leaves. As regards the concentrations of Ca, Mg, P, K, Na, Fe, Zn and Mn, they were not changed in higher salinity conditions, apart from K, concentrations of which in leaves and roots were significantly increased and decreased, respectively (K translocation to leaves). Salinity further reduced K/Na ratio in root and stem as well as leaf water and osmotic potentials, whereas leaves of control and NaCl-treated plants presented similar turgor potential and K/Na ratio. These data add very important information to our knowledge about the physiological events occurring in sour cherry plants after even short-term exposure to salinity

Effect of Lead and Copper on Photosynthetic Apparatus in Citrus (<i>Citrus aurantium</i> L.) Plants. The Role of Antioxidants in Oxidative Damage as a Response to Heavy Metal Stress

Photosynthetic changes and antioxidant activity to oxidative stress were evaluated in sour orange (Citrus aurantium L.) leaves subjected to lead (Pb), copper (Cu) and also Pb + Cu toxicity treatments, in order to elucidate the mechanisms involved in heavy metal tolerance. The simultaneous effect of Pb− and Cu on growth, concentration of malondialdehyde (MDA), hydrogen peroxide (H2O2), chlorophylls, flavonoids, carotenoids, phenolics, chlorophyll fluorescence and photosynthetic parameters were examined in leaves of Citrus aurantium L. plants. Exogenous application of Pb and Cu resulted in an increase in leaf H2O2 and lipid peroxidation (MDA). Toxicity symptoms of both Pb and Cu treated plants were stunted growth and decreased pigments concentration. Furthermore, photosynthetic activity of treated plants exhibited a significant decline. The inhibition of growth in Pb and Cu-treated plants was accompanied by oxidative stress, as indicated by the enhanced lipid peroxidation and the high H2O2 concentration. Furthermore, antioxidants in citrus plants after exposure to high Pb and Cu concentrations were significantly increased compared to control and low Pb and Cu treatments. In conclusion, this study indicates that Pb and Cu promote lipid peroxidation, disrupt membrane integrity, reduces growth and photosynthesis and inhibit mineral nutrition. Considering the potential for adverse human health effects associated with high concentrations of Pb and Cu contained in edible parts of citrus plants the study signals that it is important to conduct further research into the accessibility and uptake of the tested heavy metals in the soil and whether they pose risks to humans

Yield and fruit quality of two late-maturing Valencia orange tree varieties as affected by harvest date

Introduction. Since citrus fruits are non-climacteric, commercial harvest for a given variety can occur over a prolonged period in the same orchard. Delayed citrus harvest has previously been reported to influence fruit quality variables during the current season and to reduce the subsequent year’s yield. The aim of our study was to investigate the effect of harvest date on tree yield and fruit quality of two late-maturing Valencia orange varieties during two successive years. Materials and methods. One hundred 9-year-old Campbell and Lue Gim Gong Valencia orange trees budded on Swingle citrumelo rootstock were used. Fruit sampling included fruit harvest at five monthly intervals (April-August) during 2003, and only one harvest date (20 June) during 2004. Results and discussion. Based on seasonal variation of various fruit quality variables during the five harvests conducted in 2003, the most stable fruit quality variables were fruit weight, number of seeds per fruit, rind thickness, juice content and soluble solids content. In general, both varieties produced fruit with similar internal quality characteristics. However, their mean fruit weight differed in 2004 (Lue Gim Gong had larger fruit than Campbell). Furthermore, the annual and cumulative yields of Lue Gim Gong Valencia orange trees over two years were significantly higher than those of Campbell orange trees. Finally, the yield per tree and fruit quality of both varieties in 2003 and 2004 were not affected significantly by the date of harvest during 2003

Response of Citrus volkameriana (L.) plants to different Mn concentrations under hydroponic conditions.

Plant growth parameters, concentration of proline and carbohydrates in leaves and roots, and total uptake of Mn, Fe, Zn, K, Ca and Mg were determined in Citrus volkameriana (L.) plants after 43 days of growth in nutrient solutions containing 0, 2, 14, 98 or 686 μM Mn. The highest plant growth was observed under 2 μM Mn, while the lowest one under 686 μM Mn. Compared to the treatments 2 and 14 μM Mn, significantly lower concentrations of carbohydrates were found in the leaves and roots of plants grown under 0 or 686 μM, and 0, 98 or 686 μM Mn, respectively. Proline concentration in both leaves and roots was increased by increasing Mn concentration in the nutrient solution. This increase was stronger for the roots (linear correlation) than for the leaves. Mn concentrations in plant tissues and total Mn uptake per plant were progressively increased by increasing Mn concentration in the nutrient solution. However, the total uptake of K, Ca, Mg, Fe and Zn was significantly decreased when the nutrient solution contained 98 or 686 μM Mn, compared to the treatments 0-2 μM Mn. Finally, by increasing Mn concentration in the nutrient solution, plants tended to retain more Ca, Mg and Fe in the roots, and to allow more Zn to be transported to the shoot

Response of Citrus volkameriana (L.) plants to different Mn concentrations under hydroponic conditions.

Plant growth parameters, concentration of proline and carbohydrates in leaves and roots, and total uptake of Mn, Fe, Zn, K, Ca and Mg were determined in Citrus volkameriana (L.) plants after 43 days of growth in nutrient solutions containing 0, 2, 14, 98 or 686 μM Mn. The highest plant growth was observed under 2 μM Mn, while the lowest one under 686 μM Mn. Compared to the treatments 2 and 14 μM Mn, significantly lower concentrations of carbohydrates were found in the leaves and roots of plants grown under 0 or 686 μM, and 0, 98 or 686 μM Mn, respectively. Proline concentration in both leaves and roots was increased by increasing Mn concentration in the nutrient solution. This increase was stronger for the roots (linear correlation) than for the leaves. Mn concentrations in plant tissues and total Mn uptake per plant were progressively increased by increasing Mn concentration in the nutrient solution. However, the total uptake of K, Ca, Mg, Fe and Zn was significantly decreased when the nutrient solution contained 98 or 686 μM Mn, compared to the treatments 0-2 μM Mn. Finally, by increasing Mn concentration in the nutrient solution, plants tended to retain more Ca, Mg and Fe in the roots, and to allow more Zn to be transported to the shoot

Effect of Salinity on Physiological and Biochemical Parameters of Leaves in Three Pomegranate (Punica Granatum L.) Cultivars

Salinity is one of the most important abiotic stresses affecting crop yield. It is important to exploit pomegranates&rsquo; potential against salts because they are considered beneficial plants for human health due to their antioxidants and they are often exposed to severe salinity stress in the field. Three pomegranate cvs. were chosen as model plants for assessing the impact of different salt stress in the cultivation. The aim of this study was to evaluate the physiological and biochemical response of three pomegranate varieties (Punica granatum L.) (Wonderful, Ermioni, and Grenada) under different saline conditions. The plants were grown in a sand/perlite substrate in a 1:1 ratio and, throughout the experiment, were irrigated with a Hoagland nutrient solution, modified to contain four concentrations (0, 25, 50, and 75 mM) of NaCl, KCl, and K2SO4. At the end of the experiment, we measured the (a) concentrations of carotenoids and porphyrin of leaves; (b) phenols and flavonoids contents, and antioxidant capacity of leaves; (c) lipid peroxidation level; (d) leaf water potential; and (e) proline concentration. Ermioni contained the maximum concentration of proline phenols and flavonoids and antioxidant capacity in all salts. Furthermore, reductions in chlorophyll and carotenoid concentration were recorded in all cultivars. Grenada possessed the lowest porphyrin concentration. In conclusion, our results showed that Grenada was the most salt-susceptible cultivar. Salinity treatment triggered the enhancement in lipid peroxidation in the sensitive cultivar, while no change in lipid peroxidation level was observed in the tolerant cultivars. These data provide further support to the hypothesis that a mechanism exists that excludes salinity from the roots of tolerant cultivars, as well as an internal mechanism of tolerance that minimizes the accumulation of lipid peroxides through a higher proline content related to osmoregulation and membrane stabilization

Effect of Salinity on Physiological and Biochemical Parameters of Leaves in Three Pomegranate (<i>Punica Granatum</i> L.) Cultivars

Salinity is one of the most important abiotic stresses affecting crop yield. It is important to exploit pomegranates’ potential against salts because they are considered beneficial plants for human health due to their antioxidants and they are often exposed to severe salinity stress in the field. Three pomegranate cvs. were chosen as model plants for assessing the impact of different salt stress in the cultivation. The aim of this study was to evaluate the physiological and biochemical response of three pomegranate varieties (Punica granatum L.) (Wonderful, Ermioni, and Grenada) under different saline conditions. The plants were grown in a sand/perlite substrate in a 1:1 ratio and, throughout the experiment, were irrigated with a Hoagland nutrient solution, modified to contain four concentrations (0, 25, 50, and 75 mM) of NaCl, KCl, and K2SO4. At the end of the experiment, we measured the (a) concentrations of carotenoids and porphyrin of leaves; (b) phenols and flavonoids contents, and antioxidant capacity of leaves; (c) lipid peroxidation level; (d) leaf water potential; and (e) proline concentration. Ermioni contained the maximum concentration of proline phenols and flavonoids and antioxidant capacity in all salts. Furthermore, reductions in chlorophyll and carotenoid concentration were recorded in all cultivars. Grenada possessed the lowest porphyrin concentration. In conclusion, our results showed that Grenada was the most salt-susceptible cultivar. Salinity treatment triggered the enhancement in lipid peroxidation in the sensitive cultivar, while no change in lipid peroxidation level was observed in the tolerant cultivars. These data provide further support to the hypothesis that a mechanism exists that excludes salinity from the roots of tolerant cultivars, as well as an internal mechanism of tolerance that minimizes the accumulation of lipid peroxides through a higher proline content related to osmoregulation and membrane stabilization

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

Colonization of Greek olive cultivars' root system by arbuscular mycorrhiza fungus: root morphology, growth, and mineral nutrition of olive plants

Rooted leafy cuttings of three Greek olive (Olea europaea L.) cultivars (Koroneiki, Kothreiki and Chondrolia Chalkidikis) were grown for six months in three soil types, in an experimental greenhouse, in order to investigate: i) if their root system was colonized by arbuscular mycorrhiza fungus (AMF) genus and, ii) if genotypic differences concerning growth and mineral nutrition of olive plants existed. Gigaspora sp. colonized the root system of the three cultivars studied, while Glomus sp. colonized only the root system of 'Koroneiki'. Furthermore, in most cases root colonization by AMF differed among cultivars and soil types. The maximum root colonization, in all soils, was found in 'Chondrolia Chalkidikis'. In the three soils studied, the ratio shoot dry weight (SDW)/ root dry weight (RDW) was higher in 'Chondrolia Chalkidikis' than in the other two cultivars. Furthermore, root system morphology of the three olive cultivars was completely different, irrespectively of soil type. Leaf Mn, Fe, Zn, Ca, Mg, K and P concentrations, as well as total per plant nutrient content and nutrient use efficiency, differed among cultivars under the same soil conditions. These differences concerning root morphology, SDW/RDW, as well as nutrient uptake and use efficiency, could be possibly ascribed to the differential AMF colonization by Glomus sp. and Gigaspora sp