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Imbalanced Ca/Mg and excess Ni (due to serpentine stress) are limiting factors for plant productivity. The purpose of this study was to investigate if growth, nutrient uptake, PSII activity, photosynthesis and antioxidant activity of pomegranate (Punica granatum L., cv. Granada) plants were affected by serpentine stress. Pomegranate plants were grown in soil substrates from parent material marl (control), serpentine and serpentinized peridotite. Plant height, leaf, stem, root and total plant dry weight, as well as foliar N, P, K, Ca, Zn, Cu, chlorophyll content, fluorescence parameters, photosynthetic rate, and internal water use efficiency (WUEi) were significantly lower for the plants grown in the serpentinized peridotite soil. In contrast, higher ferric reducing antioxidant power (FRAP), total phenolics and total flavonoid content (TFC) levels were found in the serpentinized peridotite soil. The insignificant differences between the marl and serpentine soils in plant growth, PSII activity, photosynthesis and nutrient uptake indicated that P. granatum could tolerate a mild (not with extremely high Ni) serpentine stress. However, P. granatum could not tolerate stress showing excess Mg and imbalanced Ca/Mg, as found for the serpentinized soil of our study. • Soils from marl, serpentine and serpentinized peridotite were used as substrates. • Most foliar nutrients were significantly lower in the serpentinized peridotite soil. • Photosynthesis was significantly lower in the serpentinized peridotite soil. • Chlorophyll and PSII activity were significantly lower in the serpentinized soil. • Increased levels of phenols, TFC and FRAP were found in the serpentinized soil. [ABSTRACT FROM AUTHOR]

A greenhouse experiment was conducted, in order to study the effect of nitrogen (N) form (NO 3 − , NH 4 + , urea, NH 4 + + NO 3 − ) and concentration (1, 8 and 16 mM) on growth, mineral nutrition and photosynthetic performance of olive plants ( Olea europaea L., cv. ‘Kalamon’). Our data indicate that when plants at high supply (16 mM) received urea as N source better growth performance was recorded, compared to the cases olive plants received other N forms; however, at low to medium N supply (1 or 8 mM) better plant growth performance observed when they were fertilized with NO 3 − –N. Total N uptake at 16 mM was significantly lower when plants received NO 3 − –N, in comparison to the other N forms. NO 3 − form at 16 mM resulted in lower total uptake of P, Fe, Mn and Zn, compared to the other treatments. On the other hand, NH 4 + -N at high N supply (16 mM) resulted in lower total uptake of Ca and Mg. However, significantly higher K uptake was found when plants were treated with NH 4 + , at high N rate (16 mM). High N supply in the form of NH 4 + -N significantly inhibited net photosynthetic rate (A), although the chlorophyll fluorescence (as an indicator of the function of PSII) did not significantly differ among the N treatments. In conclusion, urea-N proved to be the most appropriate N form for the mineral nutrition of the olive cultivar ‘Kalamon’; thus, it should be preferred as a source of N in olive groves receiving high N fertilizations. [ABSTRACT FROM AUTHOR]

• Olive plants were fertilized with manures or a controlled release fertilizer (CRF). • The highest biomass, macronutrient content and PSII activity were found in the CRF. • Significantly lower photosynthetic rate and stomata opening were recorded in the CRF. • The lowest foliar P, K, Mg, Zn and Cu concentrations were found in the CRF. • The higher macronutrient accumulation in the CRF was owed to the higher biomass. Organic fertilization has been proposed as an alternative method, in the frame of sustainable agriculture, to enhance soil fertility and satisfy the nutritional needs of crops, without the input of chemical fertilizers. A six-month pot experiment, with 3 soil amendments, used as organic fertilizers (cow manure-CM, goat manure-GM, and their mixture, i.e. CM + GM) and a controlled release fertilizer (CRF) was conducted, in order to investigate if the growth, nutrient uptake, photosystem II (PSII) activity, photosynthetic rate and total sugars of Olea europaea L. (cv. 'Koroneiki') plants were influenced by the kind of fertilization. The highest plant biomass, macronutrient content and PSII activity were found in the CRF treatment. In contrast, significantly lower photosynthetic and transpiration rates were recorded in the CRF due to the lower stomatal conductance. Translocated sugars were higher in the CM + GM treatment, while total sugar concentration did not significantly differ among the treatments. Despite the highest content of all macronutrients, Fe and Mn recorded in the CRF, the lowest foliar P, K, Mg, Zn and Cu concentrations revealed that the higher nutrient accumulation, compared to the organic treatments, should be ascribed to the higher plant biomass, rather than to higher nutrient uptake. From the above data, it is clear that the kind of organic/inorganic fertilization significantly influenced soil organic C content, fertility, growth, nutrient uptake and the physiology of olive plants. Thus, the kind of manure(s) used to enhance soil fertility and support crop production should be seriously taken into consideration by the olive growers before its/their use. [ABSTRACT FROM AUTHOR]

• Pomegranate cultivar (cv.) 'Grenada' was the most susceptible under all saline conditions. • Pomegranate cvs. 'Wonderful' and 'Ermioni' may be cultivated under saline conditions. • Concentrations of Ca and Mg in leaves significantly reduced under KCl and K 2 SO 4 salts. • The highest concentrations of KCl and K 2 SO 4 (75 mM) decreased the chlorophyll concentration. The present investigation assesses the behavior of three pomegranate cultivars (Punica granatum L.) ('Wonderful', 'Ermioni' and 'Grenada') under increased concentrations of three salts (NaCl, KCl and K 2 SO 4) after 150 days of growth in vivo conditions. The aim of this research was to study the nutrient accumulation and distribution in leaves and roots and its effects on total chlorophyll (a + b), carotenoids, photosynthetic rate and stomatal conductance of leaves. In general, high salt supply of KCl and K 2 SO 4 led to significant decline in Ca and Mg concentration in leaves in all cultivars. 'Grenada' found with the highest concentration of Mn in leaves under all salt treatments. Regarding the roots, 'Wonderful' had the highest Mg concentration at 25, 50 and 75 mM of KCl and K 2 SO 4 , while 'Ermioni' had the maximum Ca concentration in roots. Chlorophyll concentration was reduced by the effect of KCl and K 2 SO 4 salts in all cultivars. Furthermore, K 2 SO 4 salt significantly reduced carotenoid concentration in leaves in all cultivars, especially 'Wonderful' showed 63.36 % reduction. 'Grenada' had the lowest photosynthetic rate and K 2 SO 4 salt exerted a significant effect in all cultivars. Regarding stomatal conductance, 'Ermioni' had the highest values with KCl and K 2 SO 4 salt treatments, while 'Grenada' was the most affected cultivar by all salts and at all concentrations. Our findings show the considerable potential of exploiting saline soils to obtain pomegranate plants with higher level of salt tolerance. Furthermore, our results suggest that 'Wonderful' and 'Ermioni' pomegranate cultivars may be cultivated also under marginal saline conditions. [ABSTRACT FROM AUTHOR]