Τhe production of fresh fruit as well as olive orchards is increasing around the world, in order to meet the global demand for both fruits and olive products. This results in the spread and establishment of fruit and olive tree cultivation in areas where they were not found before, for example, plains and lowlands prone to waterlogging. Climate change is having a significant impact on the natural environment. Agricultural open-field crops have less growth and yield under these harsh weather conditions. Nowadays, unpredictable rainfall more often exposes field crops to waterlogging on a regular basis. This is a very stressful factor which can cause a reduction in yield and even total crop elimination. In this review, the morphological and physiological parameters affected by waterlogging are developed in order to understand better how olive and other fruit crops respond to waterlogging conditions and how this affects their development and productivity. Having a better understanding of these mechanisms can help us design strategies and approaches to increase fruit crop resistance to waterlogging stress.

Magnesium is an essential nutrient for the growth and development of plants. Its deficiency is becoming a growing concern in many citrus orchards worldwide, adversely affecting numerous functions in plants and limiting their productivity and quality. Three-year-old orange (Citrus sinensis cv. Newhall) plants grafted on Swingle citrumelo (C. paradisi Macf. × Poncirus trifoliata L.) rootstock were irrigated for 63 days with nutrient solutions containing 0, 12, 24, 48, 96, and 192 mg Mg L⁻¹. Thereafter, Mg deficiency-induced changes were investigated in leaf chlorophyll concentration and fluorescence, and in proline and carbohydrate concentration in leaves and roots, as well as in the nutritional status of leaves, stems, and roots. Magnesium concentration in the nutrient solution was positively correlated with the concentration of Mg (leaves, stems, roots), Ca (rootstock’s stem), K (roots), and Fe (leaves, rootstock’s stem), as well as with the total Mg absorption. However, Mg concentration in the nutrient solution was negatively correlated with the concentration of Mn (rootstock’s stem, roots), Ca (leaves, scion’s stems, roots), and Fe (roots), as well as with the total absorption of Mn, Fe, P, K, and Ca. The lower values of the chlorophyll fluorescence parameters were observed by the effect of the highest concentration of Mg. As far as leaf chlorophyll concentration and carbohydrate and proline content of leaves and roots, they were not affected by the Mg treatments. Concluding, this research highlights the significance of Mg management in citrus farming, offering insights into increasing Mg concentrations, understanding root mechanisms in Mg absorption, and suggesting the benefits of fertilization to address Mg deficiency. It emphasizes the importance of careful Mg fertilizer dosages, considering other nutrient interactions, and provides valuable guidance for optimizing Mg nutrition and overall nutrient management in sweet orange trees.

The aim of this research was to study the effect of high boron (B) irrigation water on the appearance of B toxicity symptoms and on the seasonal variation of nutrients in leaves and fruits of two table cultivars of olive (Olea europaea L.). The cultivars ‘Chondrolia Chalkidikis’ and ‘Amfissis’ located in the same orchard and irrigated with water having an average B concentration of 3.6 mg l^–1 were studied. Leaf samples from the current and the previous year non-bearing shoots were collected at 15 or 30 d intervals for a period of 15 months (24 months for B samples). All the leaf and fruit samples were analysed for N, P, K, Ca, Mg, B, Fe, Mn, and Zn. Inflorescence samples were collected at full bloom, while fruit samples were collected 30, 60, 90 and 120 d after full bloom. Also, samples of irrigation water and soil were collected during the experiment and analysed. The results indicated that olive is a species relatively tolerant to excess soil B and no visual symptoms of B toxicity were observed on leaves. Furthermore, B concentration of leaves was at an adequate level, or slightly above it. The two cultivars followed a similar pattern of the fluctuation of B concentration during summer. The maximum B concentration in leaves was 175 mg kg^–1 dry matter in ‘Chondrolia Chalkidikis’ leaves and about 70 mg kg^–1 dry matter in ‘Amfissis’ leaves. The nutritional status of trees for K, Ca, Mg and Fe was found to be sufficient, while Mn was deficient. Nitrogen and P were at the sufficiency level in ‘Chondrolia Chalkidikis’, but at the marginal level in ‘Amfissis’. Generally, B concentration of flowers was higher than that in the leaves, for the same sampling time. ‘Chondrolia Chalkidikis’ presented significantly higher B concentration in fruit than ‘Amfissis’, during the harvesting period.

The effect of radiation quality (350 – 740 nm) and darkness (D) on in vitro rooting, and chemical composition of the peach rootstock GF 677 was studied. Shoot explants were exposed for four weeks to cool white (control) (W), red (R), blue (B), green (G) or yellow (Y) radiation from fluorescent tubes. Some of the explants were kept in D during the rooting stage and others were maintained only for the first 2- or 4-d under R, B, G, Y or D, and subsequently were transferred to W. W was the most effective radiation source for adventitious root formation of GF 677 explants. Rooting was inhibited in those plants that remained in continuous D, and R reduced root growth in all treatments. The 2- or 4-d exposure to D, Y or B followed by W helped adventitious root development similarly as did W. G significantly increased Fe concentration in roots.