The aim of this study was to compare the effects of foliar fertilization with a nitrogen (N) fertilizer containing nanoparticles (nN) with those of foliar fertilization with urea on the characteristics of pomegranate fruits cv. Ardestani. The experiment was carried out using a completely randomized block design with five treatments and four replications (trees) per treatment during two consecutive years, 2014 and 2015. Two foliar applications of nN (0.25 and 0.50 g N/L, equivalent to ≈1.3 and 2.7 g N/tree or 0.9 and 1.8 kg N/ha; nN1 and nN2, respectively) and urea (4.6 and 9.2 g N/L, equivalent to ≈24.4 and 48.8 g N/tree or 16.3 and 32.5 kg N/ha; U1 and U2, respectively) were applied at full bloom and 1 month later, and trees not treated with any N fertilizer were used as a control. Results show that foliar N fertilization increased fruit yield (by 17% to 44%) and number of fruits per tree (by 15% to 38%). The highest fruit yields (17.8 and 21.9 kg/tree) and number of fruits per tree (62.8 and 70.1/tree) were obtained with the treatment nN2 (1.8 kg N/ha), whereas the lowest fruit yields (12.4 and 16.2 kg/tree) and number of fruits per tree (45.5 and 55.3/tree) were recorded in the control trees. The treatments U1 and nN2 increased fruit length (the latter only in the second season), whereas the treatment U1 increased average fruit weight (10% to 11%). The treatment nN2 increased aril juice and total soluble solids (TSS) in both seasons and titratable acidity (TA) only in the first one, whereas the treatment U1 increased TSS in both seasons and aril juice and TA in the second season. Treatments nN2 and U1 also increased total sugars and decreased total anthocyanins. On the other hand, fruit diameter, fruit cracking, peel thickness, aril content, weight of 100 arils, juice pH, maturity index, antioxidant activity, and total phenolic compounds were unaffected by N fertilization. Nitrogen fertilization increased the leaf concentration of N, whereas the leaf concentrations of P, K, Mn, and Zn were unaffected. Results indicate that pomegranate fruit yield was improved similarly with two applications (at full bloom and one month later) of nN fertilizer at a rate of 1.8 kg N/ha and with two applications of urea at a rate of 16.3 kg N/ha. Furthermore, fruit quality was improved more with the nN fertilizer at a rate of 1.8 kg N/ha than with two applications of urea at a rate of 16.3 kg N/ha.

Early season foliar fertilization with different nutrients is a promising tool in pomegranate grown in poor, high pH soils. The effects of foliar fertilization with FeSO₄ and the synthetic chelate Fe(III)-EDDHA (Fe(III)-ethylendiaminedi(o-hydroxyphenylacetate)) on fruit yield and physicochemical characteristics were assessed in a two-season field trial. Fertilizers were sprayed at full bloom and one month later, using Fe concentrations of 1.3 and 2.6 mM for FeSO₄ and 1.1 and 2.1 mM for the Fe-chelate. Both doses of FeSO₄ and the higher chelate dose increased leaf Fe concentrations and fruit yield, with the best results being observed with 2.6 mM FeSO₄ (20–31% increases in yield). On the other hand, leaf N, P, K, Ca, and Mn concentrations were not affected by foliar Fe fertilization. The only treatment that increased the number of fruits per tree, aril juice content and juice total soluble solids and decreased juice total acidity in both seasons was 2.6 mM FeSO₄. Both FeSO₄ doses caused consistent increases in the maturity index and total sugars in juice, along with minor decreases in juice total phenolic compounds. The antioxidant activity in juice was slightly decreased by 2.6 mM FeSO₄. In conclusion, early season foliar Fe fertilization had positive effects on pomegranate yield and quality, with FeSO₄ being better than Fe(III)-EDDHA.

Rosa canina is one of the most popular rose species which is widely used as the rootstock for the propagation of rose cultivars. The purpose of the present study is to improve the in vitro propagation efficiency of this valuable plant species using various growth stimulants in a proliferation medium. In this study, in vitro-derived axillary buds of R. canina were inoculated in Vander Salm (VS) medium supplemented with varying levels of organic or inorganic elicitors including casein hydrolysate (200, 400, and 600 mg/l), glutamic acid (2, 4, 8, and 12 mg/l), proline (500, 1000, 1500, and 2000 mg/l), and silver nitrate (25, 50, 75, and 100 mg/l), separately. Benzyl amino purine (BAP) as well as naphthalin acetic acid (NAA) were added to all media at a constant rate to promote shoot proliferation. The results indicated that the supplementation of casein hydrolysate to the VS medium markedly stimulated shoot regeneration by 173% in comparison to control. Shoot proliferation was also positively influenced by glutamic acid at all levels, however, at a lesser extent compared to casein hydrolysate. Silver nitrate at 100 mg/l induced the longest shoots (2.52 ± 0.248 cm) and maximum leaf number (8.90 ± 0.276) among all treatments. Although it did not encourage efficient shoot regeneration, the highest quality shoots with maximum growth vigor were observed in this treatment. In this study, the promising role of casein hydrolysate in combination with plant growth regulators has been emphasized for the improved efficiency of R. canina regeneration protocol. Moreover, the addition of silver nitrate to the culture medium seems vital for enhancing the quality of regenerated shoots. The results of this study could be beneficial either for the further pharmaceutical or biochemical investigations of R. canina or commercial purposes for mass propagation of this specimen.