Although the application of chemical fertilizers to crops promotes plant growth and yield, their continuous use affects soil heath and creates environmental pollution. On the other hand, plant biostimulants improve nutrients absorption, plant growth, yield and produce quality and are environment-friendly. Therefore, an experiment was conducted during 2021-22 to evaluate the effect of some biostimulants on the performance of the apple cv. Anna, planted in a sandy loam soil at Marsa Matruh governorate, Egypt. Ninety trees were randomly selected and sprayed with 4 or 6% moringa leaf extract (MLE), 0.3 or 0.4% seaweed extract (SWE), 1000 or 2000 mg L⁻¹ Fulvic acid (FA), 4% MLE + 0.3% SWE + 1000 mg L⁻¹ FA (combination 1), or 6% MLE + 0.4% SWE + 2000 mg L⁻¹ FA (combination 2) before flowering, during full bloom and one month later and compared with a control (untreated trees). The results demonstrated that spraying MLE, SWE or FA or their combinations positively improved the vegetative growth, fruit set %, fruit yield and fruit physical and chemical characteristics as well as leaf nutritional status. The positive effect of MLE, SWE and FA was increased in parallel to an increase in the used concentration of each one of them. The highest increments in the measured parameters were accompanied by the application of combination 2 over the other treatments.

Links between germination, DNA replication and β-tubulin accumulation were studied with cabbage (Brassica oleraceaL.) seeds, by using flow cytometric analysis of nuclear DNA content and immunodetection of β-tubulin levels. The seeds were incubated in water or 0.1–500 mM hydroxyurea solutions. Radicle tips isolated from dry cabbage seeds revealed most 2C (G_oor G₁stage) and some 4C (G₂stage) signals of nuclear DNA contents and a constitutive level of β-tubulin. The onset of DNA replication in the radicle tip was observed between 12 and 24 h of imbibition in water and was preceded by an increase of β-tubulin levels. Incubation of the seeds in 1 mM hydroxyurea retarded DNA replication, whereas an arrest of DNA replication occurred upon incubation in 10 mM hydroxyurea or higher concentrations. The arrest of DNA replication and cell division did not block radicle protrusion and allowed some extension of the radicle. This demonstrated that DNA replication is not a prerequisite for radicle protrusion and initial extension. However, further seedling development, including root growth and root hair development, was dependent on DNA replication. Accumulation of β-tubulin was not affected by hydroxyurea. Thus, it can be deduced that both DNA replication and β-tubulin accumulation are two parallel and independent cell cycle events during seed germination.

Weather fluctuations significantly affect the growth and production of orchard crops such as mango, leading to a substantial decrease in tree growth, flowering rate, yield, and fruit quality. One of these weather factors is drought, which negatively influences multiple physiological processes in plants. It increases the transpiration rate and decreases the cell turgidity, stomatal regulation, osmoregulation, water utilization efficiency, and the development of the deep root system; consequently, it decreases the final production and fruit quality. Therefore, the present study was performed in the 2022–2023 seasons to study the role of the spraying of Selenium (Se), Titanium (Ti), and Silicon (Si) nanoparticles on the growth parameters, yielding, fruit physical and chemical characteristics, and leaf mineral composition of mango cv. Keitt. Mango trees were sprayed during the vegetative season 2022–2023 three times, starting in April with three weeks intervals, by 5, 10, and 20 mg/L Se; 40, 60, and 80 mg/L Ti; and 50, 100, and 150 mg/L Si. The results showed that the extern spray of nanoparticles from these micronutrients improved the growth attributes, yielding and fruit quality of mango trees by reducing the effect of undesirable stressful conditions. The results also indicated that the extern implementation of 150 mg/L Si, 60 mg/L Ti and 20 mg/L Se gave the best increments in the shoot number, length, thickness, leaf area, and leaf chlorophyll contrasted to the else sprayed treatments. Besides, they also improved the fruit set percentages, fruit yields, fruit physical and chemical characteristics and nutritional status of mango trees in both tested seasons.

The objective of this study was to analyze the mechanism of some physiological processes accompanying acquisition of sunflower (Helianthus annuus L.) chilling resistance due to seeds hydropriming in the presence of salicylic acid, jasmonic acid, 24-epibrassinolide followed exposition of seeds to short-term heat shock treatment. The seeds were hydroprimed at 25 °C in limited amounts of water or solution of salicylic or jasmonic acid at 10⁻², 10⁻³ and 10⁻⁴ M concentration, 24-epibrassinolide at 10⁻⁶, 10⁻⁸ and 10⁻¹⁰ M concentration. The seeds were incubated for 2 days, subjected to short-term heat shock (45 °C, 2 h) and chilled for 21 days at 0 °C. Sunflower chilling susceptibility and physiological responses were evaluated according to the inhibition of radicle growth, the inhibition of the number of lateral roots formation, the activity of catalase and changes in soluble carbohydrates in seedlings developing for 72 h at 25 °C. Hydropriming and short-term heat shock application explicitly reduced inhibition of roots as well as lateral roots development by allowing the germinating seeds to recover from the growth-inhibiting effects of chilling. Seeds hydropriming in solutions containing salicylic acid, jasmonic acid and 24-epibrassinolide followed heat shock treatment additionally promoted the activity of catalase and sugars metabolism, which stimulated seedlings development and alleviated the decrease of F _v/F _m caused by chilling conditions. These beneficial effects contributed to increased resistance of sunflower seedlings to chilling stress. The present study demonstrated that the most profitable effect on reducing negative effect of chilling may be achieved by short-term heat shock applied during hydropriming in water supplemented with 24-epiBL (10⁻⁸ and 10⁻¹⁰ M) or salicylic acid (10⁻³ and 10⁻⁴ M).

The aim of this study was to develop the method for increasing resistance of sunflower seedlings ‘Wielkopolski’ to chilling. Seeds were conditioned at 25 °C for 2 days in water to 15, 20 and 25 % moisture content or in salicylic or jasmonic acid in concentration of 10⁻²; 10⁻³ and 10⁻⁴ M or brassinolide in concentration of 10⁻⁶; 10⁻⁸ and 10⁻¹⁰–15 % moisture content. After 2 days of incubation the conditioned seeds were heat shocked at 45 °C for 0, 30, 60, 120 and 240 min and 5 mm seedlings were exposed to chilling at 0 °C for 21 days. The effectiveness of the methods was assessed by evaluation of roots growth in Phytotoxkit Microbiotest, changes in the activity of dehydrogenases, the integrity of the cytoplasmic membrane and formation of polysomes after seedling were returned to 25 °C for 72 h. Seeds were conditioned at 25 °C for 2 days in water to 15 % moisture content and then heat shocked at 45 °C for 2 h decreased chilling injury of seedlings expressed by subsequent growth of the roots, electrolyte leakage, dehydrogenases activity and polysomes formation. Application of heat shock of 45 °C for 2 h during seed conditioning additionally provided seedling protection against subsequent chilling conditions. Brasinolide, salicylic acid or jasmonic acid applied during seeds conditioning exhibited further beneficial effect on seedling resistance to chilling. The most pronounced effect was obtained due to seed conditioning to 15 % moisture content in solutions of brassinolide in concentration of 10⁻⁸ M. After 2 days of imbibition treated in this way seeds were exposed to heat shock at 45 °C for 2 h. The role of physiological events in improvement of sunflower chilling tolerance are discussed.