Links between germination, DNA replication and p-tubulin accumulation were studied with cabbage (Brassica oleracea L) seeds, by using flow cytometric analysis of nuclear DNA content and immunodetection of p-tubulin levels The seeds were incubated in water or 0 1-500 ITIM hydroxyurea solutions Radicle tips isolated from dry cabbage seeds revealed most 2C (G o or G 1 stage) and some 4C (G 2 stage) signals of nuclear DNA contents and a constitutive level of (3-tubuhn 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 (3-tubuhn 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 (3-tubulin was not affected by hydroxyurea Thus, it can be deduced that both DNA replication and p-tubuhn accumulation are two parallel and independent cell cycle events during seed germination

The effects of Asahi SL (sodium ortho and para-nitro phenolate, sodium 5 nitro guaiacolate) sprays on China aster plant height, seed yield and some metabolic events were investigated. The plants were sprayed with Asahi SL, in concentration of 0, 0.1, 0.2 or 0.4 %, three times before or during flowering, and six times before and during this stage. It was found that Asahi SL applied three times during flowering brought about an increase in the seed yield, germination and metabolic activity and did not modify vegetative growth of plants. The chemical used earlier, before flowering, had detrimental effect on seed yield and quality, although it stimulated vegetative growth. The positive effect of Asahi SL was more prominent in weather conditions unfavourable for seed production.

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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.

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 , 10and 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 growthinhibiting 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).

This work was carried out under the multiannual program "Actions to improve the competitiveness and innovation of the horticultural sector, taking into account food quality and safety and environmental protection", financed by the Ministry of Agriculture and Rural Development in Poland (2014-2018).A b s t r a c t. The most significant problem, in ecological vegetable seed production, is low, capacity which is mainly caused by high rates of seed infection with fungi and a shortage of effective biological agents to eliminate pathogens. Therefore, proecological methods of seed quality enhancement are being researched, with the aim of increasing the profitability of seed production by improving the seed sowing value. The aim of the work was to evaluate the effectiveness of pulsed radio frequency on the seed quality of selected vegetable cultivars. The results obtained from research conducted in laboratory, greenhouse and field conditions indicate the protective effect of pulsed radio frequency treatment of seeds by a reduction in the incidence of beetroot, lettuce and garden dill seed-borne fungi, and an improvement in their health status and germination capacity. The presowing application of pulsed radio frequency resulted in a 60-80% reduction of seed infestation with fungi, depending on the plant species. This treatment improved the dynamics of seed germination, plant emergence, growth, and increased the chlorophyll content and gas exchange in leaves. The most beneficial results were obtained in beetroot, in which the problem of seed production is associated with a high rate of seed infestation with mycoflora and the presence of germination inhibitors in the seed coat. The results indicate the high efficiency of the applied pulsed radio frequency and its usefulness in ecological and integrated seed production. K e y w o r d s: seeds, lettuce, beetroot, garden dill, pulsed radio frequency, health status

The aim of the study was to shorten the period of breaking dormancy in apple seeds and to improve the growth of the seedlings of 'Gold Milenium', 'Ligol' and 'Szampion'. The whole seeds were removed from fruits directly after the harvest and were subjected to stratification (3 °C for 90 days in darkness) in distilled water or an aqueous solutions of 500 mM salicylic acid (SA), 10 -3 M jasmonic acid (JA), gibberellin A3 (GA3) and 6-benzylaminopurine (BAP) at 250 mg·dm -3 and 100 mg·dm -3 , respectively. Growth regulators were applied separately or in a mixture containing SA, JA, GA3 and BAP. The germinability and seed germination rate, seedlings growth, chlorophyll content index and the maximum quantum efficiency of Photosystem II (Fv/Fm) were investigated. The obtained results revealed that stratification in water positively affected the dormancy removal in 'Gold Milenium', 'Ligol' and 'Szampion' seeds. Application of SA, GA3, BAP, JA during seed stratification additionally stimulated the seeds' germination rate as well as the growth of seedlings, index of chlorophyll content and maximum PSII efficiency (Fv/Fm). The most pronounced results were obtained after the seed stratification in GA3 alone or in a mixture containing SA, GA3, BAP and JA. Due to such a treatment, the germination of 'Ligol' seeds increased by 40% and they germinated faster in comparison to the control seeds. Such treatments also promoted the growth of seedlings, chlorophyll content and maximum quantum efficiency of Photosystem II (Fv/Fm). The present study indicates that the application of GA3 or the mixture of SA, GA3, BAP and JA during the stratification of seeds is an effective method to increase and accelerate the germination of seeds and juvenile seedlings' growth in order to shorten the apple breeding cycle. Further studies are needed to optimize the appropriate concentration of growth regulators applied simultaneously during seeds stratification.

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.