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ABSTRACTMicrobial soil additives and plant biostimulants contain substances and microorganisms that can enhance stress tolerance in plants and increase the yield and quality of the crop. The interest in such inputs for sustainable and agroecological farming systems has led to the development of a range of products. The aim of the study was to determine the effects of some microbial soil additives (MSADs), plant growth promoters (PGPs) and biological control agents (BCAs) on photosynthetic efficiency, canopy vegetation indices and yield of common buckwheat (Fagopyrum esculentumMoench), an under-utilised nutraceutical crop. The study showed that soaking the seeds in the BCAs Pythium oligandrumand Bacillus subtilis, on their own, had significant effects on the yield of the buckwheat. Increases in chlorophyll afluorescence indices were observed in plants grown from seeds soaked in a solution containing P. oligandrum(ET0/RC) and also in soil treated with the MSAD UG Max (ABS/RC, TR0/RC). Treatment with either of the two MSADs also increased the normalised differential vegetation index (NDVI). Soaking the seeds in PGPs combined with BCAs affected only the chlorophyll afluorescence parameters, whereas the combined treatment of spraying the plants with PGPs and treating the soil with MSADs affected not only the chlorophyll afluorescence parameters (FV/FM, ET0/RC, DI0/RC), but also indicated a tendency for a decrease in the leaf area index (LAI) (p= 0.058) and the NDVI (p= 0.186). The correlations between grain yield, chlorophyll afluorescence parameters and vegetation indices of the canopy were discussed.

The total soluble sugar content and antioxidant enzyme activities were studied for the first time during axillary shoot formation in Magnolia× ‘Spectrum’ in vitro in response to BAP (0.3 mg l−1), different levels of gibberellic acid (GA3; 0.0, 0.1, 0.5, 1.0 mg l−1), sucrose (20 and 30 g l−1) and nitrogen salts (KNO3/NH4NO3; 100/100% and 75/50% relative to MS medium). Among various GA3and sucrose/nitrogen salts ratios, the most effective axillary multiplication (5.9 shoots/explant) and leaf formation (25.7 leaves per multiplied clumps) were obtained after addition of GA3at 0.1 mg l−1to a BAP medium containing 20 g l−1sucrose and reduced levels of nitrogen salts (75% KNO3and 50% NH4NO3). The addition of GA3to the BAP medium enhanced shoot formation by 36% and leaf formation by 27%. The highest shoot formation capacity of M.× ‘Spectrum’ in vitro coincided with enhanced levels of soluble sugar and peroxidase (POD) activity. Increasing GA3concentration from 0.1 to 1.0 mg l−1in the above medium resulted in inhibition of shoot and leaf formation and a decrease in the soluble sugar content. The influence of GA3on the activities of catalase (CAT) and POD depended on its concentration and the levels of sucrose and nitrogen salts in the medium. The highest increase in CAT and POD activities, that coincided with the enhanced shoot formation capacity of M.× ‘Spectrum’ in vitro, was observed after addition of GA3to the medium containing high levels of sucrose and nitrogen salts.