Investigating the improvement of germination indices of Cynara scolymus L. seed by bacterial strains of Pseudomonas sp. R27N7 and Staphylococcus sp. R38N2 along with extracted humic and fulvic acids from biochar of Oriental plane tree

The aim of this study was to investigate the effect of artichoke (Cynara scolymus L.) seeds priming with plant growth-promoting rhizobacteria and extracted humic substances from biochar of Oriental plane (Platanus orientalis) tree on their seeds germination and seedling growth indices. For this purpose, in-vitro culture was performed in the form of factorial in a completely randomized design with four replications, totally in 36 experimental units, in the laboratory of soil science department, University of Zabul, in spring 2021. The first factor (humic substances) was in three levels including: seed priming with distilled water (control), fulvic acid and humic acid. The second factor (plant growth-promoting rhizobacteria) was in three levels including: seed priming with physiological serum (control), strains of Pseudomonas sp. R27N7 and Staphylococcus sp. R38N2. The results showed that R27N7 and R38N2 bacterial strains reduced the mean germination time by 10.93% and 11.23%, respectively, compared to the control. The effect of fulvic acid treatment on variation of measured indices was not significant compared to control. But, humic acid treatment increased indices of Seedling height by 90.33%, seedling dry weight by 90.70%, germination percentage by 61.32%, germination rate by 62.50%, mean daily germination by 60.19% and vigor index I and II by 2.76 times compared to the control. According to the results of this study, artichoke seeds priming with both of the plant growth promoting rhizobacteria strains can reduce mean germination time of seed. Also, seeds priming with humic acid can improve dry weight of seedling and most of seed germination indices. It seems that the improvement of these indices is mostly influenced by the plant growth hormone-like properties of humic acid and also plant growth promoting properties of both bacterial strains, especially their ability to produce of indole-3-acetic acid.