Mateusz Wala

Pseudomonas savastanoi pv. phaseolicola, the causal agent of halo blight of bean, is a useful model for studying bacterial adaptation to plant infection. Although its toxins, effectors, population dynamics, and epidemiology have been investigated for decades, these aspects have often been treated separately. This narrative synthesis reinterprets the available literature within a stage-based infection framework encompassing host-surface colonization, establishment of a compatible apoplastic habitat, evasion of host immune responses, multiplication, and spread to another compatible host. Particular attention was given to studies published after the last major review on this pathovar, whereas older studies were retained when they represented primary reports, classical experimental evidence, or information that has not been superseded. The review shows that successful infection is best understood as involving opportunistic entry, rapid transition from an epiphytic to a pathogenic lifestyle, effector-dependent immune suppression, phaseolotoxin-mediated manipulation of host primary metabolism, the exploitation or establishment of hydrated apoplastic conditions, and environmentally driven dissemination. It also distinguishes experimentally supported mechanisms from unresolved or hypothesis-generating areas, including stomatal reopening, micronutrient acquisition, population-level division of labor, alternative hosts, and symptomless reservoirs. The major synthesis emerging from this review is that the infection biology of P. savastanoi pv. phaseolicola cannot be reduced to individual virulence factors because disease development depends on how these factors are coordinated with host-derived resources, immune constraints, and environmental opportunities.

Ranunculus acris L. is a native species widely distributed throughout Europe and is invasive in nonnative areas, causing substantial economic losses in pasture productivity. The present study examined the effects of sodic salinity on the growth and functioning of this species. Salinity stresses the germination process and seedling growth, indicating that the studied species experience serious limitations at 60–90 mmol dm⁻³ NaCl and cannot establish in habitats where salinity is equal to or greater than 150 mmol dm⁻³ NaCl. R. acris is tuned to subsaline habitats characteristic of temperate meadows, as its growth and functioning were the best when the plants were treated with 30 mmol dm⁻³ NaCl. Increasing salinity (60 and 90 mmol dm⁻³ NaCl) hampered growth, leaf morphology and photosynthesis but not mineral nutrition, as Na accumulation seemed to be the most outlined effect of NaCl application. Changes in leaf morphological characteristics coordinated well with Na content in those organs, which indicates that leaf appearance can be easily catchable sign of progressing salinity. Ultimately, progressing salinity reduces the competitiveness of the studied species, shifting its strategy to ruderal behavior, but under subsaline conditions, the strategy of this species seems to be most balanced.

Germination ecology of 10 species from acidic dry grasslands and 10 species from alkaline xerothermic grasslands was studied. The seeds were subjected to different pH, iron (Fe), manganese (Mn) and aluminum (Al) treatments under controlled conditions. Effects of ionic (chlorides) and chelated forms (HBED chelates) of Fe and Mn were also compared. Final germination percentage (FGP) and index of germination velocity (IGV) were calculated. The results indicate that pH and extremely high availability of Al are the major edaphic filters regulating germination-based revegetation, while availability of Fe and Mn is of the secondary importance. Both chelates and ionic forms of Fe and Mn exerted similar effects on the ability of seeds to complete germination. It suggests that both chelates are not hazardous for early ontogenetic stages of plants. Neither group has group-specific adaptations pertaining to germination characteristics in the context of the studied chemical stimuli, which indicates a diversity of germination strategies and individual species-specific reactions to the tested factors.

Centaurea scabiosa L. and C. stoebe Tausch are known to co-exist naturally in two extremely different types of open dry habitats in the temperate zone, alkaline xerothermic grasslands and acidic dry grasslands. However, knowledge about their preferences to edaphic conditions, including soil acidity (pH), and iron (Fe) availability is scarce. Therefore, experimental comparison of soil requirements (acidic Podzol vs alkaline Rendzina) of these species was carried out. The study was designed as a pot experiment and conducted under field conditions. Fe availability was increased by application of Fe-HBED. Reactions of plants to edaphic conditions were determined using growth measurements, leaf morphometric measurements, chlorosis scoring, chlorophyll content and chlorophyll a fluorescence (OJIP) quantification as well as determination of element content (Ca, Mg, Fe, Mn, Zn and Cu). Growth and leaf morphometrical traits of the studied congeneric species were affected similarly by the soil type and differently by the chelate treatment. Increased availability of Fe in Rendzina contrasted the species, as treatment with 25 µmol Fe-HBED kg⁻¹ soil promoted growth only in C. stoebe. Both species turned out to be resistant to Fe-dependent chlorosis which was also reflected in only minor changes in chlorophyll a fluorescence parameters. Both species showed relatively low nutritional demands. Surprisingly, Fe-HBED did not stimulate Fe acquisition in the studied species, nor its translocation along the root:shoot axis. Furthermore, contrary to expectations, C. scabiosa took up less Fe from the acidic than alkaline soil. C. scabiosa not only absorbed more Ca and Zn but also translocated greater amounts of these elements to shoots than C. stoebe. Both species acquired more Mg on Podzol than on Rendzina which suggests adaptation allowing avoidance of aluminum (Al) toxicity on acidic soils. Overall, it seems that C. scabiosa prefers alkaline soils, whilst C. stoebe prefers acidic ones.

The presented study assessed the effect of bovine (BC) and fish (FC) waste-derived collagen, poly(hexamethylenebiguanide) hydrochloride (PHMB) and waste dolomite on the emergence of seedlings, growth and development of pea (Pisum sativum L. ‘Lasso’) plants. The seed coating method was used to apply the binding agents. Some of the studied agents were showed to significantly affect the index of emergence velocity (IEV) and of emergence synchrony (IES), but not the final emergence percentage (FEP). The results showed that treatment of the pea seeds with BC, FC and PHMB had a slightly positive effect on plant growth, whereas negative effects of dolomite were observed, i.e., detrimental differences in morphological traits of stipules. Moreover, BC, FC and PHMB improved maximal efficiency of PSII (F_V/F_M) and did not negatively influence chlorophyll content. Analyses demonstrated positive effects of FC and PHMB and negative ones of BC and dolomite on elemental composition of roots and shoots of the studied plant species. We suggest that the FC and PHMB can be used as promising agents for improvement of plant growth, whereas usage of BC and dolomite should be limited.