The main topic of this study is the bioremediation potential of the common duckweed, Lemna minor L., and selected rhizospheric bacterial strains in removing phenol from aqueous environments at extremely high initial phenol concentrations. To that end, fluorescence microscopy, MIC tests, biofilm formation, the phenol removal test (4-AAP method), the Salkowski essay, and studies of multiplication rates of sterile and inoculated duckweed in MS medium with phenol (200, 500, 750, and 1000 mg L⁻¹) were conducted. Out of seven bacterial strains, six were identified as epiphytes or endophytes that efficiently removed phenol. The phenol removal experiment showed that the bacteria/duckweed system was more efficient during the first 24 h compared to the sterile duckweed control group. At the end of this experiment, almost 90% of the initial phenol concentration was removed by both groups, respectively. The bacteria stimulated the duckweed multiplication even at a high bacterial population density (>10⁵ CFU mL⁻¹) over a prolonged period of time (14 days). All bacterial strains were sensitive to all the applied antibiotics and formed biofilms in vitro. The dual bacteria/duckweed system, especially the one containing strain 43-Hafnia paralvei C32-106/3, Accession No. MF526939, had a number of characteristics that are advantageous in bioremediation, such as high phenol removal efficiency, biofilm formation, safety (antibiotic sensitivity), and stimulation of duckweed multiplication.

Fritillaria meleagris is a horticulturally and medicinally valuable bulbous plant that requires a period of low temperatures for proper growth and flowering. Since conventional methods of propagation are ineffective and very slow, tissue culture techniques offer an integrated approach to mass production of this valuable geophyte. In this study, we investigated the effects of various auxin–cytokinin combinations on different morphogenetic pathways in bulb scale culture. Bulbs obtained in vitro were cut longitudinally, and bulb scales were cultured for four weeks at 7 °C on MS medium supplemented with 6-benzylaminopurine (BAP) in combination with 2,4-dichlorophenoxyacetic acid (2,4-D) or α-naphthaleneacetic acid (NAA) at different concentrations in order to investigate the influence of plant growth regulators (PGRs) on different morphogenetic responses. Regeneration percentage, number of shoots per explant, shoot length, number of bulbs and number of somatic embryos were monitored weekly. After chilling, bulb scales were transferred to 24 °C, and all parameters were recorded again. Low PGR concentrations were very effective for shoot multiplication, yielding up to 5.5 shoots per explant. 2,4-D (at 2 mg/L) in combination with low BAP (0.25 mg/L) produced the highest number of bulbs (11.00 ± 0.00), while PGR-free medium was extremely effective in somatic embryo formation (13.50 ± 2.90). Detached somatic embryos and bulblets continued to grow and develop on fresh PGR-free medium. We present data demonstrating that low auxin–cytokinin concentrations and PGR-free medium provide an effective method for a combined morphogenetic pathway in F. meleagris that is suitable for large-scale propagation.

The rhizosphere represents a center of complex and dynamic interactions between plants and microbes, resulting in various positive effects on plant growth and development. However, less is known about the effects of indole-3-acetic acid (IAA) on aquatic plants. In this study, we report the characterization of four Pseudomonas strains isolated from the rhizosphere of the common duckweed (Lemna minor) with IAA-degradation and -utilization ability. Our results confirm previous reports on the negative effect of IAA on aquatic plants, contrary to the effect on terrestrial plants. P. putida A3-104/5 demonstrated particularly beneficial traits, as it exhibited not only IAA-degrading and -producing activity but also a positive effect on the doubling time of duckweeds in the presence of IAA, positive chemotaxis in the presence of IAA, increased tolerance to oxidative stress in the presence of IAA and increased biofilm formation related to IAA. Similarly, P. gessardii C31-106/3 significantly shortened the doubling time of duckweeds in the presence of IAA, while having a neutral effect in the absence of IAA. These traits are important in the context of plant–bacteria interactions and highlight the role of IAA as a common metabolite in these interactions, especially in aquatic environments where plants are facing unique challenges compared to their terrestrial counterparts. We conclude that IAA-degrading and -producing strains presented in this study might regulate IAA effects on aquatic plants and confer evolutionary benefits under adverse conditions (e.g., under oxidative stress, excess of IAA or nutrient scarcity).

The bulb is the main propagation organ of snake’s head fritillary (Fritillaria meleagris L.), a horticulturally attractive and rare geophyte plant species. In this study, we investigated the effect of soaking bulbs in GA₃ solution (1, 2, and 3 mg L⁻¹) combined with low-temperature treatment (7 °C) on breaking the dormancy of in vitro bulbs. Sugar status (total soluble sugars, glucose, and fructose content) was analyzed in different parts of the sprouted bulbs. The results showed that the soluble sugar concentration was highest in bulbs soaked in GA₃. The main sugar in fritillary bulbs was glucose, while fructose content was much lower. Glucose concentration dramatically increased after bulb chilling (7 °C), and its accumulation was predominantly detected in the lower sprout portion during the first weeks of sprouting. Sugar concentration was significantly lower in nonchilled bulbs, which indicates the importance of low temperature in bulb development and sprouting.

Drought is one of the main abiotic stresses affecting plant growth and development. Reduced plant yield and quality are primarily caused by the reductions in photosynthesis, mineral uptake, metabolic disorders, damages from the increased production of reactive oxygen species, and many other disruptions. Plants utilize drought resistance mechanisms as a defense strategy, and the systems’ activation is dependent upon several factors, including plant genotype, onthogenesis phase, drought intensity and duration, and the season in which the drought occurs. Impatiens walleriana is a worldwide popular flowering plant recognized for its vibrant flower colors, and is an indispensable plant in pots, gardens and other public areas. It prefers well-draining, moisturized soil, and does not perform well in overly dry or waterlogged conditions. Consequently, inadequate water supply is a common problem for this plant during production, transportation, and market placement, which has a substantial impact on plant performance overall. This review article outlines certain features of morphological, physiological, and molecular alterations induced by drought in ornamental, drought-sensitive plant species I. walleriana, as well as research carried out to date with the aim to improve the drought tolerance. Stress proteins aquaporins and dehydrins, whose molecular structure was described for the first time in this plant species, are highlighted specifically for their role in drought stress. Furthermore, the effective improvement of drought tolerance in I. walleriana by exogenous application of Plant Growth Regulators and Plant Growth-Promoting Bacteria is discussed in detail. Finally, this review can provide valuable insights for improving plant resilience and productivity in the face of water scarcity, which is critical for sustainable agriculture and horticulture.

Duckweed (L. minor) is a cosmopolitan aquatic plant of simplified morphology and rapid vegetative reproduction. In this study, an H. paralvei bacterial strain and its influence on the antioxidative response of the duckweeds to phenol, a recalcitrant environmental pollutant, were investigated. Sterile duckweed cultures were inoculated with H. paralvei in vitro and cultivated in the presence or absence of phenol (500 mg L⁻¹), in order to investigate bacterial effects on plant oxidative stress during 5 days. Total soluble proteins, guaiacol peroxidase expression, concentration of hydrogen peroxide and malondialdehyde as well as the total ascorbic acid of the plants were monitored. Moreover, bacterial production of indole-3-acetic acid (IAA) was measured in order to investigate H. paralvei’s influence on plant growth. In general, the addition of phenol elevated all biochemical parameters in L. minor except AsA and total soluble proteins. Phenol as well as bacteria influenced the expression of guaiacol peroxidase. Different isoforms were associated with phenol compared to isoforms expressed in phenol-free medium. Considering that duckweeds showed increased antioxidative parameters in the presence of phenol, it can be assumed that the measured parameters might be involved in the plant’s defense system. H. paralvei is an IAA producer and its presence in the rhizosphere of duckweeds decreased the oxidative stress of the plants, which can be taken as evidence that this bacterial strain acts protectively on the plants during phenol exposure.