Phytoremediation potential of hybrid Pennisetum in cadmium-contaminated soil and its physiological responses to cadmium.

Cadmium (Cd) contamination in soil is a global problem. Recently, phytoremediation with plants, possessing high biomass and moderate Cd enrichment ability, has received excessive attention as a cost-effective method for Cd remediation from the soil. In this study, the plant growth, physiological responses, Cd concentration, accumulation, and distribution of the C4 grass hybrid Pennisetum (HP) were studied in different levels of Cd-contaminated soil in a pot experiment. Furthermore, a field trial was also conducted to accurately assess its practical phytoremediation potential in natural Cd-contaminated fallow filed. The results showed that HP possessed effective antioxidant enzymes to scavenge ROS and strong physiological coordination in response to Cd stress. The HP had a considerable Cd enrichment ability, and the maximal Cd uptake of 1.08 mg plant-1 was achieved at 60 mg kg-1 Cd in the pot. The maximal concentration of Cd in the aboveground parts and roots of HP were 49.33 mg kg-1 and 103.33 mg kg-1, respectively, when soil Cd was 70 mg kg-1 in the pot. The bioconcentration factor (BCF) of Cd in the aboveground parts was less than 1, while the BCF in the root was greater than 1, and the translocation factor (TF) was less than 0.5 in all Cd treatment groups. A total of 46.89-65.46% absorbed Cd stored in the aboveground parts in the pot. The Cd concentration in roots of HP was significantly higher compared to those in leaves and stems, and all BCFs were greater than 1.5 in a lightly Cd-contaminated field (0.35 mg kg-1). Furthermore, HP had high aboveground dry biomass up to 54.63 t ha-1 and accumulated 16.13 g ha-1 Cd in its aboveground parts in the field, which was accounted for about 91.54% of the total Cd extracted by the plant. The soil Cd concentration was reduced by 60.00% after planting HP. Our results suggest that HP is a potential phytoextractor for Cd in lightly Cd-contaminated soil as well as a phytostabilizer under strong Cd stress in the pot.

Evaluation of biological and chemical additives on microbial community, fermentation characteristics, aerobic stability, and in vitro gas production of SuMu No. 2 elephant grass.

BACKGROUND: The study was conducted to evaluate the effects of biological and chemical additives on microbial community, fermentation characteristics, aerobic stability, and in vitro gas production of SuMu No. 2 elephant grass. RESULTS: Aerobic bacteria and yeast were not affected on days 5 and 7 but were significantly (P < 0.224) reduced on days 14, 30, and 60, whereas lactic acid and lactic acid bacteria were significantly (P > 0.001) higher in all ensiling days within all treatment groups. During the ensiling days, the pH, acetic acid, butyric acid, and yeast were decreased in all treatment groups, whereas the Lactobacillus plantarum group and L. plantarum + natamycin group were highly significantly (P > 0.001) decreased. During air exposure, the water-soluble carbohydrates, ammonia nitrogen, lactic acid, and acetic acid were not affected on days 1-4, whereas pH and aerobic bacteria (were significantly (P < 0.05) increased on days 2-4. The addition of Lactobacillus plantarum and natamycin increased the gas production, in vitro dry matter digestibility, and in vitro neutral detergent fiber of SuMu No. 2 elephant grass silages. CONCLUSIONS: The addition of biological and chemical additives, such as L. plantrum alone and the combination with natamycin, affected the undesirable microbial community, fermentation characteristics, aerobic stability, and in vitro gas of SuMu No. 2 elephant grass. © 2021 Society of Chemical Industry.

Improving hybrid Pennisetum growth and cadmium phytoremediation potential by using Bacillus megaterium BM18-2 spores as biofertilizer.

Environmental pollution with heavy metals becomes an issue of serious concern worldwide. Cadmium is considered one which adversely affects living organisms. Recently, the usage of endophytic bacteria to enhance the plant growth and phytoremediation of heavy metals contaminated sites is gaining great attention. The current study focused on utilizing the spores of Bacillus megaterium BM18-2 as biofertilizer for enhancing the growth of Cd hyperaccumulator Hybrid Pennisetum and Cd tolerance of the plant. Therefore, the production of the highest proportion of BM18-2 spores in short incubation time was investigated using different culture media. The results revealed that the maximum proportion of BM18-2 spores (90%) was obtained following incubation for 48 h in Tryptone- yeast extract media (TY). Furthermore, several growth parameters of H. Pennisetum were shown to be significantly improved by inclusion of BM18-2 spores into Cd contaminated soil in contrast to non- inoculated plant. The chlorophyll concentration of the leaves rose by 5%, 13%, and 22.89% with increasing Cd concentration of soil (20, 40 and 60 mg/Kg, respectively). The percentage of total nitrogen content of the root, stem and leaf was increased due to the bacterial spores inoculation and the highest percentage was recorded in the leaf in all treatments. Moreover, Cd phytoremediation capacity of H. Pennisetum greatly enhanced with the application of BM18-2 spores into the soil. An obvious correlation was also observed between Cd accumulation and bacterial colonization where the Cd accumulation enhanced by 21.9%, 16.5%, and 94.6% and the maximum count of BM18-2 (27 × 105, 194 × 104,and 145 × 104 CFU/g) were recorded in the root system in 20, 40, and 60 mg/Kg Cd spiked soil, respectively. Consequently, the spores of BM18-2 was proven to succeed as biofertilizer to improve growth of H. pennisetum during Cd stress which subsequently improved the phytoremediation of Cd contaminated soil.

Potential effect of the microbial fermented feed utilization on physicochemical traits, antioxidant enzyme and trace mineral analysis in rabbit meat.

The study investigated the potential effect of the microbial fermented feed utilization on physicochemical traits, antioxidant enzyme and trace mineral analysis in rabbit meat. A total of 72 six-week-old male rabbits were weighed and randomly divided into four groups (1) (SRKC) control; (2) (SRKP) Lactobacillus plantarum 1 × 106  cfu/g fresh weight (FW); (3) (SRKG) Pediococcus acidilactici 1 × 106 cfu/g FW and (4) (SRKPG) P. acidilactici + L. plantarum 1 × 106 cfu/g FW. Performance characteristic, weekly body weight, was positively (p < .05) enhanced, while daily feed intake (DFI) and feed convention ratio (FCR) were not influenced in treatments group as compared to untreated. The water, protein, water holding capacity (WHC) and dry matter (DM) concentration were positively (p < .05) influenced, while ash, pH, lightness, redness and yellowness were not influenced in treated group as compared to untreated. The concentration of glutathione peroxidase (Gpx), superoxide dismutase (SOD) and aspartate aminotransferase (AST) was positively (p < .05) influenced in treatments group as compared to control. Regarding trace minerals, copper (Cu), iron (Fe), manganese (Mn) and zinc (Zn) were positively (p > .05) reduced in treated group as compared to untreated. It is concluded that the addition of lactic acid bacteria (L. plantarum and P. acidilactici) in Hybrid pennisetum silage had a constructive influence on rabbit health performance and meat biochemistry.

Endophytic Bacillus megaterium BM18-2 mutated for cadmium accumulation and improving plant growth in Hybrid Pennisetum.

Hybrid Pennisetum (Pennisetum americanum × P. purpureum Schumach L.) is a tall and rapidly growing perennial C4 bunch grass. It has been considered as a promising plant for phytoremediation of heavy metal-contaminated soil due to its high biomass, high resistance to environmental stress, pests and diseases. Heavy metal bioavailability level is the most important parameter for measurement of the phytoremediation efficiency. Endophytic bacteria were used to further enhance phytoremediation of heavy metals through bioaccumulation or bioabsorption process. In the present study, the endophytic Bacillus megaterium strain 'BM18' isolated from hybrid Pennisetum was screened under 10-70 µM cadmium (Cd) stress for Cd-resistant mutant colonies. And one such mutant colony'BM18-2' was obtained from the screen. Comparably, 'BM18-2' was more Cd-tolerant and had higher Cd removal ability than the original strain'BM18'. The amount of IAA and ammonia production, and phosphate solubilization were 1.09, 1.23 and 1.24 times in 'BM18-2' than those of 'BM18', respectively. Full genome sequencing of these two strains revealed 6 different genes: BM18GM000901, BM18GM005669 and BM18GM005870 encoding heavy metal efflux pumps, BM18GM003487 and BM18GM005818 encoding transcriptional regulators for metal stress biosensor and BM18GM001335 encoding a replication protein. Inoculation with 'BM18-2' or 'BM18' both significantly reduced the toxic effect of Cd on hybrid Pennisetum, while the effect of 'BM18-2' on plant growth promotion in the presence of Cd was significantly better that of 'BM18'. Therefore, the mutated strain 'BM18-2' could be used as a potential agent for Cd bioremediation, improving growth and Cd absorption of hybrid Pennisetum in Cd contaminated soil.

IAA stimulates pollen tube growth and mediates the modification of its wall composition and structure in Torenia fournieri.

The effects of several hormones on pollen tube growth were compared in Torenia fournieri and it was found that IAA was the most effective, stimulating pollen tube growth and causing the shank part of pollen tubes to be slender and straighter. The role of IAA was investigated by studying the changes in ultrastructure and PM H(+)-ATPase distribution in the pollen tubes and the modification of the tube wall. Using the fluorescent marker FM4-64, together with transmission electron microscopy, it was shown that secretory vesicles and mitochondria increased in IAA-treated tubes. Immunolocalization and fluorescence labelling, together with Fourier-transform infrared analysis, detected that IAA enhanced the level of PM H(+)-ATPase and the synthesis of pectins, and reduced the cellulose density in pollen tubes. Importantly, to observe the orientation of cellulose microfibrils in pollen tubes in situ, atomic force microscopy was used to examine the 'intact' tube wall. Atomic force microscopy images showed that cellulose microfibrils were parallel to each other in the subapical region of IAA-treated tubes, but disorganized in control tubes. All results provided new insights into the functions of cellulose microfibrils in pollen tube growth and direction, and revealed that the IAA-induced changes of pollen tubes were attributed to the increase in secretory vesicles, mitochondria, and PM H(+)-ATPase, and the modification of pectin and cellulose microfibrils in the tube wall.