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Crassocephalum rubens, a herb with potential anticancer properties, encounters challenges in production efficiency due to small seed size and elevated temperatures in cultivation areas. Our study investigates the effects of seed pelleting and plant growth-promoting bacteria (PGPB) on germination and seedling growth across temperature variations in Taiwan. Pelleted seeds demonstrate superior germination percentages linked to enhanced seed quality. Elevated temperature, particularly at 30/25 °C, enhanced germination performance, with the highest final germination percentage observed in pelleted seeds treated with water. Unexpectedly, PGPB strains—Klebsiella sp. KsGRB10 and Bacillus sp. BsGFB04—exhibited limited impact on germination rates, showing a marginal increase in seedling growth under 25/20 °C and 30/25 °C, respectively. Air temperature fluctuations influenced seedling vigor, leaf color, and physiological parameters. Remarkably, inoculation with BsGFB04 and KsGRB10 enhanced C. rubens' tolerance to high-temperature stress conditions. Diurnal measurements in week 4, under 25/20 °C, reveal that PGPB inoculation decreased stomatal conductance and transpiration rate while maintaining the quantum yield of PSII, indicating potentially improved water-use efficiency. This study provides crucial insights into the interplay among PGPB, environmental stress, and the physiology of a wild species, paving the way for further research in the domestication of C. rubens for medicinal herb mass production. [ABSTRACT FROM AUTHOR]

The positive effects of high atmospheric CO2 concentrations [CO2] decrease over time in most C3 plants because of down-regulation of photosynthesis. A notable exception to this trend is plants hosting N-fixing bacteria. The decrease in photosynthetic capacity associated with an extended exposure to high [CO2] was therefore studied in non-nodulating rice that can establish endophytic interactions. Rice plants were inoculated with diazotrophic endophytes isolated from the Salicaceae and CO2 response curves of photosynthesis were determined in the absence or presence of endophytes at the panicle initiation stage. Non-inoculated plants grown under elevated [CO2] showed a down-regulation of photosynthesis compared to those grown under ambient [CO2]. In contrast, the endophyte-inoculated plants did not show a decrease in photosynthesis associated with high [CO2], and they exhibited higher photosynthetic electron transport and mesophyll conductance rates than non-inoculated plants under high [CO2]. The endophyte-dependent alleviation of decreases in photosynthesis under high [CO2] led to an increase in water-use efficiency. These effects were most pronounced when the N supply was limited. The results suggest that inoculation with N-fixing endophytes could be an effective means of improving plant growth under high [CO2] by alleviating N limitations. [ABSTRACT FROM AUTHOR]

While many studies on zebra chip (ZC) disease in potatoes have focused on the epidemiology of the disease and the characterization of infected potato plants, this study quantifies the impact of ZC disease on crop response and investigates the relationship between irrigation level and ZC disease severity. In this two-year study chipping potatoes were planted under a variable rate irrigation center pivot sprinkler using a split-plot design with a 2 × 3 factorial combination of ZC disease level (diseased and non-diseased) and irrigation levels of 100%, 80% and 60% replenishment of soil water depletion to field capacity, designated I 100 , I 80 and I 60. Crop response of tuber yield, evapotranspiration (ET c), crop water productivity (CWP) and irrigation water productivity (IWP) from ZC diseased plots were compared with non-diseased (control) plots. Tuber yield and CWP in the infested plots were significantly reduced by at least 58% in 2018 and by 21% in 2019 as compared with results in the control plots. Year significantly affected crop response in the control plots, however, crop response in the ZC diseased plots was devastative to potatoes from year to year. There was no interaction between irrigation level and ZC disease occurrence. In both years, stomatal conductance measurements in ZC diseased plants were reduced 35 and 44 days after infection as compared with control plants. Since irrigation did not lessen the severity of ZC disease, as soon as diseased plants are identified within a field, withholding irrigation to the affected areas could improve IWP at the field level. Future studies should consider the use of thermal imaging or spectral reflectance of the plant canopy for spatiotemporal detection of ZC disease as early as possible in the growing season. • Zebra chip disease reduced fresh tuber yield by at least 58% in 2018 and by 21% in 2019. • Stomatal conductance and the ability to uptake water were limited in ZC diseased potato plants. • The interaction between Zebra chip disease and irrigation level was not significant. [ABSTRACT FROM AUTHOR]

Endophytes are symbiotic microbes that live inside host plants. These endophytic symbionts receive photosynthesized carbohydrates from host plants while conferring symbiotic benefits to their host. During photosynthate-fueled respiration, endophytes release CO 2 into the intercellular spaces of their host plants in which they reside. We evaluated the possibility for host plants' re-assimilation of microbial respiratory CO 2 . In planta and in vitro assays were conducted to examine respiratory characteristics of endophyte-symbiotic plants. Endophyte-inoculated plants had a greater in planta respiration rate. In vitro data demonstrated that respiration rates of endophytes are dependent on the total amount of endophytes and the concentration of carbohydrate supply. Assuming the host plant offers sufficient carbohydrates, we estimate that CO 2 produced during microbial respiration in planta accounts for about 57% of the CO 2 assimilated by the photosynthetic pathways of the symbiotic plant. This suggests that endophytes can produce significant amounts of CO 2 , which could then be re-assimilated by host plants.