Environmental Growth Chambers Research Articles

Adaptation to Environmental Stressors Conferred by Gene Copy Number Variation in Herbicide Resistant Amaranthus palmeri

Many rampant agricultural weeds have been found to contain gene copy number variation, a genetic adaptation that can facilitate the evolution of stress resistance. Amaranthus palmeri is a highly competitive and problematic agricultural weed in the United States which continues to naturalize, spreading northward to Canada. A.palmeri has gained attention due to its rapid evolution of herbicide resistance— a mechanism conferred by gene copy number variation of EPSPS. Researchers hypothesize that this gene is contained within an amplicon alongside other stress tolerance related genes. This raises the question of whether increased EPSPS gene copy number is associated with higher tolerance to environmental stressors, beyond herbicide stress. To prepare for addressing this hypothesis, I conducted a pilot project testing the ideal conditions for germination of A.palmeri. I planted 200 seeds divided between greenhouse and growth chamber environments. Many seeds benefit from a period of cold as a signal to break dormancy, thus, each category was further divided into two treatments: control and cold stratified (seeds were incubated in a –23 cold room for a week). I was interested in whether the increased consistency of temperature, light intensity, and photoperiod provided by a growth chamber, relative to a greenhouse, would increase germination rates. Results indicate that greenhouse grown seedlings had a 71% germination rate and within each treatment, 86% of cold stratified plants germinated while only 56% of the control group germinated. Whereas in the growth chamber, surprisingly only 26% of plants germinated with a breakdown of 22% cold stratified and 30% control. Thus, to germinate enough plants for a large-scale experiment, I chose to cold stratify seeds and grow them in the greenhouse for my undergraduate thesis. In this common garden experiment, I am currently growing 500 plants which will be divided into four stress treatment categories: control, salinity, drought, and salinity x drought. Using phenotypic measurements and digital droplet PCR (ddPCR) to quantify EPSPS gene copy number, I will test for a possible association between plants with a higher tolerance to these simulated environmental stressors and the presence of increased EPSPS gene copy number.

Plasticity-mediated persistence and subsequent local adaptation in a global agricultural weed.

Phenotypic plasticity can alter traits that are crucial to population establishment in a new environment, before adaptation can occur. How often phenotypic plasticity enables subsequent adaptive evolution is unknown, and examples of the phenomenon are limited. We investigated the hypothesis of plasticity-mediated persistence as a means of colonization of agricultural fields in one of the world's worst weeds, Raphanus raphanistrum ssp. raphanistrum. Using non-weedy native populations of the same species and subspecies as a comparison, we tested for plasticity-mediated persistence in a growth chamber reciprocal transplant experiment. We identified traits with genetic differentiation between the weedy and native ecotypes as well as phenotypic plasticity between growth chamber environments. We found that most traits were both plastic and differentiated between ecotypes, with the majority plastic and differentiated in the same direction. This suggests that phenotypic plasticity may have enabled radish populations to colonize and then adapt to novel agricultural environments.

Dynamics of micro and macronutrients in a hydroponic nutrient film technique system under lettuce cultivation

While hydroponics is considered an efficient vegetable production system, there is a compelling need to investigate the efficiency of the current generic nutrient dosing recommendation primarily based on electrical conductivity (EC) measurements. Such information is critical to fine-tune and optimize the current hydroponic management practices for improved nutrient uptake efficiency. This study investigated the dynamics of some micro and macronutrients (N, P, Ca, Mg, K, Fe, and Mn) in a recirculating nutrient film technique (NFT) hydroponic system under lettuce cultivation. The research was conducted in an indoor controlled environment growth chamber with lettuce grown in different EC levels (1.2 and 1.6 dS m−1). Each treatment had four hydroponic cultivation units, each one with 24 plants. Nutrient solution and tissue samples were collected two to three times per week. Nutrient dynamics, including nutrient uptake efficiencies and environmental losses, were calculated using a mass balance approach. The effects of EC level on fresh and dry lettuce biomass and nutrient uptake were insignificant. Observed variations in nutrient solution composition during lettuce cultivation included the almost complete removal of ammonia nitrogen, nitrate decreases towards the end of the experiment, consistent increases in aqueous Ca concentration, and corresponding decreases in K and Mn. Average N losses ranged between 27 and 40 %, presumably through denitrification, while 10–14 % of N was assimilated into the plant biomass. The remaining N in the recirculating nutrient solution was estimated to be between 50 and 59 %. The average P loss was 11–35 %, likely due to precipitation, while 52–77 % remained in the nutrient solution. Nutrient uptake efficiencies averaged 19–31 % K, 12–21 % P, 9–16 % Mn, 4–6 % Ca, 3–4 % Mg, and 2–4 % Fe. These results suggest that elevated nutrient concentrations in recirculating nutrient solutions led to losses and underutilization. Findings from this study provide a comprehensive dataset critical to improving hydroponic nutrient management beyond N and P. Hydroponic nutrient management should target providing essential nutrients needed by plants at the correct proportions considering the plant growth stage.

Demographic responses to competition with surrounding vegetation in subalpine plant species

Alterations in biotic interactions alongside climatic factors are proposed to affect the extinction risks of alpine and subalpine plant species. We examined the population demography of Primula farinosa along gradients of vegetation coverage to assess how the population viability of high mountain plants would alter in response to changing competitive intensities. Size-based integral projection models were constructed for plots with varying vegetation coverages. Complementary to the demographic survey, the performance of P. farinosa was evaluated in controlled environments when grown with its naturally co-occurring plant, Sanguisorba hakusanensis. In field sites, population growth rates (λ) of P. farinosa declined as surrounding vegetation coverage increased. The means, elasticities, and life-table response experiment (LTRE) contributions of the vital rates also changed, but the alteration patterns depended on the vital rates. Juvenile survival (JS), adult survival (AS), and flowering probability (FP) were lower in plots with denser vegetation while the decrease of AS was not statistically significant. Notably, the elasticity of AS exhibited a positive, whereas the elasticities of JS and FP exhibited negative regression coefficients for vegetative coverage. AS and FP showed more pronounced LTRE contributions in declining λ than JS. Significant reductions in JS and FP were also observed when plants were grown with S. hakusanensis in growth-chamber environments. Both field and chamber studies demonstrated a competitive interaction between P. farinosa and neighboring vegetation, affecting diverse demographic parameters. Altered elasticities would mitigate or exacerbate the impact of decreased mean vital rates on λs in denser vegetation, emphasizing the importance of evaluating both elasticity and the mean of vital rates to predict population persistence under changing biotic interactions.

Effect of different light intensities on agronomic characteristics and antioxidant compounds of Brassicaceae microgreens in a vertical farm system

Microgreens are vegetable or edible herb shoots harvested in the early stages of development. They have an important number of bioactive compounds and add color, texture, and flavor to dishes and salads. Given their benefits, small size, and high market prices, they can grow in indoor systems, where light is determinant. This study aimed to evaluate the effect of different light intensities on agronomic characteristics, color, chlorophylls and carotenoids content, and antioxidant activity represented by total phenolic content (TPC), eliminate, and antioxidant capacity (AC) in four Brassicaceae species in two colors (green and red). The experiment was conducted in a controlled light-emitting diode (LED) environment growth chamber (day/night temperatures of 25/20 ± 1.2°C, 16 h photoperiod, and 79 ± 2% relative humidity). Three light intensities were used for microgreen growth with the same LED light spectrum: low (120 ± 5.1 μmol m−2 s−1), medium (160 ± 3.6 μmol m−2 s−1), and high (210 ± 5.9 μmol m−2 s−1). Eight g of the seeds of green and red cultivars of cabbage, kale, mizuna, and mustard were sown in a plastic tray (64 cm x 35 cm x 6 cm) with a mixture of peat and perlite (1:2 = v: v). Overall, the high intensity increased dry matter percentage and dry weight, except in green and red kale and green cabbage cultivars. In contrast, low intensity promoted a larger hypocotyl in all species than with high intensity; moreover, it enhanced the cotyledon area in green and red mizuna. Cabbage, kale, and mustard green cultivars were greener under medium intensity, whereas the low intensity enhanced the purple color of mizuna. In addition, chlorophyll a and b increased under low intensity in most species except the red kale and mustard cultivars. The high intensity raises the antioxidant activity, promoting a higher TPC and AC. The findings revealed that the light intensity generated variations in agronomic characteristics, color, chlorophyll content, and antioxidant activity of Brassicaceae microgreens, and the changes were based on the specific species and cultivars.

Root Silicon Amendment Enhances Barley’s Resistance to Fusarium Head Blight in the Field

Background: Silicon (Si) amendment plays an important role in enhancing the resistance of several plant species to diverse pathogens. To date, a few studies have focused on how Si application helps barley, a higher Si absorber and accumulator monocot, to resist fungal diseases, including Fusarium head blight (FHB), which reduces the quality and safety of harvested products worldwide. However, no study has ever been conducted to demonstrate Si's ability to suppress FHB development in barley heads under uncontrolled climatic conditions. Materials and Methods: This 2-year field study elucidated the effect of multiple Si applications at 1.7 mM via roots in two barley cultivars, Arabi Aswad (AS moderately resistant) and Arabi Abiad (AB moderately susceptible), to control four Fusarium species with diverse pathogenicity. The incidence of FHB (DI type I resistance), severity of FHB (DS type II), and Fusarium-damaged kernels (FDK type III) were also tested to describe the nature of the Si-enhanced barley resistance. Results: Si treatment at 1.7 mM under soil culture decreased FHB development by enhancing all resistance types measured in the present research. DI, DS, and FDK were reduced by 18.7%, 20.3%, and 20.2%, respectively, in Si-Fusarium-inoculated treatments relative to fungal-inoculated controls. Si absorption in barley strengthened the defense system measured by type I and type II on AB to a level comparable to AS not amended with Si. Irrespective of the barley cultivar, however, Si resulted in a quasi-similar reduction of FDK. Importantly, Si treatment at 1.7 mM decreased the damage of FHB in previous analyses conducted on AS and AB under in vitro and growth chamber environments, showing that Si enhanced the expression of resistance to FHB infection in seedlings and adult barley plants. Conclusion: All of these results are promising outcomes for the application of Si as a safe and effective method against Fusarium species. This study provides new insights into the potential of multiple Si applications at 1.7 mM via roots for boosting barley’s resistance to FHB with a bright prospect for Si use in barley cultivation under field conditions.

Optimizing Light Use Efficiency and Quality of Indoor Organically Grown Leafy Greens by Using Different Lighting Strategies

Vertical farming is experiencing significant growth, and the optimization of artificial lighting is essential for enhancing the sustainability of this growing system. Therefore, the aim of this study was to examine how light segmentation, the incorporation of a low-intensity lighting phase known as the light compensation point (LCP) instead of the traditional dark phase, and variations in the light spectrum impact the agricultural outcomes of organically cultivated leafy greens. In controlled growth chamber environments, a variety of leafy plant species (Spinacia oleracea L., Ocimum basilicum, Beta vulgaris L., Lactuca sativa L. cv. ‘Garrison’ and ‘Blade’, Brassica rapa cv. ‘Japonica’ and ‘Chinensis’, Brassica juncea cv. ‘Scarlet Frills’ and ‘Wasabina’, Eruca sativa and Perilla frutescens L.) were subjected to four light treatments with varying intensities and durations of lighting, while in a second experiment, five different spectral growing conditions were compared. Irrespective of the plant species, shortening the length of the diel cycle by extending the cumulative daily lighting to 20–24 h per day (5L/1N [5 h at 261 µmol m−2 s−1 + 1 h darkness for a total of 20 h of light per day] and 5L/1LCP [5 h at 256 µmol m−2 s−1 + 1 h LCP at 20 µmol m−2 s−1 for a total of 24 h of light per day]) led to an average increase of +12% in height, fresh weight (+16%), dry weight (+23%), and specific leaf weight (+11%), compared to the control plants (18L/6N; 18 h at 289 µmol m−2 s−1 + 6 h darkness) and 6L/6LCP plants (6 h at 418 µmol m−2 s−1 + 6 h LCP at 20 µmol m−2 s−1 for a total of 24 h of light per day) during the first harvest. This also resulted in better light utilization, expressed as increased fresh (+16%) and dry (+24%) biomass per mol of light received. Conversely, the studied light spectral treatments had no effect on the growth parameters of the four selected species. In conclusion, our study showed that reducing light intensity while extending the photoperiod could potentially represent a cost-effective LED strategy for the indoor cultivation of organically or conventionally grown leafy greens.

Effects of elevated CO2 concentration and experimental warming on morphological, physiological, and biochemical responses of winter wheat under soil water deficiency.

Global climate change and freshwater scarcity have become two major environmental issues that constrain the sustainable development of the world economy. Climate warming caused by increasing atmospheric CO2 concentration can change global/regional rainfall patterns, leading to uneven global seasonal precipitation distribution and frequent regional extreme drought events, resulting in a drastic reduction of available water resources during the critical crop reproduction period, thus causing many important food-producing regions to face severe water deficiency problems. Understanding the potential processes and mechanisms of crops in response to elevated CO2 concentration and temperature under soil water deficiency may further shed lights on the potential risks of climate change on the primary productivity and grain yield of agriculture. We examined the effects of elevated CO2 concentration (e[CO2]) and temperature (experimental warming) on plant biomass and leaf area, stomatal morphology and distribution, leaf gas exchange and mesophyll anatomy, rubisco activity and gene expression level of winter wheat grown at soil water deficiency with environmental growth chambers. We found that e[CO2] × water × warming sharply reduced plant biomass by 57% and leaf photosynthesis (P n) 50%, although elevated [CO2] could alleviated the stress from water × warming at the amount of gene expression in RbcL3 (128%) and RbcS2 (215%). At ambient [CO2], the combined stress of warming and water deficiency resulted in a significant decrease in biomass (52%), leaf area (50%), P n (71%), and G s (90%) of winter wheat. Furthermore, the total nonstructural carbohydrates were accumulated 10% and 27% and increased R d by 127% and 99% when subjected to water × warming and e[CO2] × water × warming. These results suggest that water × warming may cause irreversible damage in winter wheat and thus the effect of "CO2 fertilization effect" may be overestimated by the current process-based ecological model.

Sensitivity of Clarireedia spp. to benzimidazoles and dimethyl inhibitors fungicides and efficacy of biofungicides on dollar spot of warm season turfgrass.

Dollar spot caused by Clarireedia spp. (formerly Sclerotinia homoeocarpa) is an economically destructive fungal disease of turfgrass that can significantly compromise turf quality, playability, and aesthetic value. Fungicides are frequently used to manage the disease but are costly and potentially unfavorable to the environment. Repeated use of some active ingredients has resulted in reduced efficacy on C. jacksonii causing dollar spot in cool-season turfgrasses in the US. Experiments were conducted to study fungicide sensitivity of Clarireedia spp. as well as to develop alternatives to fungicides against dollar spot on warm-season turfgrass in Georgia. First, 79 isolates of Clarireedia spp. collected across the state were tested on fungicide-amended agar plates for their sensitivity to thiophanate-methyl (benzimidazole) and propiconazole (dimethyl inhibitor). Seventy-seven isolates (97.5%) were sensitive (0.001 to 0.654 μg/mL) and two isolates (2.5%) were found resistant (>1000 μg/mL) to thiophanate-methyl. However, in the case of propiconazole, 27 isolates (34.2%) were sensitive (0.005 to 0.098 μg/mL) while 52 isolates (65.8%) were resistant (0.101 to 3.820 μg/mL). Next, the efficacy of three bio- and six synthetic fungicides and ten different combinations were tested in vitro against C. monteithiana. Seven bio- and synthetic fungicide spray programs comprising Bacillus subtilis QST713 and propiconazole were further tested, either alone or in a tank mix in a reduced rate, on dollar spot infected bermudagrass 'TifTuf' in growth chamber and field environments. These fungicides were selected as they were found to significantly reduce pathogen growth up to 100% on in vitro assays. The most effective spray program in growth chamber assays was 100% B. subtilis QST713 in rotation with 75% B. subtilis QST713 + 25% propiconazole tank mix applied every 14 days. However, the stand-alone application of the biofungicide B. subtilis QST713 every seven days was an effective alternative and equally efficacious as propiconazole, suppressing dollar spot severity and AUDPC up to 75%, while resulting in acceptable turf quality (>7.0) in field experiments. Our study suggests that increased resistance of Clarireedia spp. to benzimidazoles and dimethyl inhibitors warrants continuous surveillance and that biofungicides hold promise to complement synthetic fungicides in an efficacious and environmentally friendly disease management program.

Individual and Interactive Ecophysiological Effect of Temperature, Watering Regime and Abscisic Acid on the Growth and Development of Tomato Seedlings

Climate change is a major concern to people all over the world. Most studies have considered singular or dual effects of climate change implications on plant growth and development; however, the combination of multiple factors has received little attention. We therefore studied the single and combined effects of two environmental stress factors (high temperature and water stresses) and abscisic acid on tomato seedlings (Solanum lycoperscum L.). Plants were grown in controlled environment growth chambers under two temperatures (22/18 °C or 28/24 °C; 16 h light/8 h dark), two watering regimes (well-watered or water-stressed), and two abscisic acid treatments (0 and 100 µL of 1mM abscisic acid solution, every other day). Plants were placed under experimental conditions for a total of 33 days, including a 13-day period of initial growth and hardening. Morphological, biochemical, and physiological parameters were measured to assess the growth and development of plants in response to the three factors. ANOVA and Scheffé’s multiple-comparison procedures were used to establish significant differences among treatments and among the three factors being manipulated. All three factors decreased plant height and growth rate. Dry mass accumulation was negatively affected by high temperatures. Transpiration, stomatal conductance, and gas exchange parameters were negatively affected by all three factors; additionally, net carbon dioxide assimilation was reduced by water stress and abscisic acid application. Non-photochemical quenching was decreased in plants grown under higher temperature and in abscisic acid-treated plants. Though it was not significant, abscisic acid appears to mitigate the negative effect of higher temperature and water stress on the nitrogen balance index and total chlorophyll content.

Assembly and operation of an imaging system for long-term monitoring of bioluminescent and fluorescent reporters in plants

BackgroundNon-invasive reporter systems are powerful tools to query physiological and transcriptional responses in organisms. For example, fluorescent and bioluminescent reporters have revolutionized cellular and organismal assays and have been used to study plant responses to abiotic and biotic stressors. Integrated, cooled charge-coupled device (CCD) camera systems have been developed to image bioluminescent and fluorescent signals in a variety of organisms; however, these integrated long-term imaging systems are expensive.ResultsWe have developed self-assembled systems for both growing and monitoring plant fluorescence and bioluminescence for long-term experiments under controlled environmental conditions. This system combines environmental growth chambers with high-sensitivity CCD cameras, multi-wavelength LEDs, open-source software, and several options for coordinating lights with imaging. This easy-to-assemble system can be used for short and long-term imaging of bioluminescent reporters, acute light-response, circadian rhythms, delayed fluorescence, and fluorescent-protein-based assays in vivo.ConclusionsWe have developed two self-assembled imaging systems that will be useful to researchers interested in continuously monitoring in vivo reporter systems in various plant species.

Inheritance of 2,4-dichlorophenoxyacetic acid (2,4-D) resistance in Amaranthus palmeri

In this study, the inheritance of 2,4-D resistance in a multiple herbicide-resistant Palmer amaranth (KCTR) was investigated. Direct and reciprocal crosses were performed using 2,4-D-resistant KCTR and susceptible KSS plants to generate F1 progenies. 2,4-D dose–response assays were conducted to evaluate the response of progenies from each F1 family along with KCTR and KSS plants in controlled environmental growth chambers. Additionally, 2,4-D-resistant male and female plants from each of the F1 families were used in pairwise crosses to generate pseudo-F2 families. Segregation (resistance or susceptibility) of progenies from the F2 families in response to a discriminatory rate of 2,4-D (i.e., 560 g ae ha−1) was evaluated. Dose–response analysis of F1 progenies derived from direct and reciprocal crosses suggested that the 2,4-D resistance in KCTR is a nuclear trait. Chi-square analyses of F2 segregation data implied that 2,4-D resistance in KCTR is controlled by multiple gene(s). Overall, our data suggest that the 2,4-D resistance in KCTR Palmer amaranth is a nuclear inherited trait controlled by multiple genes. Such resistance can spread both via pollen or seed-mediated gene flow. In future, efforts will be directed towards identifying genes mediating 2,4-D resistance in KCTR population.

ZnO Nanoparticle Size-Dependent Effects on Swiss Chard Growth and Nutritional Quality

Understanding the interactions between nanoparticles (NPs) and plants is crucial in comprehending the impact of nanotechnology on agriculture, with a focus on plant toxicity concerns and risks to human health. Zinc (Zn) belongs to the micronutrients with poor bioavailability, though this element is essential for the vital functions of plants. In this respect, this research estimated the impact of the size of zinc oxide NPs (ZnO NPs) applied by foliar application on biomass production and nutritional qualities in baby leaf Swiss chard (Beta vulgaris ssp. cicla L. cv. Barese). Plants were grown hydroponically in controlled environment growth chambers, and exposed via foliar spray to varying particle sizes of ZnO NPs (18, 35–45, and 80–200 nm) at a concentration of 200 ppm. Control plants were sprayed with distilled water. The results revealed that ZnO NPs improved fresh and dry biomass, leaf area, favored leaf chlorophyll and flavonol indexes, and improved the total soluble protein content in Swiss chard. The total phenolic content and antioxidant properties depended more on different sizes of ZnO NPs in the solutions used for spraying plants. ZnO NPs significantly increased the accumulation of Zn and Fe in edible tissues. Still, the hazard quotient values of Zn and Fe were lower than 1, which supports the safe consumption of Swiss chard after ZnO NP treatment. In conclusion, these results revealed that ZnO NPs could be applied in Swiss chard production to improve yield, quality, and nutraceutical properties.

The Influence of End-of-Day Blue Light on the Growth, Photosynthetic, and Metabolic Parameters of Lettuce at Different Development Stages.

This study evaluates the effect of end-of-day blue (EOD B) light on the physiological response of lettuce (Lactuca sativa, Lobjoits Green Cos) at different phenological development stages. Plants were grown in a controlled environment growth chamber (day/night temperature 21 ± 2 °C; relative air humidity 60 ± 5%) under the light of light-emitting diodes (LEDs) consisting of 5% blue (B; 450 nm), 85% red (R; 660 nm), and 10% green (G; 530 nm) photosynthetic photon flux density (PPFD) at 200 µmol m−2 s−1 for 16 h d−1 (BRG, control) for 8, 15, and 25 days (BBCH 12, BBCH 14, and BBCH 18, respectively). For the EOD B treatments, lettuce plants were additionally illuminated with 100% of B light at 30 and 60 µmol m−2 s−1 PPFD for 4 h d−1 (B30 and B60, respectively). The results show that EOD B light caused the elevated shoot elongation of lettuce plants regardless of their growth stages. However, leaf width increased only in more developed lettuce plants (BBCH 18). EOD B light negatively affected the development of new leaves and fresh weight, except for seedlings (BBCH 12). Most photosynthetic and spectral leaf indices also decreased when lettuce was treated with EOD B light, especially under the PPFD level of 60 µmol m−2 s−1. Moreover, the changes in metabolic parameters such as DPPH free radical activity, free proline content, and H+-ATPase activity in lettuce showed a plant response to unfavorable conditions to EOD B light.

Influence of boron treatments on fatty acid desaturase metabolism in different safflower cultivars

This study investigated the expression levels of FAD2 genes important for the conversion of oleic acid to linoleic acid at cotyledon, root and leaf tissues of four different safflower cultivars (Olas, Remzibey, Dincer and Gokturk) subjected to B by qRT-PCR. Safflower species were grown in a controlled environmental growth chamber for 21 days and then exposed to different B concentrations ranging from 20 to 1 280 μmol for 24 h. RNA isolation, cDNA synthesis and RT-PCR analysis were performed on root, cotyledon and leaf tissues exposed to B stress for 24 h. It was determined that the expression levels of FAD2 genes decreased in the safflower cultivars exposed to increasing B concentrations. Under B stress conditions, the expression levels of FAD2 genes revealed an overall pattern of increase and reduction up to 160 μmol relative to the control group, and they reached the highest expression level. After 320 μmol, the activity of FAD2 genes was almost absent at increasing concentrations. All results show that the application of B causes significant changes in the expression of FAD2 genes and plays an important role in the defence mechanism against increased B toxicity.

The CO2 fertilization effect on leaf photosynthesis of maize (Zea mays L.) depends on growth temperatures with changes in leaf anatomy and soluble sugars

Understanding the potential mechanisms and processes of leaf photosynthesis in response to elevated CO2 concentration ([CO2]) and temperature is critical for estimating the impacts of climatic change on the growth and yield in crops such as maize (Zea mays L.), which is a widely cultivated C4 crop all over the world. We examined the combined effect of elevated [CO2] and temperature on plant growth, leaf photosynthesis, stomatal traits, and biochemical compositions of maize with six environmental growth chambers controlling two CO2 levels (400 and 800 μmol mol−1) and three temperature regimes (25/19°C, 31/25°C, and 37/31°C). We found that leaf photosynthesis was significantly enhanced by increasing growth temperature from 25/19°C to 31/25°C independent of [CO2]. However, leaf photosynthesis drastically declined when the growth temperature was continually increased to 37/31°C at both ambient CO2 concentration (400 μmol mol−1, a[CO2]) and elevated CO2 concentration (800 μmol mol−1, e[CO2]). Meanwhile, we also found strong CO2 fertilization effect on maize plants grown at the highest temperature (37/31°C), as evidenced by the higher leaf photosynthesis at e[CO2] than that at a[CO2], although leaf photosynthesis was similar between a[CO2] and e[CO2] under the other two temperature regimes of 25/19°C and 31/25°C. Furthermore, we also found that e[CO2] resulted in an increase in leaf soluble sugar, which was positively related with leaf photosynthesis under the high temperature regime of 37/31°C (R2 = 0.77). In addition, our results showed that e[CO2] substantially decreased leaf transpiration rates of maize plants, which might be partially attributed to the reduced stomatal openness as demonstrated by the declined stomatal width and stomatal area. These results suggest that the CO2 fertilization effect on plant growth and leaf photosynthesis of maize depends on growth temperatures through changing stomatal traits, leaf anatomy, and soluble sugar contents.

Phenotypic plasticity and nutritional quality of three kale cultivars (Brassica oleracea L. var. acephala) under field, greenhouse, and growth chamber environments

Comparative analysis of the physiological and biochemical characteristics of three kale cultivars (‘Toscano’, ‘Redbor’, and ‘Winterbor’) in different agricultural systems was performed. High biomass yield was observed in the plants grown in the field and greenhouse systems likely due to the higher light intensity (sunlight) and lower planting density during growth. The highest relative growth rate was observed in the field for ‘Redbor’ (104 mg g-1 d-1) and ‘Winterbor’ kale (115 mg g-1 d-1), while the highest growth rate for ‘Toscano’ kale was found in the greenhouse system (109 mg g-1 d-1). For all three cultivars, the smallest growth rate (72 – 78 mg g-1 d-1) and leaves with the highest specific-leaf area (295 – 378 cm2 g-1) were observed in the growth chamber environment. However, the highest concentration of phytochemicals (lutein, violaxanthin, chlorophyll a, and chlorophyll b) was detected in kale leaves from the growth chamber. The macular pigment, zeaxanthin, was detected in leaf samples harvested from the field and greenhouse grown kale primarily during high light conditions (PPFD > 1000 μmol m-2 s-1). Based on interaction study, cultivar type (genotype), growth stage at harvest, and farming system were identified as primary factors that determine nutritional quality in kale.

Fungal endophyte effects on invasive Phragmites australis performance in field and growth chamber environments

Manipulating plant microbiomes may provide control of invasive species. Invasive Phragmites australis has spread rapidly in North American wetlands, causing significant declines in native biodiversity. To test microbiome effects on host growth, we inoculated four common fungal endophytes into replicated Phragmites genotypes and monitored their growth in field and growth chamber environments. Inoculations were highly successful in the growth chamber but inoculated plants in the field were rapidly colonized by diverse endophytes from the local environment. There were significant genotype effects and minimal inoculation effects in both experiments with a significant inoculation × genotype interaction on tiller height in the field. Our results demonstrate that endophyte inoculation treatments are feasible, but repeated inoculations may be required to maintain high titer in plants subject to endophyte colonization from the local environment. Future studies should investigate a wider range of fungal endophytes to identify taxa that inhibit Phragmites and other invaders.

Temperature Effects on the Shoot and Root Growth, Development, and Biomass Accumulation of Corn (Zea mays L.)

Temperature is a critical environmental factor regulating plant growth and yield. Corn is a major agronomic crop produced globally over a vast geographic region, and highly variable climatic conditions occur spatially and temporally throughout these regions. Current literature lacks a comprehensive study comparing the effects of temperature on above versus below-ground growth and development and biomass partitioning of corn measured over time. An experiment was conducted to quantify the impact of temperature on corn’s early vegetative growth and development. Cardinal temperatures (Tmin, Topt, and Tmax) were estimated for different aspects of above- and below-ground growth processes. Plants were subjected to five differing day/night temperature treatments of 20/12, 25/17, 30/22, 35/27, and 40/32 °C using sun-lit controlled environment growth chambers for four weeks post-emergence. Corn plant height, leaves, leaf area, root length, surface area, volume, numbers of tips and forks, and plant component part dry weights were measured weekly. Cardinal temperatures were estimated, and the relationships between parameters and temperature within these cardinal limits were estimated using a modified beta function model. Cardinal temperature limits for whole plant dry weight production were 13.5 °C (Tmin), 30.5 °C (Topt), and 38 °C (Tmax). Biomass resources were prioritized to the root system at low temperatures and leaves at high temperatures. Root growth displayed the lowest optimum temperature compared to root development, shoot growth, and shoot development. The estimated cardinal temperatures and functional algorithms produced in this study, which include both above and below-ground aspects of plant growth, could be helpful to update crop models and could be beneficial to estimate corn growth under varying temperature conditions. These results could also be applicable when considering management decisions for maximizing field production and implementing emerging precision agriculture technology.

Profiling of Polyphenols and Glucosinolates in Kale and Broccoli Microgreens Grown under Chamber and Windowsill Conditions by Ultrahigh-Performance Liquid Chromatography High-Resolution Mass Spectrometry

Vegetables from the Brassica family are rich in many health-beneficial components, including high levels of polyphenols and glucosinolates (GSLs). However, their exact metabolite compositions are highly affected by cultivating and environmental conditions. Here, we provide the first report of polyphenol and GSL composition of kale and broccoli microgreens grown in growth chamber and windowsill environments. The samples were harvested 10 days after sowing and analyzed using ultrahigh-performance liquid chromatography high-resolution mass spectrometry. Principal component analysis was performed to visualize group clustering, trends, and discriminative ion features. Flavonol derivatives (21 in kale and 7 in broccoli) and hydroxycinnamic acid derivatives (14 in kale and 22 in broccoli) were identified under both growing conditions. Additionally, GSLs, including 7 in kale and 9 in broccoli, were detected. The results demonstrated a clear variation in secondary metabolites between the two growing conditions. The discriminative ion features were hydroxycinnamic acid esters of flavonols and indolic GSLs. Compared to chamber conditions, hydroxycinnamic acid esters of flavonols such as kaempferol-3-disinapoyl-triglucoside-7-diglucoside, kaempferol-3-disinpapoyl-triglucoside-7-glucoside, and kaempferol-3-disinpapoyl-diglucoside-7-glucoside were found to be greater in the windowsill-grown vegetables. The contents of 4-methoxyglucobrassicin and neoglucobrassicin, on the other hand, were greater in the chamber-grown ones. The results suggest that kale and broccoli microgreens grown under commercial- and in-home-grown conditions have different secondary metabolite compositions.