Manganese nutrition and photosynthesis in NAD-malic enzyme C-4 plants

Title from PDF of title page (University of Missouri--Columbia, viewed on February 24, 2010).The entire thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file; a non-technical public abstract appears in the public.pdf file.Dissertation advisor: Dr. Dale Blevins.Vita.Ph.D. University of Missouri--Columbia 2008.Based on their photosynthetic pathways, plants can be divided into three major groups: C-3, CAM, and C-4. In C-4 plants, the release of CO2 for Calvin cycle reactions in bundle sheath cells (BSC) involves one of the three principal enzymes: NADP-malic enzyme (NADP-ME), PEP-carboxykinase enzyme (PEPCK), and NAD-malic enzymes (NAD-ME). Of these three decarboxylating enzymes, only the activation of NAD-ME has an absolute requirement for Mn, therefore, leaf Mn concentrations could be critical for maximum NAD-ME activity and the continued supply of CO2 to bundle sheath cells. The objective of this research was to determine the Mn requirement for optimum photosynthesis and plant biomass production for two agriculturally important NAD-ME C-4 species, pearl millet (Pennisetum glaucum L. R. Br) and purple amaranth (Amaranthus hypochondriacus L.). These species were examined in parallel with two NADPME (no Mn activation required) species, corn (Zea mays L.) and sorghum (Sorghum bicolor L. Moench), and two C-3 species, wheat (Triticum aestivum L. cv. Ernie) and squash (Cucurbita pepo L. cv. straighneck) added as controls. Plants were grown in a complete nutrient solution with Mn concentrations ranging xiii from 0 to 100 [mu]M. Field grown pearl millet and purple amaranth received Mn from two sources, Mn beads and manganese chloride. Manganese concentration required for optimum photosynthetic rate and biomass production of the C-3 and NADP-ME C-4 species was found to be [about]2 [mu]M, which is the concentration commonly used in plant nutrient media. Manganese concentrations above 2 [mu]M had no significant effect on either photosynthetic rate or biomass production of these plants. Also, in C-3 and NADP-ME C-4 species, light saturated photosynthesis (Amax) was the highest for plants receiving 2-5 [mu]M Mn and no change was observed with increasing Mn concentration. In contrast, in both NAD-ME species, the optimum growth and photosynthetic responses required Mn concentrations 20-fold higher than those typically used in hydroponic media, and increasing Mn concentration from 10 to 75 [mu]M resulted in a 50% increase in photosynthetic rate in purple amaranth and a 36% increase in pearl millet. NAD-ME plants receiving higher Mn concentrations had greater responses to increasing photosynthetic photon flux density (PPFD), and at saturating light, pearl millet and purple amaranth receiving [greater than or less than]50 [mu]M Mn achieved higher Amax than those receiving lower Mn treatments. However, in all plant species, Mn treatment had little effect on the apparent quantum yield (AQY), perhaps indicating that at this range, light rather than Mn was limiting photosynthesis. Interestingly, Mn concentration higher than 2 [mu]M had little effect on stomatal conductance in all six tested species. This strongly implies that increased photosynthetic rates in NAD-ME species with higher Mn nutrition was a result of a better internal supply/utilization of CO2 and not of an improved stomatal conductance. In field experiments, Mn fertilization resulted in slightly increased leaf Mn concentrations and an up to [about]20% increase in photosynthetic rate. In general, Mn fertilization had little effect on seed mineral element composition or seed protein and oil content, but resulted in a slight increase in seed yield. This is, to my knowledge, the first information on the substantial, 20-fold higher Mn requirement for optimum photosynthesis and biomass production of NAD-ME C-4 plants, compared to other plant species. This finding should be considered in future research on NAD-ME C-4 crops, especially under soil conditions that decrease Mn availability for plant uptake. As more information is collected on NAD-ME C-4 plant biochemistry, physiology, and structure, more specific recommendations for nutrient requirements and more specific Mn application strategies can be developed.Includes bibliographical reference

Effect of Priming and Seed Size on Germination and Emergence of Six Food-Type Soybean Varieties

Soybean (Glycine max (L.) Merr.), a good source of protein and oil, is used to produce nutritious isoflavone-rich soybean-based foods. The objectives of this study were (i) to determine the germination difference among soybean seeds in various seed sizes and (ii) to evaluate effects of seed pretreatment on germination and seedling emergence. Six varieties of different seed size class were used: (i) small size (MFS-561 and V08-4773), (ii) medium size (Glen and V03-47050), and (iii) large size (MFL-159 and V07-1897). Pregermination treatments include 0, 5, or 10 hours soaking and germinating/planting with or without nitrogen fertilizer. Large seed size varieties showed low germination rate and N addition caused the least reduction in germination in these seeds during the first 24 hours. While N had no effect on seed germination after 72 hours, growth in N treated seed was low. Seedling emergence was comparable across varieties in 2013 and water priming and N application had no effect. However, while varieties did not differ in final emergence for nonprimed seeds in 2014, water priming led to a high reduction in seedling emergence of large seed varieties in this study. Application of N fertilizer had no effect on seedling emergence in field experiments

Managing Nitrogen and Phosphorus Nutrients for Switchgrass Produced for Bioenergy Feedstock in Phosphorus-Deficient Soil

There is limited information available explaining the agronomic and economic relationships between yield and nitrogen and phosphorus applications to growing switchgrass produced in phosphorus-deficient soils. The objective of this study was to determine the effects of nitrogen and phosphorus fertilizers on feedstock yield and measures of expected total cost, gross revenue, net return, and breakeven price of feedstock produced in phosphorus-deficient soils in the southern Great Plains. Data were collected from a three-year, two-location agronomic field study conducted in south-central Oklahoma. Two discrete nitrogen treatments (0 and 134 kg ha-1) and four discrete phosphorus treatments (0, 30, 60 and 90 kg ha-1) were randomly assigned to small plots arranged in a randomized complete block designed (RCBD) study. Random effects mixed ANOVA models were used to estimate the effects of nitrogen, phosphorus and nitrogen by phosphorus interactions on feedstock yield and the economic variables specified. Results showed that, on average over site-years, switchgrass yield increases from 10.5 to 12.3 Mg ha-1 with the highest (101-kg ha-1) treatment; however, we found no statistical difference in net profitability between phosphorus treatments. Yield and net return did respond significantly to 135 kg-1 of N ha-1. Our results suggest that phosphorus-deficient soils do not seem to have the same impact on switchgrass yield and profitability as they do for the yields and profitability of other crops traditionally grown in this region.bioenergy feedstock, economics, phosphorus-deficient soils, nitrogen, switchgrass, Crop Production/Industries, Environmental Economics and Policy, Production Economics,

Economic Potential of Substituting Legumes for Synthetic Nitrogen in Warm Season Perennial Grasses used for Stocker Cattle Grazing

Stocker cattle grazing warm season perennial grasses is an important economic activity in the southern Great Plains. Substantial increases in the price of nitrogen fertilizer is negatively affecting forage producers’ profitability. Two alternative nitrogen management systems that use annual and perennial legumes have been developed for bermudagrass pastures. The goal of the study is to determine if the legumes systems are more profitable than the conventional practice of applying synthetic sources of nitrogen. Results of the two-year grazing study show that the legume systems could not compete economically with the common practice.economics, grazing, legumes, bermudagrass, nitrogen fertilizer, stocker cattle, Crop Production/Industries, Farm Management, Production Economics,

Root and Inorganic N Distribution in a Soil Profile: Cropped Versus Non-Cropped Fields

Tree legume fallows capture and ‘pump-up’ leached nitrate and recycle N through leaf litter. This study compared subsoil nitrate under continuous maize (Zea mays), natural weed fallow, sesbania (Sesbania sesban) fallow and bare fallow. Results showed that across systems, NO3-N in the top 30 cm ranged from 6.9 to 11 kg N ha-1. While NO3-N increased to 28 kg ha-1 in maize and 86 kg ha-1 in bare fallow at 50-100 cm, it remained below 10 kg N ha-1 in sesbania and weed fallow. Ammonium N ranged between 1-5 kg N ha-1 at 0-50 cm and between 5-10 kg N ha-1 at lower depths in all LUS. At the topsoil (0-30 cm), weed fallow had higher root length density of 32,000 m m-3 compared to 5,970 m m-3 in maize and 15,800 m m-3 in sesbania. Root length density at 105-150 cm was 958, 1746, and 1479 m m-3 in maize, weed, and sesbania, respectively. The root biomass to 150 cm was 10.9 tonnes ha-1 in sesbania, 0.91 tonnes ha-1 in weeds and 0.78 tonnes ha-1 in maize. Shoot P content ranged from 7-11 kg ha-1 for all LUS, while 248 kg N ha-1 in sesbania shoots was 3-fold and 5-fold higher than continuous maize and weed fallow. Compared to continuous maize and weed fallows, sesbania reduced subsoil nitrate. Incorporating deep rooting plants into the cropping system can substantially reduce subsoil nitrate, and the N contribution by legumes would be greater than that of weed biomass or maize stover

Effects of Media Ph on Growth and Nutrient Content of Two Grape Cultivars

The study involved two grape cultivars, Vidal blanc and Norton, growing in pots with amended media of pH 4.5, 5.9, 7.2, or 8.5. The two factor experiment was set up in a randomized complete block design with six replications. The objectives were to determine vegetative growth and nutrient content of these cultivars as affected by media pH and to determine the optimum pH range within those tested for cultivar growth. Vidal blanc was superior to Norton in all growth measurements. Raising media pH from 5.9 to 7.2 and 8.5 led to significant reductions in shoot length, specific leaf weight, leaf and shoot dry weight, and an increase in root to shoot ratio for Norton but not for Vidal blanc. For Norton, a comparatively higher reduction in shoot than root growth was responsible for increased root to shoot ratio above 7.0. Cultivars had similar levels of K, Fe, and Cu, but Norton had higher P, Ca, B, and A1 and lower Mg than Vidal blanc. Increasing media pH led to lower P, Mg, Mn and higher B in both cultivars. Unlike Vidal blanc, Norton showed noticeable Fe, Mn and Mg deficiency symptoms at media pH above 7.0 despite having higher content than Vidal blanc. This most likely indicates poor utilization rather than a deficiency of these nutrients for Norton. The range 5.9 to 7.2 and 7.2 to 8.5 appears to encompass the optimum pH for growth of Norton and Vidal blanc respectively

Root and Inorganic N Distribution in a Soil Profile: Cropped Versus Non-Cropped Fields

Tree legume fallows capture and ‘pump-up’ leached nitrate and recycle N through leaf litter. This study compared subsoil nitrate under continuous maize (Zea mays), natural weed fallow, sesbania (Sesbania sesban) fallow and bare fallow. Results showed that across systems, NO3-N in the top 30 cm ranged from 6.9 to 11 kg N ha-1. While NO3-N increased to 28 kg ha-1 in maize and 86 kg ha-1 in bare fallow at 50-100 cm, it remained below 10 kg N ha-1 in sesbania and weed fallow. Ammonium N ranged between 1-5 kg N ha-1 at 0-50 cm and between 5-10 kg N ha-1 at lower depths in all LUS. At the topsoil (0-30 cm), weed fallow had higher root length density of 32,000 m m-3 compared to 5,970 m m-3 in maize and 15,800 m m-3 in sesbania. Root length density at 105-150 cm was 958, 1746, and 1479 m m-3 in maize, weed, and sesbania, respectively. The root biomass to 150 cm was 10.9 tonnes ha-1 in sesbania, 0.91 tonnes ha-1 in weeds and 0.78 tonnes ha-1 in maize. Shoot P content ranged from 7-11 kg ha-1 for all LUS, while 248 kg N ha-1 in sesbania shoots was 3-fold and 5-fold higher than continuous maize and weed fallow. Compared to continuous maize and weed fallows, sesbania reduced subsoil nitrate. Incorporating deep rooting plants into the cropping system can substantially reduce subsoil nitrate, and the N contribution by legumes would be greater than that of weed biomass or maize stover

Effect of Nitrogen Fertilizer Rate and Harvest Season on Forage Yield, Quality, and Macronutrient Concentrations in Midland Bermuda grass

Bermuda grass [Cynodon dactylon (L.) Pers.] is a major forage for grazing and hay production in the southern United States. The objectives of this study were to determine effects of nitrogen (N) fertilization rate (0, 112, 224, 336, and 448 kg ha−1), split spring and summer applications of N at the 224 and 448 kg ha−1 rates, and harvest periods (spring and summer) on forage yield, crude protein (CP), acid detergent fiber (ADF), neutral detergent fiber (NDF), total digestible nutrients (TDN), and concentrations of phosphorus (P), potassium (K), magnesium (Mg), and calcium (Ca) in Midland Bermuda grass. Data were collected from 2002 to 2008 as part of an ongoing, long-term soil fertility experiment in southern Oklahoma. Repeated measures analysis of these long-term data showed that forage yield responses to N rate varied with year and harvest time with up to 2.5-fold yield differences among years. Nitrogen fertilization increased CP, TDN, and macronutrient P and Mg and decreased ADF and NDF. Crude protein was increased by ≥50%, and ADF and NDF dropped by up to 25% with the greatest N rate. In general, split N applications did not affect forage yield but produced low-quality forage compared to single N application in spring. Split application of 448 kg N ha−1 gave forage with CP, TDN, ADF, and NDF similar to the Bermuda grass receiving 336 or 448 kg N ha−1 as a single application. Spring forage had better forage quality than summer harvests. While N fertilization increased forage Mg and P concentrations by more than 50% during both spring and summer, it had no effect or slight increased K and Ca concentrations. In the southern Great Plains, despite the weather-dependent variability in forage yield of Bermuda grass, N application increase forage quality

Studies on oriental fruit moth (Lepidoptera: Tortricidae) pheromone microcapsules using various tree fruit species, cultivars, and application methods

The number of microcapsules containing pheromone of the oriental fruit moth, Grapholita molesta (Busck), was determined on leaves from apple, Asian and European pear, peach, sweet and tart cherry, and plum trees. In addition, we compared the number of microcapsules on apple and peach leaves using a laboratory leaf dip application and a field airblast sprayer application. Finally, we compared the number of microcapsules on two apple and peach cultivars after airblast sprayer applications of microencapsulated pheromone. The bottom surface of \u27Gala\u27 apple leaves had microcapsule density of 0.47, the highest among the different tree fruits. The bottoms of \u27Shinko\u27 Asian pear had the lowest microcapsule density of 0.09 followed by the tops of \u27Bluebell\u27 plum and \u27Columbia\u27 sweet cherry leaves both with density of 0.10. The greater than 3-fold difference between the fruit leaves with the highest and lowest numbers of microcapsules may indicate the need for rate specific recommendations on different species of fruit trees. The number of microcapsules on apple and peach leaves treated with laboratory leaf dips was 8- to 60-fold greater than the number of microcapsules on field-treated leaves. Although laboratory treatments eliminated other potentially confounding field variables, they did not accurately represent microcapsule numbers on leaves treated with an airblast sprayer. There were significant differences in microcapsule abundance on \u27Delicious\u27 and \u27Gala\u27 apple leaves and \u27Encore\u27 and \u27Red Haven\u27 peach leaves. Trichome abundance and cuticle structure may be responsible for the differences in the number of microcapsules on various tree fruit species and cultivars