Physical Sciences and Mathematics Commons^™

Photosynthesis And Water Relations Of Two Savanna Grasses As Influenced By Shade And Water Stress, M J. Trlica, J I. Kinyamario

IGC Proceedings (1993-2023)

Net CO2 assimilation and plant water relations of the African savanna grasses Panicum maximum Jacq. and Tliemeda triandra Porrsk. were measured under controlled conditions. We hypothesised that 1; triandra would be better adapted to higher light and temperature conditions and could withstand greater moisture stress than could P. maximum, as T. tria11dra is commonly found in open areas, whereas P. maximum dominates in the shade of trees. Plants of both species were transplanted into a common soil in large pots and placed under shade (approximately 150 µrnoVm1/s photon flux density (PFD)) or high light (approximately 1200 µmoVm1/s PFD) conditions, with …

Climate Change And Grasslands: Ecosystem-Level Responses To Elevated Carbon Dioxide, Clenton E. Owensby

IGC Proceedings (1993-2023)

Elevated CO2 is the major greenhouse gas associated with global climate change. The impact of increasing atmospheric CO2 on grassland ecosystems has been studied little. Studies with single plants or populations in controlled environments have provided knowledge of the mechanisms involved in plant response to elevated CO21 but without ecosystem-level studies over an extended period, we will be unable to make any valid predictions. Primary production of grassland ecosystems under elevated CO2 will likely increase, with the greatest increase coming with C3-dominated plant communities, or plant communities that are .subjected to frequent drought stress. Increased nitrogen-use efficiency and reduced nitrogen …

Photosynthesis And Water Relations Of A C4 And A C3 Grass Under Doubled Carbon Dioxide, D Nie, M B. Kirkham, E T. Kanemasu

IGC Proceedings (1993-2023)

The objective of this project was to determine during an entire season the photosynthetic rate and water potential of a C3 grass (Kentucky bluegrass, Poa pratensis L.) and a C4 grass (big bluestem, Andropogon gerardii Vitman) grown with 2 levels of CO2 (ambient or twice ambient) and 2 water levels (field capacity or no water added). Elevated CO2 increased the photosynthetic rate of Kentucky bluegrass by an average of 76%. During mid-season (11 June-16 July), photosynthetic rate of high-water big bluestem with ambient CO2 was about the same as that of low-water big bluestem with doubled CO2• Under both water …

Whole-Stand Carbon Gains And Nitrogen Distribution In Herbaceous Stands, M.J A. Werger, T Hirose

IGC Proceedings (1993-2023)

We studied canopy structure and leaf nitrogen distribution in open and dense stands of tall dicot and monocot herbs and compared the results with simulated canopy performance under uniform and optimised leaf nitrogen distributions. Dense stands showed leaf nitrogen distributions that greatly differed from those of uniform distribution but did not completely match optimum distribution. In dense stands this led to strongly enhanced potential whole canopy carbon gains, while in open stands the leaf nitrogen distribution was not very important in this respect. Dense stands of monocots kept more leaf nitrogen in the lower parts of their canopies than is …

Effects Of Water Deficit On Osmotic Adjustment And Photosynthesis Of Miscanthus Spp. Collected From Different Rainfall Regions, J Weng

IGC Proceedings (1993-2023)

Four entries of Miscanthus spp., collected from different rainfall regions, were transplanted in pots. They were subjected to S drying cycles; each cycle lasted 6-7 days. Leaf photosynthesis (Pn) began to decline when leaf water potential (L) declined to •l.3 to -1.S MPa; the L values at SO% Pn (½Pn) were -1.6 to -2.6 MPa, The L (1hPn) values were lower in plants collected from northern Taiwan (highly frequent rainfall) than those collected from southern Taiwan (distinct wet and dry season). Further, the L (½Pn) value became lower in all the entries when drying cycle was advanced, with northern Taiwan …

Some Ecological Aspects Of Semi-Natural And Temporary Grasslands, N Gaborcik, L Ondrasek, J Cunderlik, J Tomaskin, T Kizek

IGC Proceedings (1993-2023)

Some ecological aspects were studied in semi-natural and temporary grasslands at different levels of fertilizer application. The research was carried out in the upland region of central Slovakia at the altitude of 460 m in Banská Bystrica. At zero fertilizer application, soil CO2 production and Cox content were higher in the temporary grassland. Atmospheric N fixation was also higher in the temporary grassland. However, root accumulation, microbial biomass content and R : S ratio were lower in the temporary grassland. By comparison with the semi-natural grassland, leaf area index (LAI), net assimilation rate (NAR) and crop growth rate (CGR) were …

Growth And Physiology Respond Differently To Elevated Co2 In Nad-Me And Nadp-Me C4 Grasses, D R. Lecain, J A. Morgan

IGC Proceedings (1993-2023)

Plants with C4 photosynthesis have one of three decarboxylation enzymes in their bundle sheath cells. Reports suggest that bundle sheath leakiness to CO2 is highest in the NAD-ME group, lowest in the NADP-ME group and intermediate in the PCK group. We investigated the hypothesis that growth and photosynthesis of three NADME grasses would respond more to elevated CO2 than three NADPME grasses. Contrary to our hypothesis, growth of NADP-ME grasses was greater under elevated CO2, while none of the NADME grasses had a significant response. Increased leaf non-structural carbohydrates were associated with greater growth responses of NADP-ME grasses, while none …

Morphological And Physiological Response Of Planeleaf Willow (Salix Planifolia Pursh.) To Simulated Browsing, L Xu, J L. Dodd, M A. Smith, Q D. Skinner, W A. Laycock

IGC Proceedings (1993-2023)

Morphological and physiological responses of planeleaf willow (Salix planefolia Pursh.) to simulated browsing were studied under controlled conditions. The treatments consisted of every combination of three clipping intensities (30%, 60% and 90% of current twigs length removal) and three clipping timings (late winter, early spring and mid-summer). Increased clipping intensity stimulated bud activation; increased total leaf area and leaf size and increased the length of current year’s twigs. Mid-summer browsing increased the total number of leaves, the number of current twigs and decreased the length of current twigs. Higher browsing intensity resulted in higher photosynthetic rate of recently matured …

Dormant-Season Carbon Fluxes In Humid-Temperate Pastures, Howard Skinner

IGC Proceedings (1993-2023)

Human induced increases in atmospheric CO₂ through the burning of fossil fuels and deforestation are considered to be a primary cause of rising global temperatures. However, carbon sequestration by terrestrial ecosystems has reduced the rate of CO₂ accumulation in the atmosphere. Because of their vast size, grazing lands have the potential to sequester significant quantities of carbon, slowing the increase in atmospheric CO₂ and reducing the risk of global warming. Although C uptake during the growing season can be substantial, losses following defoliation and drought, and during the winter months can significantly reduce annual sequestration, frequently turning …

Net Photosynthesis Rate And Chlorophyll Content Of Caucasian And White Clover Leaves Under Different Temperature Regimes, A. D. Black, R. J. Lucas, D. J. Moot

IGC Proceedings (1993-2023)

In spring and summer in intensive temperate pastures, Caucasian clover (Cc) (Trifolium ambiguum) has higher dry matter (DM) production rates than white clover (wc) (Trifolium repens) (Black et al., 2003). An examination of the physiological basis for these differences can provide a greater insight into the suitability of Cc for inclusion in temperate pastures. Specifically, leaf photosynthesis rate is a major driver of seasonal growth and is strongly regulated by temperature and chlorophyll content. This study aimed to compare the net photosynthesis rate (Pn) and chlorophyll content of Cc and wc leaves under different temperature …

Identifying Genes Influencing The Efficiency Of Photosynthesis, Jason M. Rivera, Steven Burgess

PRECS student projects

• Photosynthesis adapts to environmental conditions over time.¹

• Varying environmental conditions lead to stress accumulation on the plant.²

• A genetic library has been assembled for forward genetic screening of Arabidopsis thaliana.³

• Arabidopsis Thaliana is a model plant used as a model organism in growth experiments.

• This research project aims to identify and analyze candidate genes that impact the efficiency of photosynthesis.

• These genes can be transplanted into commercial crops to increase efficiency of photosynthesis and crop yields.

Photorespiration In Eelgrass (Zostera Marina L.): A Photoprotection Mechanism For Survival In A Co₂-Limited World, Billur Celebi-Ergin, Richard C. Zimmerman, Victoria J. Hill

OES Faculty Publications

Photorespiration, commonly viewed as a loss in photosynthetic productivity of C3 plants, is expected to decline with increasing atmospheric CO₂, even though photorespiration plays an important role in the oxidative stress responses. This study aimed to quantify the role of photorespiration and alternative photoprotection mechanisms in Zostera marina L. (eelgrass), a carbon-limited marine C3 plant, in response to ocean acidification. Plants were grown in controlled outdoor aquaria at different [CO₂]aq ranging from ~55 (ambient) to ~2121 μM for 13 months and compared for differences in leaf photochemistry by simultaneous measurements of O₂ flux and …

High-Resolution Cryo-Electron Microscopy Structure Of Photosystem Ii From The Mesophilic Cyanobacterium, Synechocystis Sp. Pcc 6803, Christopher J. Gisriel, Jimin Wang, Jinchan Liu, David A. Flesher, Krystle M. Reiss, Hao-Li Huang, Ke R. Yang, William H. Armstrong, M. R. Gunner, Victor S. Batista, Richard J. Debus, Gary W. Brudvig

Publications and Research

Photosystem II (PSII) enables global-scale, light-driven water oxidation. Genetic manipulation of PSII from the mesophilic cyanobacterium Synechocystis sp. PCC 6803 has provided insights into the mechanism of water oxidation; however, the lack of a highresolution structure of oxygen-evolving PSII from this organism has limited the interpretation of biophysical data to models based on structures of thermophilic cyanobacterial PSII. Here, we report the cryo-electron microscopy structure of PSII from Synechocystis sp. PCC 6803 at 1.93-Å resolution. A number of differences are observed relative to thermophilic PSII structures, including the following: the extrinsic subunit PsbQ is maintained, the C terminus of the …

High Salinity Effects On The Components Of Relative Growth Rate In Rhodes Grass, E. Taleisnik, L. García Seffino, A. Córdoba, K. Grunberg, C. Arias, M. De Luca

IGC Proceedings (1993-2023)

Rhodes grass (Chloris gayana Kunth), is widely cultivated in the semiarid tropics and favored for its salt tolerance. Nevertheless, productivity decreases significantly under saline conditions, especially in tetraploid cultivars. The purpose of this work was to explore, in tetraploid cultivar Boma, the physiological causes for the observed salt-associated growth reduction. The effects of high salinity (200 mM NaCl) on the components of relative growth rate were analyzed in greenhouse experiments. An early reduction in leaf area expansion was observed, which later resulted in decreased dry matter accumulation. Plant leafiness was reduced by effects both on dry matter allocation to …

Photosynthetic Light Response Of Tanzania Grass Under Four Levels Of Leaf Temperature, A. C. L. De Mello, P. M. Santos, Carlos G. S. Pedreira, M. Corsi, C. T. Dos S. Dias

IGC Proceedings (1993-2023)

The purpose of this paper is to establish photosynthetic light response curves for Tanzania grass (Panicum maximum Jacq.) under four leaf temperature levels. Photosynthetic rate was measured as a response to levels of photosynthetic photon flux density (PPFD) on the youngest fully expanded leaves of 12 representative tillers with an infra red gas analyzer. The effect of PPFD was tested for each leaf temperature level in a randomized complete block design. Photosynthetic light response curves were adjusted for each leaf temperature using a non-linear hyperbolic model. The maximum photosynthetic response was 25,59; 31,43; 34,57 and 27,53 µmol CO_{2 …}

Effect Of The Hierarchical Position Of Individuals In A Medicago Sativa Stand On Shoot Respiration, M. Lötscher, Hans Schnyder

IGC Proceedings (1993-2023)

The influence of the hierarchical position on the relationship between C gains and C losses (respiration) of individuals was investigated in a alfalfa (Medicago sativa) stand. The hierarchical position that an individual occupied was defined by its height relative to the stand height. Stands were established by arranging potted individual plants at a density of 400 plants m^-2. Stands were grown in growth cabinets. ¹³C steady-state labelling was used to assess C fixation (C_new) by individuals during a photoperiod of 16 h. Respiration of shoots was measured during the following 8 h dark …

Salinity Effects On Plant Growth, Photosynthesis, And Ion Content Of Covered And Naked Oat, Guiqin Zhao, Baoluo Ma

IGC Proceedings (1993-2023)

No abstract provided.

Using The Marcus Inverted Region And Artificial Cofactors To Create A Charge Separated State In De Novo Designed Proteins, Eskil Me Andersen

Dissertations, Theses, and Capstone Projects

To create an efficient de novo photosynthetic protein it is important to create long lived charge separated states. Achieving stable charge separation leads to an increase in the efficiency of the photosynthetic reaction which in turn leads to higher yields of end products, such as biofuels, electrical charge, or synthetic chemicals. In an attempt to create charge separated states in de novo proteins we hypothesized that we could engineer the free energy gaps in the proteins from excited primary donor (PD) to acceptor (A), and A back to ground state PD such that the forward electron transfer (ET) would be …

Does The Short Term Fluctuation Of Mineral Element Concentrations In The Closed Hydroponic Experimental Facilities Affect The Mineral Concentrations In Cucumber Plants Exposed To Elevated Co2?, Xun Li, Jinlong Dong, Nazim Gruda, Wenying Chu, Zengqiang Duan

Chemistry & Biochemistry Faculty Publications

Aims

Studies dealing with plants’ mineral nutrient status under elevated atmospheric CO₂concentration (eCO₂) are usually conducted in closed hydroponic systems, in which nutrient solutions are entirely renewed every several days. Here, we investigated the contribution of the fluctuation of concentrations of N ([N]), P ([P]), and K ([K]) in nutrient solutions in this short period on their concentrations in cucumber plants exposed to different [CO₂] and N levels.

Methods

Cucumber (Cucumis sativus L.) plants were hydroponically grown under two [CO₂] and three N levels. [N], [P], and [K] in nutrient solutions …

How Wetland Plants Deal With Stress, Taylor M. Sloey

Biological Sciences Faculty Publications

We all get stressed. To deal with that stress, some of us may exercise, take a bubble bath, cry, or simply leave the stressful situation. But how can you cope with stress if you are rooted in place? Plants that live in estuaries are exposed to many types of stresses from the environment, including flooding, high salt levels, low soil oxygen, and waves. Fortunately, wetland plants have developed ways to survive within these conditions, from excreting salt, to growing faster, to even breaking down cell walls to maximize air flow. Plants can tolerate different levels of stress depending on their …

Carbon Balance In Stand Of An Annual Herb At An Elevated Co2 Concentration, Almaz Borjigidai, Kouki Hikosaka, Tadaki Hirose

IGC Proceedings (1993-2023)

No abstract provided.

Effect Of Grazing Intensity On Photosynthesis And Soil Respiration Of Alpine Grassland In Tibet, Y. F. Wan, Q. Z. Gao, Y. Li, X. B. Qin, W. Z. Jiancun, B. S. Wang

IGC Proceedings (1993-2023)

No abstract provided.

Effect Of Gradually Water Stress And Recovery On Photosynthesis, Transpiration, And Stomatal Conductance In Two Plantago Species, A. Rahimi, H. R. Rahimian Mashhadi, M. R. Jahansoz

IGC Proceedings (1993-2023)

No abstract provided.

Changes Of Residue Function And Signaling Regrowth After Forage Cutting, Huimin Yang, Linag Zhao, Yuying Shen, Xiaoyan Zhang

IGC Proceedings (1993-2023)

No abstract provided.

Changes Of Cap Of Creeping Bentgrass As Affected By Light Intensity During Summer Stress, Zhiming Yang, Zhihua Li

IGC Proceedings (1993-2023)

No abstract provided.

Photosynthesis And Transpiration Of Chicory With Different Irrigation Treatments In Beijing, Lin Meng, Yingjun Zhang, Peichun Mao, Guofang Zhang

IGC Proceedings (1993-2023)

No abstract provided.

Responses Of Photosynthetic Rate Of Lucerne And The Mechanisms Under Cutting At Different Water Availabilities, Shubin He, Huimin Yang, Guoli Liu, Zhilong Zhang

IGC Proceedings (1993-2023)

No abstract provided.

The Study On The Photosynthetic Characteristics Of Three Melilotoides Ruthenica Strains, Lili Zhao, Zhaolan Wang, Qingfeng Li, Jiancai Du, Xiaotao Mao

IGC Proceedings (1993-2023)

No abstract provided.

Can Desert Mosses Hide From Climate Change? The Ecophysiological Importance Of Habitat Buffering & Water Relations To A Keystone Biocrust Moss In The Mojave Desert, Theresa Ann Clark

UNLV Theses, Dissertations, Professional Papers, and Capstones

Empirical and observational studies suggest a keystone biocrust moss, Syntrichia caninervis, may be sensitive to future climate change in the American Southwest due to its uniquely sensitive water relations that appear particularly challenged during summer hydration-desiccation cycles. However, the potential mitigating roles of habitat buffering, acclimatization, and winter recovery on the vulnerability of this species remain largely unexplored. I investigated potential abiotic and biotic resiliency factors driving summer stress resistance and recovery in S. caninervis along present-day aridity gradients in the Mojave Desert to strengthen the climate change vulnerability assessment for this species common to biocrusts of North America, northern …

Alteration Of Physiological Parameters Of Milkvetch (Astragalus Adsurgens) By The Pathogen Embellisia Astragali, Binhua Yu, Zhibiao Nan

IGC Proceedings (1993-2023)

Milkvetch (Astragalus adsurgens) is sown on > 1 M ha in China as a forage legume and to control soil and water erosion. It is drought-tolerant and has high herbage yield, wide adaptability and medium forage quality. However, fungal disease is a major factor affecting its persistence and productivity. Embellisia astragali is a highly virulent seed-borne pathogen which commonly causes stunt and root rot. The objective of this study was to characterize the impact of Embellisia astragali on the physiological status of milkvetch by monitoring changes through time in net photosynthesis, stomatal conductance and other parameters of milkvetch inoculated …