July 2012 Botanical Society of America Meeting
I have organized a symposium and presented at the 2012 Botanical Society of America Meeting, July 9th in Columbus, Ohio.
- My students also participated & Robert Griffin-Nolan wins the prestigous Licor Prize!
DRUM ROLL PLEASE...
MY STUDENT, ROBERT GRIFFIN-NOLAN WINS THE LICOR PRIZE!
FOR HIS AWESOME POSTER PRESENTATION - WAY TO GO BERTO!
Robert Griffin-Nolan* (biology student), Rosen, Benjamin* (biology alumni), Melcher, Peter (biology faculty). BSA 2012
The role of green light in photosynthesis in Bryophytes and higher plants.
The focus of this study was to analyze photosynthetic responses of bryophytes and higher plants. For the Bryophytes we measured these responses when they were grown under a spectrum of green light (peak 523 ± 20 nm) and white light treatments. We studied the response of three bryophyte species (Dicranum spp., Sphagnum spp., and Hypnum spp.) to three light treatments: 20 μmol m-2 s-1 full-spectrum light, 20 μmol m-2 s-1 green light (λmax = 520 nm) and 100 μmol m-2 s-1 full spectrum light all at 20 oC. We found that Bryophytes have photosynthetic plasticity in response to the light treatments with responses being species dependent. For example, Dicranum spp. showed enhanced dark-adapted photosynthetic efficiency (Fv/Fm) in response to light level and to light quality (ANOVA, P = 0.002; PS II efficiency determined using a Fluorescence imaging system - cf imager by Technologia™, UK). Assessment of the capacity of tropical and temperate higher plants to use green light in photosynthesis was achieved by measuring photosynthetic responses of plants exposed to variation in light quality and quantity using a Licor-6400 XT. Photosynthetic responses varied greatly in higher plants and were both species dependent and dependent on variation in growing conditions (shade versus sun adapted plants) with shade adapted plants having higher quantum efficiencies in response to green light compared to full-sun adapted plants. The mechanism used by plants to use green light to effectively power photosynthesis in these shade adapted plants is still unclear and under investigation. However, we hypothesize that carotenoids and other xanthophylls and possible protein associates are playing a major role in this process.
MY STUDENT LEANNE DONAHUE ALSO PRESENTED A SMASHING POSTER ON A NEW SCREENING METHOD USING FLUORESCENCE IMAGING (HER POSTER ROCKED!)
Donahue, Leanne*, Griffin-Nolan, Robert*, Hamilton, Jason, Melcher, Peter.
A rapid fluorescence imaging screening protocol to assess PSII electron efficiency of plants. BSA 2012
Plants have both direct and indirect defense traits in response to changes in both abiotic (mechanical,UV, water and/or temperature stress) and biotic (herbivore attack, plant-plant interactions) stressors. For example, plants can elicit direct defenses to reduce the susceptibility of attacking insects and in response to changes in abiotic conditions that result in increased plant fitness. Plants also have indirect defenses, such as the production of volatile organic compounds that can facilitate top-down control of herbivore populations by increasing the foraging success of herbivore predators and parasitoids. Abiotic and biotic induced plant responses are not restricted to secondary metabolism, but also include changes in various primary metabolic pathways. For example, depending on the herbivore feeding style, a broad range of effects of herbivory on photosynthesis as the plant's main primary metabolic process has been reported. Pioneering studies of herbivore-induced changes in photosynthesis found the majority of defoliating herbivores causing an increase in photosynthetic activity, whereas mesophyll and phloem feeders, stem borers and gall formers mainly decreased photosynthesis in the remaining plant tissue. Recent gas exchange measurements and PSII electron efficiency studies from the use Fluorimaging systems have demonstrated reduced photosynthesis in herbivore- or mechanically damaged plant tissue demonstrating negative impacts of herbivory on plant fitness. Because these leaf-level photosynthetic measurements are time consuming, we developed a rapid screening method that allows one to measure variation in PSII electron efficiency in response to chemical treatments on many (up to 96) plants simultaneously using a CF Fluorescence Imaging system (Technologia, UK). We developed this method so that it can be used in both studies investigating how abiotic and biotic stress impacts leaf level fitness. Our main focus in this study was to address insect herbivory on leaf-level fitness by specifically monitoring changes in PSII electron efficiency as well as leaf level photosynthesis using a LICOR gas exchange system. We tested various photosynthetic inhibitors on leaves of Brassica rapa (Fast Plant) and Nicotiana attenuata (Tobacco), in conjunction with applying mechanical damage to leaves with the goal to determine how variations in herbivore saliva applied to leaf surfaces or injected into leaves alter leaf level fitness.I also presented a talk at the BSA 2012 meeting
My Symposium on Plant Water Relations (co-organized with Brandon Pratt from U.C. Bakersfield)
Water transport in plants at multiple scales: A physiological, ecological, and evolutionary appraisal
Peter J Melcher1 (presenter and organizer) and Brandon Pratt2 (co-organizer)
1Ithaca College; 2California State University, Bakersfield
This symposium topic and speakers will provide insight on plant water relations that spans across the whole plant, from the cellular to organismal levels, from basal lycophytes to derived angiosperms, and from physiological, ecological, and evolutionary approaches. This will provide an integrated view of whole plant water relations. In this area of research, there have been many recent advances in our understanding of long-distance sap transport at the cellular, tissue, organ and whole plant level. These include a finer understanding of the role of proteins that can trigger cascade responses within living cells at the root, stem and leaf-level resulting in altered properties of the dead xylem through unexpected mechanisms. For example, the ion-mediated regulation of xylem hydraulic resistance that may provide plants with a mechanism to control water distribution throughout their bodies. The potential role of xylem-phloem interactions, where sugar-loading may provide the necessary water potential gradient required to re-fill embolised conduits during times when negative tissue water potentials exist. Ecological strategies of plants to tolerate changes in seasonal water stress, assessed at the whole plant level, will also be discussed and this will provide insight to understanding how plants alter root, stem and leaf-level traits that result in enhanced fitness across changes in water availability. Also, water distribution regulation mechanisms measured at the leaf level, from stomatal response, to changes in leaf-level hydraulic resistance, and how altered leaf form across individuals, and varied plant forms will be discussed. Lastly, a macroevolutionary analysis of vascular transport will consider vascular function from lycophytes to conifers, which will provide a broad evolutionary context for the evolution of vascular structure and function.
INVITED SYMPOSIUM SPEAKERS:
Jarmila Pittermann (presenter) .
University of California, Santa Cruz
Xylem structure-function relationships in basal tracheophytes.
Taryn Bauerle (presenter).
Cornell University
Fine root spatial and temporal dynamics under limited soil moisture.
McCulloh, Kate (presenter), Daniel Johnson, David Woodruff, Frederick Meinzer.
Oregon State University.
Contrasting axial patterns in xylem hydraulic traits may reflect
Maciej Zwieniecki (presenter), Francesca Secchi.
Harvard University
Molecular understanding of xylem refilling.
Anna Jacobsen (presenter), Brandon Pratt, Michael Tobin, Uwe Hacke, Frank Ewers.
Xylem vessel length of woody plants: An ecological and evolutionary analysis.
Brandon Pratt (presenter)
University of California, Bakersfield
The use of centrifugation to assess xylem embolism in long-vesseled species.
- For full details and a list of speakers, follow the link.
Presented: "A new approach to measure hydraulic resistance in plants" - Peter Melcher
A new measurement protocol to measure hydraulic resistance in plants has been developed to remove errors associated with measuring hydraulic resistance on stem segments that result from the following: 1. working with samples that are shorter than the length of open conduits; 2. from creating artificial hydraulic paths on excised stems that have multiple years of growth that may result in perfusion solution freely flowing through pathways that do not exist in the intact plant (xylem sap in an intact stem would have to cross from older growth rings to younger growth rings at nodes); and 3. from samples that have alternative non-xylem flow paths, such as aerenchyma, thus reducing the true intact values of hydraulic resistance. This new method provides a more accurate assessment of hydraulic resistance in plants especially when measurements are made on species with long conduits (greater than the length of the sample) and with those that contain multiple (>3years) of vascular growth. A key issue that had to be resolved in order to employ this new method required that samples being measured were not wounding in response to being excised for measurement. A rapid (within seconds of excision) xylem-mediated wound response was found to be very common in most species surveyed. This wound response resulted in reduced flow by up to 80% in 5 mins in some species. Results from the use of the subtraction method in eight species will be presented. Briefly, we found that in all species studied the new subtraction method resulted in higher resistance values when compared to traditional methods, with large ranges in differences between the two methods that were species dependent. For example, Acer saccharum had resistance values that were twice as high compared to traditional methods and in other cases the differences between the two methods were only about 10%. Robinia pseudoacacia resistance values were the same for both methods. It is believed that the formation of tyloses in the older xylem of R. pseudoacacia reduces artificial flow paths from older xylem when excised for measurements. These data suggest that this new method provides a more accurate and more meaningful approach to measuring hydraulic resistance in plants. This is especially important when working with woody stems that have multiple years of growth and because it provides a measurement of hydraulic resistance that takes into account the way in which plants grow.
