Peter J. Melcher

Peter J. Melcher

Associate Professor, Department of Biology
Faculty, School of Humanities and Sciences
Faculty, Honors Program
Faculty, Premed Option

Recent Presentations (2010 - Present)

Invited Talks:

  • Do Plants Defy Physical Laws?  How plants move water against the forces of gravity and hydraulic resistance without using a heart-like pump. Peter Melcher. Ithaca College.Physics Department Seminar Series. Fall 2013.
  • The risky business of moving water long-distances under negative pressure in plant. Peter Melcher. Hamilton College, Utica NY. Biology Department Seminar Series. Fall 2012
  • Mission Impossible: Moving Water against the Forces of Evil (Gravity and Resistance) in Plants. Peter Melcher. Colgate University, Biology Department Seminar Series. Fall 2012.
  • Dying for a good cause - xylem pays the ultimate price for transpiration. Peter Melcher  UCLA - Department of Ecology and Evolutionary Biology: Discovering Nature Series. Spring 2010.

Presentations at Professional Meetings:

  • A new approach to measure hydraulic resistance in plants.  American Society of Plant Biology Northeastern sectional meeting in Rhode Island. Spring 2014. (oral)
  • A new approach to measure hydraulic resistance in plants.  Peter Melcher. Paper Presentation. Botanical Society of America Annual Meeting. Columbus, OH. 2012 (oral)

  • Importance of bridging phloem and xylem biologists to work together to understand mechanisms of embolism refilling.  Peter Melcher. Symposium Presentation. Botany Society of America Annual Meeting. Columbus, OH. 2012 (oral)

  • Water transport in plants at multiple scales: A physiological, ecological, and evolutionary appraisal. Organizer of Symposium: Peter Melcher and Brendan Pratt. Botanical Society of America Meeting. Columbus, OH. 2012 (oral)

  • A new approach to measure hydraulic resistance in plants. Peter Melcher. Botanical Society Meeting, Columbus, OH. 2012 (oral)

  • Functional embolism refilling in red maple (Acer rubrum L.). Peter Melcher, N. Michele Holbrook and Maciej Zwieniecki. Botanical Society of America Meeting. St. Louis, MO. 2011 (oral)

  • The impact of xylem wounding on the measure of stem hydraulic resistance. Peter Melcher and Steven Warchocki. Botanical Society of America Meeting. Providence, RI. 2010 (oral)

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Student Presentations 

2013 Botanical Society of America Meeting, New Orleans, LA. 

The physiological responses of moss to green light.              **Winner of the Physiological Section "BEST POSTER AWARD"***

Robert Griffin-Nolan* and Peter Melcher

The goal of this study was to determine if moss could use green light to power photosynthesis. Measurements were made on three species of moss (Dichodontium pellucidum (Schimp.),Amblystegium serpens (Schimp.), and Leucobryum albidum (Bird. ex P. Beauv)) collected from field sites that varied in their light conditions. We found that moss collected from the field could use green light to drive photosynthesis at rates similar to when exposed to red, blue, or full spectrum light (all measured at 100 umol m-1s-2). Mosses were also collected from the field and grown for three weeks under three light conditions: low and slightly higher full-spectrum light at 30 and 100 umol m-1s-2, respectively; and green light at 30 umol m-1s-2. We measured photosynthetic electron transport efficiency (ETR) using a LICOR 6400 leaf chamber Fluorometer. We found that mosses grown under only green light had similar ETR compared to plants grown under full spectrum light. From carbon and nitrogen isotope analysis, we found that moss exhibit resource allocation plasticity when exposed to different light environments. These data support our hypothesis that moss can use green light to power photosynthesis but the degree to which they use green light to overcome respiratory demands depends on their light environment (e.g. sun vs. shade). The mechanism by which plants use green light to photosynthesize is unclear. However, the fact that mosses are able use green light for photosynthesis suggests that the mechanism evolved early on in land plant history.

 

The effects of herbivory on leaf-level photosynthesis measured on wild tobacco plants.

Yongqian, Zhang*, Robert Griffin-Nolan, Leanne Donahue, Michael Guidi, Jason Hamilton, and Peter Melcher (Poster)

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 that the majority of defoliating herbivores cause an increase in photosynthetic activity, whereas mesophyll and phloem feeders, stem borers and gall formers mainly decreased photosynthesis in the remaining plant tissue. 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 include changes in various primary metabolic pathways. To investigate these plant-animal interactions, we are measuring leaf-level photosynthetic responses of wild tobacco plants collected from field sites in Arizona and Utah in response to various phytochemicals. Previously, our group showed that these wild tobacco plants respond to herbivory attack with increased photosynthesis from myriad bug herbivory and decreased photosynthesis from Manduca hornworm herbivory. Since these leaf-level photosynthetic measurements take an enormous amount of time, 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) samples simultaneously using a CF Fluorescence Imaging system (Technologia, UK). We were successful to measure changes in electron efficiency in the leaves of tobacco using two phytochemicals Jasmonic acid (JA) and Salicylic Acid (SA) compared to deionized water and an electron blocker (3-(3,4-dichlorophenyl)-1,1-dimethylurea (DCMU). Future work will involve measurements of chemicals extracted and isolated from wild myrid bug and manduca hornworm salivary glands on leaf-level electron transport efficiency and results from these studies will be presented.

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2012 Botany Society of America Annual Meeting. Columbus, OH.

The role of green light in photosynthesis in Bryophytes and higher plants

Robert Griffin-Nolan*, Rosen, Benjamin** and Peter Melcher.    

***WINNER OF THE PHYSIOLOGICAL LI-Cor Prize BEST POSTER***

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.

 

A rapid fluorescence imaging screening protocol to assess PSII electron efficiency of plants.

Leanne Donahue*, Robert Griffin-Nolan*, Jason Hamilton,  and Peter Melcher (Poster). 

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.

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 2011 Botanical Society of America Meeting, St Louis, MO.

  • Pamela Millan*, Peter Melcher and Lawren Sack. Intracanopy leaf plasticity and te impact of light versus height on carbon and nitrogen isotope discrimination for five temperate deciduous tree species. 

 

  • Marieke Brower, Robert Griffin-Nolan and Peter Melcher.  Investigating the role of green light in photosynthesis in Coleus spp.  

 

 

 

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