Research

Research:

Our broad research interest is in plant ecophysiology with primary aim of understanding the significance of various plant secondary-metabolites in shaping plant communities. Specifically we focus on the chemical and biological interactions that take place in plant-soil interface

The lab has two research foci- one basic and one applied. The focus of our basic research is in understanding the role of plant secondary-metabolites in shaping plant communities through:

  1. litter decomposition and soil nutrient cycling
  2. negative plant-to-plant interactions [allelopathy]
  3. root exudates mediated nutrient acquisition [resource foraging]
  4. plant-to-plant communications [root signaling].

Our applied research, driven by our basic research, focuses on:

  1. optimizing allelochemical production in cover-crops for organic weed management,
  2. prediction and management of habitat specific plant invasions based on physiochemical traits of exotic plant species.
  3. employing exudate mediated nutrient-aquisition techniques in crop production

 

Ongoing Projects:

Mechanism of invasion of clonal plants {Funding: USDA-NRI (2009-2012)}

The two long term goals of this project are:

  1. To better understand the mechanisms through which clonal invasive plants alter ecosystem functioning in poorly managed agricultural systems, so as to facilitate their further spread (niche construction)
  2. To test the recolonization success in these invaded agricultural landscapes by native species subsequent to the reversion of the above niche construction.

Disturbances caused by cultivation practices expose agricultural fields and pastures to invasion by exotic plants after they are fallowed or abandoned. Non native plants with clonal characteristics [the production of asexual offspring (ramets) that remain attached to the parent plant] form persistent monoculture stands in the above settings, resulting in decreased productivity of pasturage, hampering the conversion of agro-ecosystems to native grasslands and forests, jeopardizing the ecosystem-services provided by field margins to agriculture -like pollination, and increasing the cost of bringing the fallowed land back to cultivation. The mechanisms that facilitate the spread of clonal species, and the restoration practices needed to control them are important and under-studied aspects of the biology of weedy species in agroecosystems. We use a noxious clonal weed, Japanese knotweed (Polygonum cuspidatum), as a model plant in this study. Firstly we will identify the importance of i) physiological integration, nutrient translocation between connected ramets and the litter quality in changing the nutrient cycling ii) microclimate modification through microbial associations, and production of toxic compounds by P. cuspidatum in the invaded sites of eastern United States. Secondly, based on the identified mechanism of invasion, we would formulate different management practices to i) restore nutrient cycling to pre-invade levels and ii) to nullify the toxic effects, followed by the reseeding of the native species and quantify the success of restoration of invaded habitats.

Along with the macroscopic measurements of soil nutrient dynamics, we will be utilizing Fourier Transform Infrared Spectroscopy (FTIR) and cross polarization/magic angle spinning carbon-13 nuclear magnetic resonance (CP/MAS 13C NMR) spectroscopy to identify the change in litter chemistry, phospholipid fatty acid (PLFA) analysis to assess the shift in microbial community composition.

Mechanisms of a root-exudate mediated nutrient uptake in plants {Funding- USDA-AFRI (2009-2011); Support- Argonne National Lab, Chicago IL}

Sixty to eighty percent of the world’s population is estimated to be iron-deficient making it the leading human nutritional disorder in the world today. Hence, iron content in plants, the primary source of Fe nutrition to humans, is important. Fe, though the fourth most abundant element in the Earth’s crust, is the third most limiting nutrient for plant growth due to its limited solubility. While investigating the competitive characters of a non-native plant species-Centaurea diffusa, we found that its secondary metabolite, 8-hydroxyquinoline (8HQ), could directly facilitate the uptake of Fe from the alkaline soils it invades. Exogenously supplied 8HQ-Fe complex (FeQ) was equally effective in supplying Fe to both graminaceous and nongraminaceous species, as well as to Zea mays mutant (ys1) that lacks the ability to take up iron-complexes. Our studies indicate that the lipophilic FeQ could be passively diffusing into the cells, a phenomenon novel to the plant world. This less energy intensive mechanism could be used to increase the Fe status of crops by use of FeQ as a synthetic chelant for Fe nutrition in plants. Our current understanding about the mechanism of uptake and further transport of Fe facilitated by 8HQ rely on indirect measurements. More direct measurements showing the presence of undissociated FeQ inside the plant system, and the role played by 8HQ in internal Fe-transport and homeostasis are needed to further understand FeQ-mediated Fe nutrition in plants. Using synchrotron micro-X-ray Fluorescence and micro-X-ray Absorption Spectroscopy we are investigating the Fe-speciation in various crop plants at different stages of uptake and utilization of FeQ. The main questions that we are addressing in the this study are whether i) FeQ enters the plant cell without undergoing chelate splitting, ii) uptake of FeQ is passive, and iii) 8HQ facilitates the transport of Fe inside the plant.

Soil processes in a changing climate

Decomposition of plant litter and soil organic matter sustain ecosystem productivity by controlling nutrient recycling rates. Environmental factors such as soil moisture, temperature and soil nutrients influence the chemical composition of plant communities. Resource limitation and stress caused by climate change could instigate plants to invest more on secondary metabolites including low molecular weight monomeric compounds (phenolics, phenyl propanoids and flavanoids) and large polymeric compounds (lignin and tannins). This abundance of secondary compounds can affect the soil nutrient cycling i) biologically and ii) chemically. Our ongoing study aims to address the current knowledge gap in how the environmental stress caused by climate change affect diversity of plant secondary metabolites, and how these metabolites further influence litter decomposition and nutrient cycling.

Root-rhizosphere interactions in facilitating plant invasions.

Rhizodeposition accounts for >50% of the photosynthates lost from plants under stressed condition. Though seemingly suicidal, this ‘wastage’ of assimilated carbon is found to give competitive advantage to some of the non-native plant species. Using various exotic species in the genus Centaurea, we are investigating the significance of root exudates in facilitating invasion in resource poor habitats - directly through resource foraging; and indirectly through allelopathy, microbial community shifts and associated changes in rhizosphere nutrient dynamics.

Collaborators:

Peter Alpert- University of Massachusetts Amherst
Ragan Callaway- University of Montana
Jeffrey Dukes- Purdue University
Matt Newville – Argonne National Lab, Chicago
Kirk Scheckel-US EPA
Elsbeth Walker- University of Massachusetts Amherst
Dong Wang- USDA
Baoshan Xing – University of Massachusetts Amherst