Leland S. Jahnke

Leland S. JahnkePh.D. University of Minnesota

Plant Physiology

Ultraviolet Radiation and Oxidative Stress

Physiology and Biochemistry of Dunaliella

lsj@unh.edu

 

 

 

 

Current Teaching Areas

  • Introductory Botany
  • Economic Botany
  • Photosynthesis
  • Stress Physiology
  • Algal Physiology
  • Algal Physiology Laboratory

Current Research

OXIDATIVE STRESS IN PLANTS AND ALGAE

Photosynthetic cells in leaves and in algae function in an environment that often contains hyperbaric oxygen (created directly by the water-splitting reactions) and high light intensities which are efficiently absorbed by the photosynthetic pigments. The combination of efficient light absorption in a high oxygen environment creates potentially toxic forms of oxygen. The interaction of additional physical stress factors (low temperatures or ultraviolet radiation) with this internal chloroplast environment is the main interest of my research program.

Plants and algae evolved in an environment that was exposed to much higher levels of ultraviolet radiation than that of the present day. Various defenses evolved to ameliorate the adverse effects of this radiation. The nature and function of some defenses is becoming well understood (DNA reactivation), but the roles of others (antioxidant substrates and enzymes) are poorly characterized. Low non-freezing temperatures likewise are often major stress factors that interact with light and oxygen to cause an impairment of photosynthesis. Our research effort is investigating the antioxidant acclimation of tolerant and susceptible species of higher plants and algae to near-ultraviolet radiation or chilling stress. Both membrane antioxidant systems (carotenoid, xanthophyll cycle, and tocopherols), as well as aqueous systems (i.e. superoxide dismutases, peroxidases and glutathione, and ascorbate) are being examined.


oxidative stress diagram


Recent Publications

  • White, A.L. and L.S. Jahnke. 2002. Contrasting effects of UVA and UVB on photosynthesis and photoprotection of B-carotene in two Dunaliella spp. Plant Cell Physiol. 43:877-884.
  • Jahnke, L.S. 1999. Measurement of hydroxyl radical-generated methane sulfinic acid by high-performance liquid chromatography and electrochemical detection. Anal. Biochem. 269:273-277.
  • Jahnke, L.S. 1999. Massive carotenoid accumulation in Dunaliella bardawil induced by ultraviolet-A radiation. J. Photochem. Photobiol. 48:68-74.
  • Hull, M.R., S.P. Long, and L.S. Jahnke. 1997. Instantaneous and developmental effects of low temperature on the catalytic properties of antioxidant enzymes in Zea species. Austral. J. Plant Physiol. 24:337-343.
  • Jahnke, L.S. and A.L. White. 2003. Long-term hyposaline and hypersaline stresses produce distinct antioxidant responses in the marine alga Dunaliella tertiolecta. J. Plant Physiol. 160:1193-1202.