ASGSB 1999 Annual Meeting Abstracts

[7]

INCREASED PEROXIDASE ACTIVITY IN WHEAT LEAVES FOLLOWING EXPOSURE TO LOW LEVELS OF ETHYLENE. J. Conlin¹, O. Monje², A. Anderson³, and G.E. Bingham¹. ¹Space Dynamics Lab and Utah State University, Logan, UT, ²Dynamac Corp., Kennedy Space Center, FL, 3Dept. of Biology, Utah State University, Logan, UT.

Super Dwarf wheat aboard the space station MIR and exposed to ethylene levels above 1.0 ppm developed abnormally and failed to set seed. In this ground study, the effects of low level ethylene treatments upon leaf peroxidases were studied. Two wheat cultivars (Super Dwarf and the semi-dwarf Apogee) were grown in stress-free conditions at 1200 µmol mol^-1 CO₂ and exposed to 0, 0.25, 0.50, 0.75 and 1.0 ppm of ethylene from Day 8 after emergence until maturity. We found increased peroxidase specific activities and altered isozyme composition in extracts from fully-expanded Super Dwarf and Apogee leaves, even at the lowest ethylene treatment (0.25 ppm).  By Day 42 after planting, Super Dwarf and Apogee extracts had similar peroxidase specific activities. The response of peroxidase specific activities was concentration dependent and described by a parabola that peaked near 0.50 ppm. However, at Day 22, Apogee extracts had much higher peroxidase specific activities than Super Dwarf extracts from the same day. Isoelectric focusing gels showed an increase in cationic peroxidases from ethylene treatments in both Super Dwarf and Apogee leaf extracts.  Peroxidase isozyme patterns were similar in both species with the exception of a cationic band that was observed only in Apogee extracts (pI 7.0).  These results suggest that leaf peroxidase specific activity may be a suitable marker for detecting and quantifying exposure to ethylene in space biology experiments. These results also suggest that endogenous ethylene may elicit cultivar-dependent effects (i.e., seed reproduction and pathogen sensitivity) in wheat via the differential accumulation of peroxidases.

(Supported by Space Dynamics Lab, Dept. of Biology and Dept. of Plants, Soils, and Biometeorology, Utah State University.)

Back to Meeting Program