[36]

MECHANICAL STRESS AND WOUNDING ELICT NITRIC OXIDE PRODUCTION IN A. THALIANA WILD-TYPE AND NITRATE REDUCTASE MUTANTS. H. Garcкs^{1, 2}, D.J. Durzan² and M.C. Pedroso^1,2.  ¹Dept. Biologia Vegetal, Faculdade de Ciкncias, Universidade de Lisboa, Portugal, and ²Dept. Environmental Horticulture, University of California, Davis, U.S.A.

Nitric oxide (NO) is a signaling molecule that plays several important roles in plants. We investigated if mechanical stress (centrifugation) and wounding altered NO production in Arabidopsis thaliana leaves. We postulated that NO originated either from a putative nitric oxide-synthase (NOS), or by nitrate reductase (NR) activity. Leaves from wild-type and G’4-3 double NR mutant (nia1, nia2 mutant defective in the assimilation of nitrate from N. Crawford, UC San Diego) were centrifuged, and/ or wounded and then labeled with DAF-2 DA (4,5-diaminofluorescein diacetate) to visualize in vivo NO production. Results with the wild-type (control) and mutant indicated that the increase of NO production in leaves caused by centrifugation and wounding was not a product of NR activity. Moreover, endogenous NO production in both clones was suppressed by the NOS inhibitor N^G-monomethyl-L-arginine (L-NMMA). This was consistent with previous results in Taxus and Kalanchoл (Pedroso et al., 2000, J. Exp. Bot. 51: 1027-1036), reaffirming that a putative NOS activity is present in plants. 

(Supported by Fundaзгo para a Ciкncia e a Tecnologia, contract PRAXIS XXI 3/3.1/CTAE/1930/95 and GGPXXI/BD/3377/96.)