Effect of Alloxydim on Phospholipid Acyl Hydrolase, Wax Ester Synthetase and Ethanol Esters Synthetase Activity in Roots of Graminicide-sensitive Wheat Plants
 Walentyna Banaś1, Katarzyna Jasieniecka-Gazarkiewicz2, Kamil Demski2
 Antoni Banaś2
1Institute of Biology, University of Natural Sciences and Humanities, Siedlce, Poland
2Intercollegiate Faculty of Biotechnology of UG and MUG, Gdańsk, Poland

Alloxydim belongs to graminicides, herbicides selectively destroying plants from grass family with generally no effect on dicotyledonous plants. The inhibition of fatty acid biosynthesis was suggested as a cause of their phytotoxicity. However, there are some suggestions that inhibition of fatty acids is not the only (or maybe not even the main) reason of graminicides phytotoxicity. 
In our earlier studies we have shown that microsomal membranes from Arabidopsis leaves and roots can efficiently acylate free fatty acids (without prior activation to acyl-thioesters) to long chain alcohols. These membranes can also acylate free fatty acid to ethanol, producing ethanol esters. Production of ethanol esters correlated with phospoholipase activity we observed also in assays with wheat root extracts. 
	In the presented study we showed, using both microsomal preparation and crude extract of wheat roots, that phospholipid acyl hydrolase activity is several times higher in older part of roots compared with root tips, contained meristematic and elongated cells. When the wheat roots were grown in the presence of alloxydim (a grass herbicide) for a 48hrs, the phospholipid acyl hydrolase activity increased in root tips about 20 times and only about 2 times in older part of roots. The phospholipid acyl hydrolase activity was well correlated with ethanol ester synthase activity and wax ester synthase activity. They activity were several time higher in older part of wheat roots compared to root tips end were strongly activated by alloxydim treatment (especially in root tips). All three discussed enzymatic activities observed in wheat roots were very efficiently inhibited by lipase inhibitor - tetrahydrolipstatin - suggesting its lipase nature. The fact that the activities of aforementioned enzymes were especially increased in root tips of alloxydim treated plants – the place where the graminicide phytotoxic effects are the most strongly visible – suggests that studied enzymes could be involved in mechanism of action  grass herbicides.