The modification of phytosterol profiles and in vitro photosynthetic electron transport of Galium aparine L. (cleavers) treated with the fungicide, epoxiconazole.

摘要

Foliar application of the triazole fungicide, epoxiconazole, retarded the growth of Galium aparine (cleavers). GC-MS and GC analysis clearly indicated that phytosterol biosynthesis in stem and leaflet tissue was significantly affected by this treatment. For example, in leaflet tissues, 125 g ai ha-1 (field rate) caused reductions in campesterol and sitosterol of 81 and 75%, respectively. C14-methyl phytosterol such as 14alpha-methylergost-8-enol, obtusifoliol and dihydroobtusifoliol were detected in treated tissues, indicating that epoxiconazole inhibits the cytochrome P-450 dependent obtusifoliol 14alpha-demethylase. In addition, ratios of campesterol to sitosterol were reduced. Stigmasterol was not detected in control or treated tissues. Preliminary determination of photosynthetic characteristics of isolated thylakoids from treated plants indicated that electron transport and oxygen evolution were impaired by epoxiconazole, and that these effects were dose-related. Ten days after treatment, oxygen evolution from thylakoids (determined as electron flow from water to ferricyanide) isolated from control plants was 24.2 鎚ol mg-1 chl h-1, whilst treatment with 125 g and 250 g ai ha-1 reduced this rate to 15.2 鎚ol and 8.2 鎚ol mg-1 chl h-1, an inhibition of 37 and 67% respectively. These results suggest that epoxiconazole influences thylakoid integrity and function in addition to phytosterol biosynthesis in G. aparine.