Forskning ved Københavns Universitet - Københavns Universitet

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Chlorophyll a fluorescence and herbicide efficacy, metabolism and selectivity

Publikation: Bog/antologi/afhandling/rapportPh.d.-afhandlingForskning

  • Majid Abbas Poor
Analysis of chlorophyll fluorescence induction curve (Kautsky curve) parameters was used for the study of the efficacy, metabolism and selectivity of ACCase, PSII and EPSPS inhibitors. Fv/Fm, Fvj and area above Kautsky curve and maximum fluorescence were selected among numerous fluorescence parameters for further analysis. All experiments were designed as dose-response relationship ranging from untreated controls to doses that kill plants. In greenhouse experiments, clodinafop, an ACCase inhibitor, changed the shape of the Kautsky curves in oats more severely than barley few days after spraying. Clodinafop is metabolized in barley sooner than in oats (Paper I). In hydroponics with root-applied PSII inhibitors; metamitron and terbuthylazine, recovery process was studied with Kautsky curves. Sugar beets recovered from metamitron injury at much higher doses than terbuthylazine. Metamitron is a herbicide designed to be selectively used in sugar beets and therefore being metabolized in sugar beets. Sugar beets in most cases died from terbuthylazine injury (Paper II).The shape of the Kautsky curves were changed few hours after spraying in sugar beets and black nightshade (Solanum nigrum L.), when sprayed with PSII inhibitors; phenmedipham, desmedipham and 50% mixture of phenmedipham plus desmedipham. Black nightshade’s kautsky curves were affected at much lower doses than sugar beets. Phenmedipham, desmedipham and their 50% mixture are selectively used in sugar beets to control broadleaf weeds like black nightshade (Paper III). In field studies with logarithmic sprayer the effects of glyphosate (EPSPS inhibitor) and terbuthylazine (PSII inhibitor)mixed with three EC non-ionic adjuvants (Torpedo-II, Li-700 and Validate) on the fluorescence parameters were investigated in spring barley by analyzing the changes in Kautsky curve. Torpedo-II significantly increased the herbicide effect on fluorescence parameters while Li-700 decreased the effect. Spring barley sprayed with glyphosate died few weeks after spraying whether mixed with adjuvants or not while completely recovering from terbuthylazine injury happened within few weeks (Paper IV). In growth chamber the 50% mixture of phenmedipham plus desmedipham changed fluorescence parameters more two hours after spraying than did phenmedipham alone. The plants in growth chamber were less sensitive than greenhouse experiments showing the importance of sunlight to induce herbicide damage as well as temperature and phenological stage of plants (Proceeding (paper V)). We found selected fluorescence parameters were closely linked to the dry matter dose-response relationships. The linkage between dry matter taken few weeks after spraying and fluorescence parameters taken few hours or days after spraying may be used to shortening the herbicide screening period. Analysis of the fluorescence parameters is an excellent tool to detect the effect of herbicides affecting photosynthesis directly (PSII inhibitors) or indirectly (ACCase and EPSPS inhibitors) in the broad sense. This method can be used to test the effect of different adjuvants on efficacy of herbicides soon after spraying and be helpful in the quest for new and improved formulations and adjuvants.
OriginalsprogEngelsk
Udgivelses stedCopenhagen
ForlagCenter for Skov, Landskab og Planlægning/Københavns Universitet
Antal sider102
StatusUdgivet - 2006

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