Effect of morpho-anatomy of Chenopodium album L. and Abutilon theophrasti medik. on response to mesotrione

Radi sagledavanja uticaja različitih faktora (faze razvija, morfo-anatomske građe listova i površinskih struktura lista) na osetljivost Chenopodium album i Abutilon theophrasti prema mezotrionu obavljena su istraživanja u kontrolisanim uslovima. Eksperimenti su realizovani u laboratorijama Poljoprivrednog fakulteta u Beogradu tokom 2016-2017. godine. Biljke ispitivanih vrsta su gajene u komori za gajenje biljaka, a kada su dostigle odgovarajuću fazu razvoja primenjen je herbicid mezotrion u odgovarajućoj količini/količinama. Za potrebe procene uticaja faze razvoja na osetljivost C. album i A. theophrasti prema mezotrionu biljke u različitim fazama razvoja (C. album: 2, 4, 6, 8 i 10 razvijenih listova, A. theophrasti: 1, 2, 3, 4 i 5 razvijenih listova) su tretirane preporučenom količinom (120 g a.s. ha-1) mezotriona. U cilju utvrđivanja osetljivosti biljaka prema mezotrionu u fazi koja se pokazala kao najosetljivija (C. album: 4 razvijena lista; A. theophrasti: faza 2 razvijena lista) primenjene su rastuće količine herbicida kako bi se procenile efektivne doze (3,75, 7,5, 15, 30, 60 i 120 g a.m. ha-1) na osnovu sledećih parametara: suva masa biljaka, odnos varijabilne i maksimalne fluorescencije, efektivni prinos fluorescencije PSII, intenzitet ozelenelosti listova, relativni sadržaj hlorofila i sadržaj karotenoida. Kako bi se utvrdio uzrok smanjenja osetljivosti biljaka C. album i A. theophrasti prema mezotrionu sa starenjem, analizirana je anatomska građa listova (debljina lista, debljina epidermalnih ćelija lica i naličja lista, debljina mezoila, palisadnog i sunđerastog tkiva), površinske strukture lista (broj voštanih žlezda i stoma prisutnih na licu i naličju lista C. album, odnosno broja dlaka i stoma prisutnih na licu i naličju lista A. theophrasti), kao i epikutikularni voskovi. Dobijeni rezultati su pokazali da faza razvoja u vreme primene mezotriona značajno utiče na osetljivost obe ispitivane vrste (C. album i A. theophrasti). Primena preporučene količine herbicida mezotrion u najranijim fazama razvoja dovela je do veoma visoke redukcije mase biljaka (>90%), ali se sa starenjem biljaka osetljivost smanjivala (redukcija mase 120 g a.s. ha-1), što ukazuje da ovi parametri nisu podesni za ocenu osetljivosti biljaka prema mezotrionu...In order to examine the influence of factors such as growth stage, morpho-anatomical structure of leaves and structures on leaf surface on the susceptibility of Chenopodium album and Abutilon theophrasti to herbicide mesotrione. The experiments were conducted in the glasshouse laboratories of the Faculty of Agriculture in Belgrade during 2016 and 2017. The plants were cultivated in a growth chamber, and after reaching the suitable growth stage, the relevant amount of mesotrione was applied. To assess the influence of the growth stage on the sensitivity of C. album and A. theophrasti to mesotrione in different growth stages (C. album: 2, 4, 6, 8 and 10 leaves, A. theophrasti: 1, 2, 3, 4 and 5 leaves) plants were treated with the recommended amount (120 g a.i. ha-1) of mesotrione. In order to determine the susceptibility of plants to mesotrione at the stage that proved to be the most sensitive (C. album: 4 leaves; A. theophrasti: phase 2 leaves), different amounts of mesotrione were applied to estimate the effective doses (3.75, 7.5, 15, 30, 60 and 120 g a.i. ha-1). Following parameters were measured: plant dry weight, variable and maximum fluorescence ratio, effective PSII fluorescence yield, leaf greening intensity, relative chlorophyll content and carotenoid content. In order to determine the cause of decreased sensitivity of C. album and A. theophrasti plants to mesotrione with each growth stage, the following analses were conducted: the anatomical structure of leaves (leaf thickness, thickness of epidermal cells on the adaxial and abaxial side, thickness of mesophyle, palisade and sponge tissue), leaf surface structure (the number of wax glands and stoma present on the adaxial and abaxial side of C. album leaves, the number of thrichomae and stoma present on the adaxial and abaxial side of A. theophrasti leaves), as well as content of epicuticular waxes on leaves. The results showed that the growth stage at the time of mesotrione application significantly affected the sensitivity of both species. The application of the recommended dose of mesotrione in the earliest growth stages led to a very high reduction in plant mass (>90%), but with plant maturation, the sensitivity decreased (mass reduction <60%). Furthermore, based on the same parameter (dry mass of plants) after applying different amounts of mesotrione, less than 50 g a.s. ha-1 were sufficient to reach ED95 when C. album is in stage 4 leaves and A. theophrasti is in stage 2 leaves. To reduce chlorophyll fluorescence by 95% (ED95) 85 g of mesotrione ha-1 needs to be applied. However, mesotrione did not cause rapid changes in leaf greenness and relative chlorophyll content in leaves of treated plants (ED95> 120 g a.s. ha-1), indicating that these parameters are not suitable for assessing plant susceptibility to mesotrione..