Different aspects of inhibition of growth and photosynthesis by the phosphonate herbicide sulphosate in maize (Zea mays L.), 4: Influence on plants grown in controlled environment

Abstract

Effect of the herbicide sulphosate on the growth, accumulation and distribution of dry weight, photosynthesis and water regime in maize plants grown in controlled environment was investigated. The herbicide sulphosate was found to significantly lowered dry matter acumulation and slow down growth of maize plants. Dry weight accumulation, which ultimately determines growth, was found to correlate highly significantly with dry matter allocation to root and leaves, but this dependence was not unique. Under influence of sulphosate dry matter allocated from leaves to stem. That the phenomena result from a specific carbohydrate metabolism in stem of maize plants (not contain starch). The herbicide sulphosate significantly affect the status and functioning of the root and water regime of maize plants (lowered values of parameters Vr and RWC). Changes in photosynthesis and photosynthetic structures (degradation of photosynthetic pigments) under the effect of sulphosate precede changes in the water regime of leaves of maize plants. This effects must be seen as photoinhibition of photosynthesis with photooxydation of photosynthetic pigments (particularly Chla) under sulphosate-provoked stress. 'Light curves' of different parameters of Chla fluorescence (qP, Fv,/Fm,, Φ PS2) lowered under increased actinic light. ETR para-meter of photosynthesis had sigmoid dependence of PAR, like to kinetic of photosyntetic fixation of CO2. Parameters of Chla fluorescence and photosynthesis can be used to monitor and assess the volume of functional senescence of photosynthesis in maize leaves both in the control plants and those exposed to sulphosate-caused stress.

U radu se razmatra dejstvo herbicida sulfosata na rastenje, akumulaciju i preraspodelu suve mase, fotosintezu i vodni režim biljaka kukuruza, raslih u kontrolisanim uslovima. Herbicid sulfosat značajno umanjuje akumulaciju suve mase, usporava rastenje biljaka kukuruza i utiče na preraspodelu suve mase u biljci. Poslednji efekat verovatno je u vezi sa specifičnošću metabolizma ugljenih hidrata u stablu kukuruza. Akumulacija suve mase i rastenje kukuruza zavise od preraspodele suve mase u koren i listove, što bi bio jedan od uzroka fitotoksičnog dejstva sulfosata. Pored toga, sulfosat inhibira funkcije korena i vodni režim listova kukuruza. Ipak, najraniji efekat sulfosata jeste fotoinhibicija fotosinteze, za kojom sledi degradacija fotosintetskih pigmenata i struktura. Metoda fluorescencije Chla može se koristiti za in situ praćenje funkcionalnog starenja listova u stanju stresa, kao npr. pri dejstvu herbicida sulfosata.