Photosynthetic efficiency of Japanese knotweed (Reynoutria japonica Houtt.) in stressful conditions

Niske temperature mogu predstavljati stresne uvjete za biljke i negativno utjecati na njihove fiziološke i biokemijske procese kao što je fotosinteza. Cilj ovog rada bio je proučiti utjecaj niske temperature (5°C) na fotosintetsku učinkovitost Japanskog dvornika (Reynoutria japonica Houtt.) nakon različite duljine izlaganja (1, 2, 4, 6, 8, 16, 24 i 48 sati). U tu svrhu mjerena je fluorescencija klorofila a. Analizom parametra JIP-testa opisan je prijenos energije reakcijskim središtima fotosustava II te indeks fotosintetske učinkovitosti (PIABS). Kratkotrajna izlaganja biljaka niskoj temperaturi (1-16 sati) nisu pokazala negativan utjecaj na prijenos energije po aktivnom reakcijskom središtu, dok je kod dugotrajnijih izlaganja (24 i 48 sati) niska temperatura dovela do stvaranja neaktivnih, odnosno „utišanih“ reakcijskih središta. Smanjenje indeksa fotosintetske učinkovitosti (PIABS) već pri kratkom izlaganju niskoj temperaturi ukazuje na ograničenje prijenosa elektrona dalje od primarnog akceptora u transportnom lancu elektrona.Low temperatures can present stressful conditions for some plants and it can have a negative effect on their physiological and biochemical processes such as photosynthesis. The aim of this study was to determine the effect of low temperature (5°C) on photosynthetic efficiency of Japanese knotweed (Reynoutria japonica Houtt.) after different length of exposure (1, 2, 4, 8, 16, 24 and 48 hours) on its.). To determine the parameters of photosynthetic efficiency, the chlorophyll a fluorescence was measured. The analysis of JIP test parameters described the energy transfer through reaction centres of photosystem II and the performance index (PIABS). Short-term exposures of plants to low temperature (1-16 hours) did not show a negative impact on energy fluxes per active reaction centre, while longer exposures (24 and 48 hours) to low temperature caused the formation of inactive or "silent" ones. The decrease of performance index (PIABS) even at short exposure to low temperature indicated a limitation of electron transport after the primary acceptor in the electron transport chain