The influence of annual changes in temperature and light (PAR) on the induction of Chla fluorescence in situ in Stellaria media (L.) and Plantago maior (L.)

Abstract

Chla fluorescence, as a mode of estimation of photosynthesis, is especially sensitive to changes in temperature and light intensity (PAR). This enables us to study the influence of those ecophysiological parameters on photosynthesis in native plants. In this article, we examined the effect of annual changes in temperature and PAR on the parameters of Chla fluorescence in Stellaria media (L.), a plant species more frequent in colder periods of the year, and Plantago maior (L.), which is more frequent in warmer periods. Lower PAR and temperature slowed down the electron transport in PS2, but lower temperatures reduced the quantum efficacy of PS2 and improved processes in the antennae system and the size of plastoquinone pool of PS2 in Stellaria media (L.). Lower temperatures reduced quantum efficacy and slowed down the electron transport in PS2 in Plantago maior (L.). The facts that PAR (as well as temperature) affects photosynthesis, and that lower temperatures activate processes in the antennae system and those on the acceptor side of PS2 as a 'counterbalance' to the inhibition of quantum efficacy and electron transport in PS2, caused by low temperatures, point at possible explanations of low-temperature resistance of photosynthesis in Stellaria media (L.). On the other hand, low temperatures caused inhibition of quantum efficacy and electron transport in the PS2 of Plantago maior (L.), which caused low-temperature photoinhibition and stepped quenching of all physiological processes in the species. This might be the reason for the different levels of acclimation to low temperatures and different life strategies of the two species living in close vicinity.

Fluorescencija Chla, kao pokazatelj fotosinteze, posebno je osetljiva na promene temperature i intenziteta svetlosti (PAR). To omogućava praćenje uticaja ovih ekofizioloških parametara na fotosintezu nativnih biljaka. U ovom radu dat je pregled uticaja godišnjih promena temperature i PAR na parametre fluorescencije Chla kod Stellaria media (L.), biljne vrste zastupljenije u hladnijem delu godine i Plantago maior (L.), biljne vrste zastupljenije u toplijem delu godine. Manje vrednosti PAR i temperature usporavaju transport elektrona u PS2, sniženje temperature umanjuje kvantnu efikasnost u PS2 i pozitivno deluje na antenske procese i veličinu pula plastohinona u PS2 kod Stellaria media (L.). Sniženje temperature umanjuje kvantni prinos i usporava transport elektrona u PS2 kod Plantago maior (L.). Činjenica da i PAR (pored temperature) deluje na fotosintezu, kao i da sniženje temperature aktivira antenske i procese na akceptorskoj strani PS2, kao "protivtežu" inhibiciji kvantne efikasnosti i transporta elektrona u PS2, uzrokovanoj niskim temperaturama, ukazuje na moguće uzroke niskotemperaturne otpornosti fotosinteze kod Stellaria media (L.). Nasuprot tome, kod Plantago maior (L.) niska temperatura uzrokuje inhibiciju kvantne efikasnosti i transporta elektrona u PS2, što dovodi do niskotemperaturne fotoinhibicije i postepenog gašenja svih fizioloških procesa kod te vrste. To bi moglo biti objašnjenje različite prilagođenosti na niske temperature i različitih životnih strategija ovih vrsta, koje žive u bliskom susedstvu.