The effect of temperature and light (PAR) on the induction of Chla fluorescence in situ: 2. Diurnal changes in stinging nettle (Urtica dioica) and red currant (Ribes spp.)

Abstract

The phenomenon of a midday decrease in quantum and all other efficiencies of photosynthesis has been acknowledged. Quantum efficiency of PSII in nettle is known to be lower at midday than in the morning or evening. On other hand, the parameters of induction of Chla fluorescence in stinging nettle (Urtica dioica L.) during the daytime were shown to depend on temperature alone. An increase in temperature also slowed down processes in reaction centres (RCs) and on the acceptor side of PSII, which showed its effect on electron transport in PSII and overall photosynthesis. A similar situation was found for red currant (Ribes spp.). The temperature effect was considered to be transient thermal inhibition of photosynthesis caused by diurnal changes in temperature.

Razmatran je fenomen podnevne inhibicije kvantne efikasnosti i drugih aspekata fotosinteze. Parametri kvantne efikasnosti PSII kod koprive su niži u podne nego ujutro ili uveče. Nađeno je, u oglednim uslovima, da parametri indukcije fluorescencije Chla kod koprive (Urtica dioica L.) tokom dana zavise samo od promena temperature. Porast temperature usporava procese u reakcionom centru (RC) i na akceptorskoj strani PIII, što utiče na transport elektrona u PSII, kao i na ukupnu fotosintezu. Slična situacija je zapažena i kod ribizle (Ribes spp.). Zapaženi efekat temperature može se razmatrati kao privremena termalna inhibicija fotosinteze usled diurnalnih promena temperature. Mišljenja smo da je taj fenomen karakteristika ispitivanih biljaka iz jedne planinske ekološke niše, kao i specifičnih uslova merenja.