High-temperature damage and acclimation of the photosynthetic apparatus

Abstract

The thermosensitivity of delayed fluorescence, the relative values of variable chlorophyll fluorescence and the degree of quenching of 9-aminoacridine fluorescene were studied in the chloroplasts from heat-acclimated and non-acclimated (treated 6 h at 52,5°C) young bean plants. The temperature sensitivity of each parameter studied was defined by that temperature at which chloroplast activity decreased by 50% (T50) of its maximum value. There was appreciable increase in the thermostability of membrane energization in chloroplasts isolated from acclimated and non-acclimated plants compared with the controls. The photosynthetic parameters differed according to the suspending medium and the preacclimation treatment. When chloroplast were suspended in phosphate buffer with the addition of stabilizing compounds (2 M sucrose or 0.5% human serum albumin) the thermostability of the thylakoid membranes increased, as was evident by the increases in T50 of about 8-10° C (sucrose) and 2-5° C (human serum albumin) for all the parameters investigated. Photoinduced quenching of 9-aminoacridine fluorescence decreased to some extent in the presence of protective compounds, but in chloroplasts from acclimated plants the T50 was practically equal to that for their long-lived luminescence under the same conditions. At the thylakoid membrane level, acclimation was clearly manifested as an increased thermostability of photoinduced proton-gradient formation.

TFA and EPA Productivities of Nannochloropsis salina Influenced by Temperature and Nitrate Stimuli in Turbidostatic Controlled Experiments

“…Furthermore, an enhanced EPA content in glycerol lipids of the thylakoid membranes protects the photosynthetic apparatus against low temperatures [42]. This is corroborated by the fact, that photosystem II is the most temperature sensitive component of the photosynthetic apparatus [43,44]. Therefore, the enhanced EPA concentration seemed to be a protection mechanism of Nannochloropsis salina against low temperature conditions.…”

Heat-induced impairments and recovery of photosynthetic machinery in wheat seedlings. Role of light and prooxidant-antioxidant balance

“…Photosynthesis is one of the most heat sensitive cellularfunctions (Berry and Björkman, 1980;Yordanov et al, 1986). The subsequent recovery of photosynthetic activity in the presence of light from heat injuries caused due to as sudden rise in environmental temperature has been well documented (Kadir S and Von Weihe, 2007).…”

Stimulation of chlororespiration by heat and high light intensity in oat plants

“…When leaves of plants are exposed to light intensities that exceed their photosynthetic capacity, excess photons promote the production of ROS and cause the photoinhibition of photosynthesis, and the photosynthetic apparatus is damaged (Powles 1984). Heat stress can alter the organization of the thylakoid membranes and inhibit photosynthetic electron transport (Yordanov et al . 1986; Schreiber & Berry 1977).…”