Singlet oxygen quenching by phenylamides and their parent compounds.

This paper demonstrates for the first time that plant metabolites of the phenylamide type, conjugates of putrescine with hydroxycinnamic acids (p-coumaric, caffeic and ferulic), possess 1O2 quenching properties. Data were obtained confirming that their acidic parent compounds were also able to quench 1O2, as did polyamines (putrescine, spermidine and spermine), and that this ability depends on the number of amino groups. Potentiation of the 1O2 quenching ability of the conjugates relative to both parent components was established.

Contribution of photosynthetic electron transport, heat dissipation, and recovery of photoinactivated photosystem II to photoprotection at different temperatures in Chenopodium album leaves.

Temperature dependence of photoinhibition and photoprotective mechanisms (10-35 degrees C) was investigated for Chenopodium album leaves grown at 25 degrees C under 500 micro mol quanta m(-2) s(-1). The fraction of active photosystem II (PSII) was determined after photoinhibitory treatment at different temperatures in the presence and absence of lincomycin, an inhibitor of chloroplast-encoded protein synthesis. In the absence of lincomycin, leaves were more tolerant to photoinhibition at high (25-35 degrees C) than at low (11-15 degrees C) temperatures.