Heat inactivation of various photosynthetic electron transport reactions were investigated in the presence/absence of glycinebetaine (betaine) in unstacked thylakoid membranes from spinach. The activity of Photosystem II (PS II) is more sensitive to heat than that of Cytochrome bf (cyt.bf) and Photosytem I (PS I) complexes. The data obtained clearly demonstrated the protection of PS II and PS I electron transfer by betaine under high temperatures. The phenomena observed are probably related to the stabilization of the higher-order structures of PS II and PS I by betaine.

Heat inactivation of various photosynthetic electron transport reactions were investigated in the presence/absence of glycinebetaine (betaine) in unstacked thylakoid membranes from spinach. The activity of Photosystem II (PS II) is more sensitive to heat than that of Cytochrome bf (cyt.bf) and Photosytem I (PS I) complexes. The data obtained clearly demonstrated the protection of PS II and PS I electron transfer by betaine under high temperatures. The phenomena observed are probably related to the stabilization of the higher-order structures of PS II and PS I by betaine.