P. Jahns, THE XANTHOPHYLL CYCLE IN INTERMITTENT LIGHT-GROWN PEA-PLANTS - POSSIBLE FUNCTIONS OF CHLOROPHYLL A B BINDING-PROTEINS/, Plant physiology, 108(1), 1995, pp. 149-156
The xanthophyll cycle in pea (Pisom sativum L. cv Kleine Rheinlanderin
) plants has been investigated in vivo. Control plants were compared w
ith those grown under intermittent light (IML plants). IML plants are
particularly characterized by the absence of nearly all chlorophyll a/
b-binding proteins. The rates of de-epoxidation during 30 min of illum
ination and their dependence on the incident photon flux density (PFD)
have been determined. They were very similar in both types of plants,
with the exception that IML plants contained, at any PFD, much higher
zeaxanthin concentrations in the steady state (reached after about 15
min of illumination) than control plants. This indicates that the amo
unt of convertible violaxanthin under illumination is dependent on the
presence of chlorophyll a/b-binding proteins. The epoxidation rate (e
xamined at a PFD of 15 mu E m(-2) s(-1), after 15 min of preilluminati
on with different PFDs) showed significant differences between the two
types of plants. It was about 5-fold slower in IML plants. On the oth
er hand, in both types of plants, the epoxidation rate decreased with
increasing PFD during preillumination. Prolonged preillumination at hi
gh PFDs resulted in a decrease of the epoxidation rate without a furth
er increase of the zeaxanthin concentration in both continuous light a
nd IML plants. This result argues against a permanent turnover of the
xanthophylls under illumination, at least at high PFDs.