V. Spunda et al., APPEARANCE OF LONG-WAVELENGTH EXCITATION FORM OF CHLOROPHYLL-A IN PS-I FLUORESCENCE DURING GREENING OF BARLEY LEAVES UNDER CONTINUOUS LIGHT, Journal of photochemistry and photobiology.B, Biology, 40(2), 1997, pp. 149-153
The development of light harvesting complexes (LHCs) of both photosyst
ems in the course of greening of barley leaves was investigated using
the following three typical changes in 77 K chlorophyll a (Chl a) fluo
rescence spectra: (i) shift of PS I emission maximum to 741-743 nm tog
ether with its substantial increase; (ii) relative increase of Chl b e
xcitation maximum in the Soret region; (iii) shift of the red Chl a ex
citation maximum from 677 to 680 nm. Moreover, a pronounced long-wavel
ength excitation maximum of Chl a, E698, appeared in the red region of
77 K excitation spectrum for photosystem (PS) I emission after 32 h o
f greening. The rise of E698, which was observed for the first time as
a main excitation maximum in the red region of the excitation spectru
m for fully green barley leaves, is related to an increasing efficienc
y of energy transfer from LHCs to Chl a forms fluorescing both at 685
nm and 743 nm. For broken chloroplasts isolated from mature barley lea
ves the E698 band disappeared almost completely from the excitation sp
ectrum and a pronounced decrease of the efficiency of energy transfer
from Chl b to fluorescing Chl a occurred both within PS II and PS I. T
hese findings support the relation between the appearance of E698 in t
he excitation spectrum of Chl a fluorescence originating from LHC I an
d a high functional integrity of LHCs. (C) 1997 Elsevier Science S.A.