THE SUSCEPTIBILITY OF PS-II OF LOLIUM-PERENNE TO A SUDDEN FALL IN AIR-TEMPERATURE - RESPONSE OF PLANTS GROWN IN ELEVATED CO2 AND OR INCREASED AIR-TEMPERATURE/
M. Bartak et al., THE SUSCEPTIBILITY OF PS-II OF LOLIUM-PERENNE TO A SUDDEN FALL IN AIR-TEMPERATURE - RESPONSE OF PLANTS GROWN IN ELEVATED CO2 AND OR INCREASED AIR-TEMPERATURE/, Environmental and experimental botany, 39(1), 1998, pp. 85-95
The effect of a sudden fall in air temperature from 20 to 5 degrees C
on fast kinetics of chlorophyll fluorescence, maximum yield of the pho
tosystem II photochemical reactions (Fv/Fm), quantum yield of the phot
osystem II electron transport (Phi(II)) coefficients of photochemical
(qP), non-photochemical quenching (qN) was studied in Lolium perenne u
sing a modulated chlorophyll fluorescence technique. Before fluorescen
ce measurement, the plants were cultivated in the treatments simulatin
g the likely future climate characterized with elevated air temperatur
e and CO2 concentration and combination of both. On fast kinetics curv
es the risetimes of the I and D points characterizing the redox state
of Q(A) were affected by lowering the air temperature. At 5 degrees C
both the I and D points were reached later than at 20 degrees C. Also
the I to D risetime was prolonged at 5 degrees C and it was found sign
ificantly longer in plants cultivated in ambient + 4 degrees C tempera
ture. While a significant difference was found in the area over the ri
sing part of the fluorescence curve between 20 and 5 degrees C, no dif
ference was found in area over the relaxation curve part. Lowering of
air temperature to 5 degrees C had no effect on Fv/Fm values in contro
l plants and in the plants cultivated in elevated CO2 but brought sign
ificant decrease in plants cultivated in the ambient + 4 degrees C air
temperature. Both Phi(II) and qP decreased with the temperature lower
ed to 5 degrees C while the values of qN increased. The changes in flu
orescence parameters indicated altered functioning of PS II at low tem
perature. The changes in parameters are discussed as a consequense of
decreased enzymatic activity, decreased turnover of plastoquinone pool
and photoinhibition. (C) 1998 Elsevier Science B.V. All rights reserv
ed.