1021-4437/00/4706- $25.00 © 2000
Russian Journal of Plant Physiology, Vol. 47, No. 6, 2000, pp. 740–747. Translated from Fiziologiya Rastenii, Vol. 47, No. 6, 2000, pp. 843–851.
Original Russian Text Copyright © 2000 by Zavorueva, Ushakova, Volkova, Tikhomirov, Mogil’naya, Medvedeva.
Prolonged higher plant growing under various PAR
spectra showed species-speciﬁc plant responses to the
light quality and intensity [1, 2]. Such species speciﬁc-
ity is most pronounced under red-light irradiation and
less expressed, if at all, when plants are grown under
blue or green light .
At low red-light irradiance (12 and 24 W/m
plants do not signiﬁcantly respond to this treatment .
Changes induced by an irradiance of 50 W/m
reversible [4–6]. The efﬁciency of the red-light irradia-
tion is determined not only by its intensity but also by
the structure of the radiation spectrum .
Thus, when pea, wheat, tomato, and maize plants
were irradiated with high-intensity (about 100 W/m
and more) long-wave (600–700 nm) light of the line
spectrum, they maintained the structure and functional
activity of the photosynthetic apparatus and high pro-
ductivity. Under similar conditions, in radish and
cucumber plants, photosynthesis was considerably sup-
pressed and, in some cases, plants perished . Earlier
, we showed that, at an irradiance of 100 W/m
red PAR region isolated from the radiance ﬂux with a
line-structured spectrum (from mercury–lithium
lamps) exerted a stronger inhibitory action on cucum-
ber plants than did similar light obtained from lamps
with a smoothed line structure (DRI-2000-6). In older
cucumber plants (22-day-old) grown under red light
from DRI-2000-6 lamps, the rate of apparent photosyn-
thesis per gram of dry weight was even higher than
under white light, although plant weight was reduced.
It seems likely that, under red light, plant growth was
retarded at the beginning of the growth period. How-
ever, later, in the process of growth and development,
plants acclimated to these conditions, and metabolic
processes became more active than under white light.
The mechanisms underlying these phenomena are
obscure. They are apparently related to some changes
in the ﬁne chloroplast structure and the processes
occurring in these organelles.
MATERIALS AND METHODS
Nine- and 22-day-old pea (
L., cv. Sma-
ragd) and cucumber (
L., cv. Moskovskii
teplichnyi) plants were used.
Plants were grown in a hydroponics culture in con-
trolled growth cabinets with claydite as a substrate and
at an irradiance of 100 W/m
. The spectral region of
600–700 nm was isolated from the radiance ﬂux pro-
vided by a DRI-2000-6 lamp (Lisma-Electro, Russia)
with the aid of red cut-off KS-10 ﬁlters (
> 600 nm).
To minimize the differences in the infrared radiance
between white and red light, we used a water shield
(5 cm thick) and glass heat-shielding ﬁlters (Lisma-
Electro, Russia). Water ﬁlters adjusted the long-wave-
length transmission cut-off to 1200 nm for both treat-
ments, and glass heat-shielding ﬁlters reduced infrared
radiation to 20–30% of that of incident light.
The pigment content in an average sample from all
true leaves was estimated spectrophotometrically after
Fine Chloroplast Structure in Cucumber and Pea Leaves
Developed under Red Light
E. N. Zavorueva, S. A. Ushakova, E. K. Volkova, A. A. Tikhomirov,
O. A. Mogil’naya, and S. E. Medvedeva
Institute of Biophysics, Siberian Division, Russian Academy of Sciences, Akademgorodok, Krasnoyarsk, 660036 Russia;
fax: 7 (3912) 43-3400; e-mail: firstname.lastname@example.org
Received June 17, 1999
—Photosynthetic activity, the content of various photosynthetic pigments, and the chloroplast ultra-
structure were examined in the leaves of cucumber (
L.) and pea (
L.) plants of
different ages grown under red light (600–700 nm, 100 W/m
). In pea leaves tolerant to red-light irradiation,
chloroplast ultrastructure did not essentially change. In the ﬁrst true leaves of cucumber plants susceptible to
red-light irradiation, we observed a considerable increase in the number and size of plastoglobules, the appear-
ance of chloroplasts lacking grana or containing only infrequent grana, and stromal thylakoids. In the upper
leaves of 22-day-old cucumber plants, the chloroplast structure was essentially similar to that of the control
chloroplasts in white light, and we therefore suppose that these plants have acclimated to red light.
Key words: Pisum sativum - Cucumis sativus - pigments - ultrastructure - red light
Abbreviations and designations
: PAR—photosynthetically active
radiation; PS—photosystem; P700—a pigment of the reaction
center of PSI.