1021-4437/02/4906- $27.00 © 2002
Russian Journal of Plant Physiology, Vol. 49, No. 6, 2002, pp. 715–722. Translated from Fiziologiya Rastenii, Vol. 49, No. 6, 2002, pp. 805–813.
Original Russian Text Copyright © 2002 by Bulychev, Cherkashin, Rubin, Müller.
The proton transport across the plasma membranes
underlies many functional processes in the plant cell,
such as electrogenesis [1–3], turgor regulation [4, 5],
polar transport, and growth and development . The
pH levels in the cytoplasm and the outer medium affect
the activities of membrane systems, the functioning of
ionic channels [5, 7], and permeation into the cell of
neutral and charged forms of protonated substances .
Therefore, a great deal of attention is focused on the
regulation of H
transport across the plasma mem-
branes and the formation of membrane domains with
-transporting activities [8, 9]. The cells of
characean algae are of particular interest, because the
membrane transport of H
) in illuminated cells
strongly varies along the length of an internode [10, 11].
In dark-adapted characean algae, the properties of
the plasmalemma are uniform over the cell surface.
However, illumination results in a comparatively fast
transition (within 10–20 min) from a homogenous state
to a spatially separated distribution of transport systems
. Thus, alternating regions of low and high pH (acid
and alkaline zones, respectively) arise in the vicinity of
the cell surface, with electric currents ﬂowing between
these regions. The origin of the transmembrane cur-
rents is not known with certainty, because the vibration
electrode technique, used for detecting these currents,
does not discriminate between particular ion ﬂows.
Nevertheless, the majority of authors believe that the
acid zones represent membrane regions with actively
functioning proton pumps [13, 14], whereas the alka-
line zones correspond to the domains where the high
pH channels are activated [15, 16].
The heterogeneous distribution of H
systems is closely related to other cellular processes.
For example, the photosynthetic activity of chloro-
plasts, which constitute a thin layer on the periphery of
the cytoplasm, varies in spatial coherence with the loca-
tion of acid and alkaline zones . Measurements of
ﬂuorescence parameters of chloroplasts exposed to
actinic illumination and saturating light pulses showed
that the photochemical activity of photosystem II in the
acid zones is higher than in the alkaline zones .
In order to understand the origin of the spatial distri-
bution of H
membrane transport, it is necessary to
monitor the dynamics of acid and alkaline bands during
Distribution of Acid and Alkaline Zones on the Cell Surface
under Stationary and Local Illumination
A. A. Bulychev*, A. A. Cherkashin*, A. B. Rubin*, and S. C. Müller**
*Department of Biophysics, Faculty of Biology, Moscow State University, Vorob’evy gory, Moscow, 119899 Russia;
fax: 7 (095) 939-1115; e-mail: email@example.com
**Institute of Experimental Physics, Otto-von-Guericke University, Magdeburg, D-39106 Germany
Received March 26, 2002
—A scanning microprobe technique was used to study pH distribution near the cell surface of
Klein ex Willd. under variations of light intensity, dark–light transitions, and local illumination of var-
ious cell parts. In darkness, the H
-transporting activity of plasmalemma was distributed homogeneously over
the cell surface. However, after exposing the cell to weak light (irradiance 0.2–0.5 W/m
), individual alkaline
pH of 1–2 units were observed in the longitudinal pH proﬁle. The peaks in the longitudinal pH
proﬁle became more numerous with the increase in light intensity. The plot of
pH as a function of light inten-
sity included a steep transition from zero to its maximum amplitude. In strong light (100 W/m
), the pH bands
alternated along the cell length with a periodic length of about 7 mm. It is shown that the light-induced forma-
tion of ring-shaped bands with H
-exporting and H
sink activities is preceded by the appearance of irregularly
located spots (patches). When small cell parts were illuminated and the light spot was suddenly shifted along
the cell to another position, the alkaline bands reorganized in two ways. In some cases, this treatment was fol-
lowed by a gradual shift in the band position (without attenuation in the peak height) toward the illuminated
area. In other cases, the initial band disappeared after such treatment, and a new alkaline band emerged in the
vicinity of the illuminated area. Despite the apparent similarity of regular bands in the longitudinal pH proﬁles,
the properties of individual bands (variable sensitivity to light intensity changes, the ability of bands to move
along the cell under external treatment) differ substantially. It is supposed that the light-induced formation of
the pH proﬁle is based on primary ﬂuctuations of photosynthetic and transport activities in the chloroplast layer
and the plasmalemma, as well as on further rearrangements of membrane domains that stabilize band locations.
Key words: Chara corallina - acid and alkaline zones - proton ﬂuxes - photosynthesis - light intensity - structure