ISSN 1021-4437, Russian Journal of Plant Physiology, 2006, Vol. 53, No. 1, pp. 96–101. © MAIK “Nauka /Interperiodica” (Russia), 2006.
Original Russian Text © T.V. Veselova, V.A. Veselovsky, 2006, published in Fiziologiya Rastenii, 2006, Vol. 53, No. 1, pp. 106–112.
Seed deterioration during their ageing is accompa-
nied by the increased membrane permeability for water,
electrolytes, and other cell metabolites [1, 2]. A rapid
water uptake by aged seeds brings the threat of their
damage during imbibition [3–5]. In legume seeds,
embryo hypoxia can arise under these conditions [6, 7].
As a result, some seeds perish. Other seeds germinate,
but the seedlings can manifest morphological defects
due to post-hypoxic oxidative stress .
Many researches believe that an increased perme-
ability of the plasma membranes during ageing is due to
some changes in physical properties of the lipid bilayer
resulting from phospholipid hydrolysis and free radical
oxidation of unsaturated fatty acids (FAs) [2, 9, 10]. A
gel phase appears in the liquid–crystalline structure of
the membrane, interfering with the interaction between
membrane proteins and lipids; ions and metabolites
leak between these gel domains of the bilayer. True,
other researchers do not agree with this hypothesis.
Thus, Priestley and Leopold  could not ﬁnd any
changes in FA unsaturation during soybean seed age-
ing. The products of membrane lipid peroxidation were
detected only in seeds that completely lost their capa-
bility of germination . The changes in the physical
state of the lipid bilayer were noticed in liposomes pre-
pared from lipids of seeds with germinability dropped
from 93 to 16% . Therefore, some authors believe
that changes in lipids during ageing are a postmortem
process, i.e., lipid peroxidation is rather a consequence
than a cause of membrane damaging [12, 13].
Earlier we observed that, after 5 to 7 days of accel-
erated ageing (at 40
C and 85% relative humidity),
some seeds appeared, which imbibed much more rap-
idly than before ageing, and germinability of a seed lot
increased. However, the seedlings grown from these
seeds had morphological defects, which lowered the
quality of the seed lot. With ageing prolongation to
10 days, the proportion of rapidly imbibing seeds
Possible Involvement of Aquaporins
in Water Uptake by Pea Seeds Differing in Quality
T. V. Veselova and V. A. Veselovsky
Faculty of Biology, Moscow State University, Vorob’evy gory, Moscow, 119899 Russia;
Received April 11, 2005
—Using the method of room temperature phosphorescence (RTP), we divided air-dry pea (
L.) seeds subjected to accelerated ageing (40
C, 85% relative humidity) into three fractions: (I) high-
quality seeds, (II) weakened seeds, and (III) dead seeds. In the process of ageing, seed germinability ﬁrstly
decreased and then increased due to so-called “improved” seeds of fraction II, which returned to fraction I as
judged from the RTP level; the germinability of these seeds became equal to that of fraction I seeds. Seeds capa-
ble of germination (fractions I and II) differed in the rates of imbibition, which depended on plasma membrane
permeability (opened or closed water channels) but not on the presence of the seed coat. A low activation energy
of seed imbibition in fraction II (less than 5 kcal/mol) indicates that water channels are open. A mercury-con-
taining compound (5
-chloromercuribenzoate (PCMB) reduced the rate of water uptake by these seeds,
and dithiothreitol restored it. A high activation energy of fraction I seed imbibition (more than 12 kcal/mol) cor-
responded to the water uptake mainly across the lipid bilayer when water channels are closed. PCMB did not
affect the rate of fraction I seed imbibition. We supposed that mature air-dry pea seeds had open water channels.
During the ﬁrst stages of fraction I seed imbibition, these channels were closed, limiting water uptake. NaF
M), an inhibitor of phosphatase, prevented channel closing and accelerated the imbibition of fraction I
seeds. It did not affect the imbibition rate of fraction II seeds, indicating their water channels to be opened.
However, NaF did not affect the water uptake of “improved” fraction II seeds as well. It seems likely that their
channels were closed during accelerated ageing but otherwise than via dephosphorylation. The results obtained
indicate the possibility of water inﬂow regulation in the weakened seeds via the state of aquaporins, which form
water channels in the membranes.
Key words: Pisum sativum - seeds - accelerated ageing - fractions of seeds differing in quality - aquaporins -
water channels - p-chloromercuribenzoate - dithiothreitol - NaF
: DTT—dithiothreitol; FA—fatty acid; PCMB—
chloromercuribenzoate; RTP—room temperature phosphorescence.