Аннотация:Stimulatory effect of HA on the plant growth and germination is well known. Nevertheless,
the mechanism of that effect is unknown, as well as the HA distribution in the plant tissues.
Recently, a new method of direct labeling of humic substances with tritium was developed that
allows producing labeled preparation completely identical in their properties to the native
preparations [1] and an opportunity to use the produced humics to study their behavior in living
cells of bacteria has been demonstrated [2]. The objective of the study was to estimate uptake
of HA by higher plants and to obtain direct evidence of HA penetration in higher plants vascular
system using tritium autoradiography.
Coal HA was isolated from potassium humate produced from leonardite (H/C 0.87; O/C
0.5; C/N 53; Mn = 2.1). Seedlings of wheat Triticum aestivum L. were used for the experiments.
Eight-day old plants were transferred into the vials containing 15 mL of HA at concentration
5 mg⋅L–1 with specific radioactivity 0.057 Curie⋅L–1. Three plants were used per one vial.
Absorption time was 24 hours. All the experiments were performed in five replications. The HA
distribution study in the plant was performed using tritium autoradiography. For the
microautoradiography studies, the sections from wheat shoots and roots was excised and fixed
in Navashin buffer according to [3]. Then plant samples were subjected to autoradiography. The
nuclear emulsion was used for microautoradiography. Labeled samples getting and purification
them from exchange position tritium were held under regulations of [1].
Obtained autoradiogram showed that HA intensely adsorbed on the root surface and
accumulated primarily in the cortex area. HA absorbed by plants arrive in the central cylinder
zone mainly from apoplast. In the central cylinders HA found in the xylem vessels, which
indicate a possibility of acropetally transport. It is important to note that the using of nuclear
emulsion allowed us to obtain a much better resolution. In this way the presence of HA in the
cortex was shown, as well as within the xylem vessels.
References.
1. Badun G.A., Chernysheva M.G., Tyasto Z.A., Kulikova N.A., Kudryavtsev A.V.,
Perminova I.V. A new technique for tritium labeling of humic substances. 2010. Radiochim.
Acta, 98:161-166.
2. Kulikova N.A., Perminova I.V., Badun G.A., Chernysheva M.G., Koroleva O.V.,
Tsvetkova E.A. 2010. Estimation of uptake of humic substances from different sources by
Escherichia coli cells under optimum and salt stress conditions by use of tritium-labeled humic
materials. Appl. Environ. Microbiol. 2010, Vol. 76, No. 18, p. 6223-6230.
3. NS Voronin Guide to laboratory studies on the anatomy and morphology of plants.
Moscow, Prosveschenie, 1981, 160s.