The effect of polymetallic contamination and concomitant treatment with brassinosteroids (homocastasterone or homobrassinolide) on barley plants and on the ion-exchange capacity of cell walls isolated from shoots and roots was studied. A decrease in the dry weight of roots, water content, and the proportion of the cell wall in them was observed under the influence of polymetals, but the addition of homocastasterone to the medium led to the restoration of these parameters almost to the control level. In the aerial part of plants, the influence of both polymetals and brassinosteroids on these parameters was weakly expressed. In the presence of homocastasterone, the content of demethylated carboxyl groups of polygalacturonic acid increased in the pectins of the cell walls of roots and leaves, which are the main binding sites for heavy metal ions in the apoplast. Thus, it can be assumed that treatment with brassinosteroids (homocastasterone) leads to a change in the composition and ion-exchange properties of the cell wall, which allows one to reduce the toxic effect of polymetals due to their immobilization in the apoplast.

Проведен сравнительный анализ накопления меди корнями растений вики нарбонской (Vicia narbonensis L.) и изолированными из них клеточными стенками. Установлено, что основным местом накопления ионов меди у интактных растений является корневая система, а клеточные стенки корней характеризуются высоким содержанием карбоксильных групп полигалактуроновой кислоты, что обуславливает их высокую связывающую способность в отношении ионов меди. Полученные результаты показывают, что основной стратегией защиты растений вики нарбонской от повышенных концентраций меди в окружающей среде является предотвращение накопления ионов этого металла в цитоплазме клеток корня путем депонирования их в клеточную стенку.

Potentiometric titration of weak base anionite (the degree of crosslinking was 12–16%) was performed within the pH range of 2–12 and NaCl concentration range of 0.1–1.0 mol/L. The maximum ionexchange ability against HCl does not depend on the solution ionic strength and is 6.50 ± 0.12 mmol/g of dry solid matter. It was shown that the process of acid–base equilibrium can be adequately described by the Gregor equation within the studied stock electrolyte concentration and pH ranges. Two type of groups were discovered in anionite. The ionization constants of these groups differ by three orders of magnitude. The existence of amino groups of different nature was proved by the data obtained by functional analysis; it was estimated that the acidity of these groups decreases as NaCl concentration increases.

Cell walls and chitin-glucan complexes isolated from uneven-aged components of the thallus of the Peltigera aphthosa lichen were studied. The mass fraction of the cell wall and chitin-glucan complexes increased with age, but the content of nitrogen in these structures decreased with age. The basal area of the thallus was characterized by the largest mass fraction of the chitin-glucan complex from the dry mass of the thallus; the apical area, by the largest mass fraction of chitin in the complex. It was demonstrated that in P. aphthosa, the degree of deacetylation of chitin in the complex (depending on the age) was 33 and 54% in the apical and basal areas, respectively. The suggested method of functional analysis of chitin-glucan complexes for the presence of free amino groups in them can be used for studying other lichenified fungi.

Research into ion-exchange properties of cell walls isolated from thallus of red seaweed Phyllophora crispa was carried out. Ion-exchange capacity and the swelling coefficient of the red alga cell walls were estimated at various pH values (from 2 to 12) and at constant ionic strength of a solution (10 mM). It was established that behavior of cell walls as ion-exchangers is caused by the presence in their matrix of two types of cation-exchange groups and amino groups. The amount of the functional group of each type was estimated, and the corresponding values of pK a were calculated. It can be assumed that ionogenic groups with pK a ∼5 are carboxyl groups of uronic acids, and ionogenic groups with pK a ∼7.5 are carboxyl groups of the proteins. Intervals of pH in which cation-exchange groups are ionized and can take part in exchange reactions with cations in the environment are defined. It was found that protein was a major component of cell wall polymeric matrix because its content was 36%.

Исследовали ионообменные свойства клеточной стенки кустистого лишайника Cladonia rangiferina (L.) F. H. Wigg. Для выделения клеточных стенок использовали живые части подециев, а также “молодые части”, которые представляли собой четыре верхних междоузлия подециев, и “старые части” (с 4-го по 8-е междоузлие). Получены зависимости ионообменной способности клеточной стенки от рН в диапазоне изменения рН 2–12 и постоянной ионной силе раствора 10 мМ. Установлено, что в трехмерной структуре клеточных стенок C. rangiferina содержались три типа ионогенных групп, которые определяют ионообменные свойства оболочек. Это аминогруппы с рКа 3, карбоксильные группы с рКа 7 и фенольные ОН-группы с рКа 10. Определены количество групп каждого типа и константы их ионизации и показано, что в клеточных стенках молодых частей количество аминогрупп и карбоксильных групп выше по сравнению со старыми частями подециев (в 1.5 и 2.0 раза соответственно). Установлено, что с возрастом изменялось содержание азота и доля деацетилированных аминогрупп в клеточных стенках от 34% (молодые части подециев) до 40% (старые части подециев). Показано, что у C. rangiferina N-ацетилглюкозамин и глюкозамин не являются основными мономерами полимеров клеточных стенок, так как и в слоевищах, и в изолированных из него клеточных стенках содержание общего азота составляло менее 1%.

The acid/base properties of the root cell wall of 10-day old etiolated wheat (Triticum aestivum I,.) seedlings grown in tap water (I) and 38-day-old green plants grown in 0.5 N Pryanishnikov solution (II) were investigated. The ion-exchange capacity of apoplast ionogenic groups (S) as a function of pH was investigated in a pH range from 2 to 12 at a constant ionic strength (10 mM). Based on Gregor's model, parameters of the qualitative and quantitative composition of the ionogenic groups of the cell wall were calculated. Results obtained with the use of statistical analysis showed that the applied mathematical model adequately describes the process of the acid/base equilibrium studied. The data indicate that four types of ionogenic groups which belong to amido (pK(a) similar to 3), carboxylic (pK(a) similar to 5 and 7.5), and phenolic (pK(a) similar to 10) groups are present in the cell wall structure. The group with pK(a) similar to 5 belongs to galacturonic acid. The apparent discrepancy between the pKs of polygalacturonic acid found earlier by Grignon and Sentenac (3.2-3.4) and those established in the present work is explained by the fact that those authors did not take into account the existence of another type of ionogenic group in the polymer structure of the apoplast. The walls of root cells of groups I and II did not differ in qualitative composition of the functional groups, as indicated by the similar values of their ionization constants. The cell wall structure of the samples tested differs in the amount of their carboxylic groups: in etiolated seedlings it was two times lower than in green plants.