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CO2 on the roots part 2


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Doklady Akademii Nauk SSSR
1951. Vol. 79, No 4


A.L. Kursanov, A.M. Kuzin and Y.V. Mamul


It has been 170 years since the discovery of CO2 assimilation of green plants. (1)
Since then numerous articles connected to this problem have appeared, most of them regarding the effects of inside and outside conditions on the intensity of plant photosynthesis.
It was by these means that biologists and agronomists increased insight in the productivity of the plants they cultivated, and found methods for the increase of this productivity.
In many of these works much attention has been paid tot the fixation of CO2 and consequently to the entire process of air nutrition” of plants.
Meanwhile, many kinds of soil, especially carbonate soil, have a great amount of free and bound carbonic acid that may be probably by the plant roots together with a soil solution.

In account of the fact, tat the water motion in the plant, caused by the transpiration, is performed towards the leaves, and that this process takes place especially in the day time, we can assimilated by the plant, just like the other, that diffuses in the leaves from the air.

The specific gravity of each of these CO2 sources will change depending on the conditions. But, undoubtedly, in a number of cases the carbonic acid introduction through the root may become the vital source of carbon for the plants.
Unfortunately, the researchers almost didn’t study this second way of CO2 entering the plants.
As a result, today we only have single observations, and this phenomenon stays widely unexplored. (2-7)
Whereas, it’s expected, that the extra carbon acid feeding of the plants through the roots, especially by the agriculture with artificial irrigation, will greatly increase the plant productivity.
Nowadays this is indeed very interesting because of the rise of large irritation systems constructions, and the specific importance of agriculture with artificial irrigation in the USSR.
These considerations taken, the following research has been performed, using the modern isotope methods, to investigate whether CO2 can enter the plant through the roots, and also tot define the possibility of its assimilation by the green plant in light. The experiments had the purpose tot reveal the specific importance of CO2 as a source in the plant feeding.
For our research of carbon utilization from the carbonates of the soil solutions we used Knop’s feeding solution, which consisted of sodium bicarbonate with C14. The total amount of bicarbonate was 0,2%. The amount of radio active carbon was rather small. Such amount was taken on purpose- it was for the plants not tot be exposed. Therefore 10 ml of feeding solution contained only 0,5 µC.
30-old day common bean (Phaseolus vulgaris) has been used for the research. The plant roots were put into a wide test tube, with the feeding solution, with the stem starting at the plug. Which hermetically locked up the tube. This system excluded the possibility of radioactive CO2 to the atmosphere in which the stem and the leaves were. The plant was placed under the lamps of 300 Watt, with a distance between the plant and the lamps of 20 cm. After a three-hour experiment under the lamps one leaf was removed, and in 18 hours the experiment was over. The plant material has been washed in running water for 10 minutes, after which it was dried in between filter paper sheets.
According tot the results of the autoradiography we obtained the following scheme, shown on the picture 1 (see attachment).
On the autoradiography results it is seen that all parts of the plant contain the radioactive carbon: The greater amount of it is in the stem, and the less is in the leaf. The leaf, which had been removed form the plant, 3 hours after the research had been started, didn’t contain any radioactive carbon. To define the magnitude determination the leaf, the stem and the root were separately pounded and the relative activity was determined on the end-window counter (we took 10 mg of tissue on the disk with the radius of 2 cm). Having the purpose tot determine what part of the radiation was induced by the absorbed carbonates, we heated the tissues together with the 10% of hydrochloric acid, then we dried it in vacuum and again tested their activity. The results of this process are shown in table 1.

As it is seen, the quantity of assimilated carbon in the stems (the stems, which were taken, are rich of chlorophyll) is twice larger than the quantity in the roots, while these amounts will not change if we use the hydrochloric acid. This suggests the transformation of the carbonates non-volatile organic substances. We had tot demonstrate, that the plant used the absorbed CO3- ions in a same manner as CO2 from the atmosphere, ore that they took part in photosynthesis. Therefore we repeated our experiments, at that one plant had been lighted for 10 hours, and another plant had been kept in the dark. The auto radiographies of these plants are represented on pictures 2 and 3.
These auto radiographies demonstrate that during the period of 10 hours the absorbed carbonates are not assimilated in the stem during the dark, but in the light carbonates are stored in the tissues of the green stem, so it’s discovered higher in the stem, where the stem is of green colour, although within the parts without chlorophyll (the stem-part close tot the root), the carbon is not following experiment, where of the CO3- disclose on the photosynthesis is observed more clearly in the marked carbon, had been in light for 5 hours, then the half of the leaf was taken and was tested. After this the plant had been in the dark for the whole night and then the second part of the leaf was found and the plant had been lighted for 3 hours and only after this the whole plant was found. The received auto radiographies are on picture 4.
As it is seen from the auto radigraphies, after the 5 hours of light the carbonates didn’t come to the leaves yet. And as it goes from the previous experiment, they are actively absorbed by the green stem. For the night of being in the dark the carbonates are built up in the leaf- the amount of them is still rather little. But we can already see the feeble stamp of the half of the leaf. The further lighting runs tot the active assimilation of the absorbed carbonates that is distinctly seen by the intense radiation of the third leaf. Just to become certain that the coming through the roots carbonates are assimilated by the plant the same way CO2 is, that is they turn to the carbohydrates, we isolate them from the plant, being given of labelled carbon through the roots for 24 hours. The pounded dried plant (the stem and the leaf) had been boiled for 30 minutes with 1 N of hydrochloric acid. The received muriatic extract was run through the anionite and cation to eliminate the acids and the bases, then was concentrated in vacuum and to this solution 100 mg of chemical glucose, as a carrier, was added. After glucose had been dissolved, it was precipitated with phenylhydrazine. Precipitation of osazone looking like bunches of needles, was isolated, flushed up and recrystallized from the aqueous alcohol. Its activity is 112 imp/min. (10 mg on the disk of diameter 2 cm). Osazone had been recrystallized from the aqueous alcohol for 5 times. The activity was 100 imp/min under the same conditions. Osazone activity points out the activity of carbohydrates, which is the formation of the carbohydrates from the carbonates, given tot the plant trough the roots.
The conducted experiment showed, that the soil carbonates can be assimilated as much as CO2 of the air.

The Institute of Biochemistry of A.N. Bakh and the laboratory of biophysics and isotones and radiance of the Academy of Sciences of USSR.

1 J. Ingen-Housz, Esperiments upon Vegetables, London, 1779.
2 M. Bergamaxchi, Atti Inst. Bot. Univ. Pavia, 4, 1, 117 (1929).
3 E.A. Livingston and R. Bealf, Plant Physiol., 9, 237, (1934).
4 O. Overkott, Zs. F. Gesamt. Aturwiss., 3, 480 (1938).
5 O. Hartel, Jahrb. Wiss. Bot., 87, 173 (1939).
6 V. Kudrevich, Sov. Bot., 1, 70 (1940).
7 R. Overstreet, S. Ruben and T. Broyer, Proc. Natton. Acad. Of Sciences, 26, 688 (1940)

Still the plants possessed the higher efficiency index (Table 2):
Sugar beet efficiency index depending on CO2 nutrition (average per 1 plant, U- 752stain)

The date of economic parameters increase, given in Table 2, shows, that CO2 nutrition increases the root weight, gain rate and sugar content, but under these conditions the absolute and relative amount of leaves is reduced. It suggests of intensive photosynthesis in assimilation ability in the plants that received CO2 nutrition in comparison with nil treatment samples, providing the larger root weight, but the smaller leaf area (Table 1) and leaves weight (Table 2). It increased the assimilation apparatus efficiency (Table 3).

Reference tot Table 3 shows, that a leaf area unit of the plants, receiving CO2 nutrition, and accounts for larger root weight, than in the nil treatment sample. It was not observed only on the initial stage, probably due to the young age of plants and smaller leaf area, that prevented them from utilizing all the additional carbonic acid, though the assimilated it, as the carbon content in leaves suggests (Table 4).The carbon content was defined by the Turin-Lukashik’s method in middle samples of leaves gathered in the morning (9-12 a.m.), fixed with steam and dried until air-dry condition.

Reference to Table 4 shows, that carbon content in the plants receiving CO2 nutrition, is 7-9% higher than in the nil treatment samples that indicates the better conditions of organic substances synthesis. Only on June, 9 the carbon excess is 30%, probably due to the fact, that the sample included young leaves only (there have been no old ones yet). The entire following test included mainly old leaves, depending on their amount on the plant. The carbon content was checked in leaves as well as in the roots by the same method (Table 5):

Reference to Table 5 shows that the CO2 nutrition has been increased the carbon content in roots as well. The noted increase of leaves photosynthesis influenced the sugar beet crops per hectare (Table 6), (the crops were harvested on October 7-9, 1953).
Reference tot Table 6 shows, that carbonates nutrition has increased the root crops by 16.2 % (85 centres per hectare) and sugar yield by 14.5% (12 centres per hectare) in comparison with the leaves amount and sugar content practically the same as in nil treatment samples. But together with root crops growth, the weight of the crops has significantly reduced during the vegetation period. As a result of CO2 nutrition, the photosynthetic rate of the plants has increased (as demonstrated by the relation of root weight tot leaves weight), the assimilation apparatus area has reduced as well as the leaves weight, while the daily average root gain has increased.
The noted changes of the sugar beet growth dynamics are of particular importance in Latvia, where the leaf area growth and its efficiency in increasing for the whole period of vegetation, being a favourable condition for carbonic acid application, which boost the photosynthesis process.
Thus, the results, received in the 1st year of experiments make it possible to suggest, that carbon nutrition may become an important factor of the sugar beet (and, probably, of other plants) crops growth and can be regulated as well as other nutrition conditions (N, P, K etc).

Presented on March 29, 1954

1. Kursanov A.L., Krukova N.N., Vartapenan B.V., Dokladi Akad. Nauk SSSR. 85, #4 (1952)
2. Kursanov A.L., Kuzin A.M., Mamul J.V., Dokladi Akad. Nauk SSSR, 79, # 4 (1951)
3. Kuzin A.M., Merenova V.I., Mamul J.V., Dokladi Akad. Nauk SSSR, 85, # 3 (1952)
4. Lukashik N.A. TSHA report, 10 (1049)
5. Nicjiporovich A.A. “Breeding and seed forming”, # 2 (1953)
6. Samokhvalov G.K.
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