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Bruskova R. K. Zartdinova R. F. Satskaya M. V. Izmailov S. F. 《Russian Journal of Plant Physiology》2004,51(5):631-635
The organ topography of sucrose synthase and soluble acid invertase in pea seedlings at heterotrophic stage (3–14 days) was studied. Sucrose synthase was most active in the roots, with the highest activity on the 6–8th days. In the leaves, its activity decreased from day 3 to day 14. In the stems, sucrose synthase activity was at an invariantly low level. The patterns of sucrose synthase activity in etiolated and green plants were similar. As distinct from sucrose synthase, invertase activity was the highest in the stem, especially in etiolated plants. The peak of its activity was observed on the 6-8th days. In the leaves, invertase activity was lower but its pattern was the same. In the roots, acid invertase activity decreased from the 3rd day and did not depend on illumination. The conclusion is that differences in sucrose synthase and acid invertase activities in roots, leaves, and stem are determined by differences in the import of hydrolytic products of stored compound from the cotyledons as well as by different demands of these organs for these products for the processes of organ expansion and for the maintenance of organ metabolism. 相似文献
2.
S. F. Izmailov V. P. Piskorskaya R. K. Bruskova A. M. Smirnov 《Biologia Plantarum》1982,24(4):241-247
An investigation has been carried out to find out in what compounds carbon is radially transported from stele to the cortex
and to study sucrose metabolism in the root. These tissues were fed with14C-sucrose either directly or through the mesocotyle. In the latter case, the bulk of radioactivity, both in the stele and
cortex, was concentrated in sucrose rather than in mono saccharides. This corresponds to the radial transport of carbon from
stele to cortex predominantly in the form of sucrose. In the case of a direct exposure of stele and cortex,14C-sucrose was utilized for respiration, amino acid biosynthesis, and accumulation of carbon in the form of glucose. The hydrolysis
of sucrose to the monosaccharides and subsequent utilization of the latter in respiration was more intensive in the stele.
In the cortex, the sucrose carbon was more actively used for amino acid synthesis, owing to a high concentration of nitrate
reductase, glutamate dehydrogenase and glutamine synthetase. It was concluded that the cortex is the main issue zone providing
nitrogen assimilation in the root. 相似文献
3.
Davydova M. A. Bruskova R. K. Gazizov I. S. Izmailov S. F. 《Russian Journal of Plant Physiology》2002,49(5):614-621
The activities of glutamate dehydrogenase, asparagine synthetase, and total glutamine synthetase in the organs of the white lupine (Lupinus albus L.) plants were measured during plant growth and development. In addition, the dynamics of free amino acids and amides in plant organs was followed. It was shown that the change in the nutrition type was important for controlling enzyme activities in the organs examined and, consequently, for directing the pathway of ammonium nitrogen assimilation. As long as the plants remained heterotrophic, glutamine-dependent asparagine synthetase of cotyledons and glutamine synthetase of leaves apparently played a major role in the assimilation of ammonium nitrogen. In symbiotrophic plants, root nodules became an exclusive site of asparagine synthesis, and the role of leaf glutamine synthetase increased. Unlike glutamine synthetase and asparagine synthetase, glutamate dehydrogenase activity was present in all organs examined and was less dependent on the nutrition type. This was also indicated by a weak correlation of glutamate dehydrogenase activity with the dynamics of free amino acid and amide content in these organs. It is supposed that glutamine synthetase plays a leading role in both the primary assimilation of ammonium, produced during symbiotic fixation of molecular nitrogen in root nodules, and in its secondary assimilation in cotyledons and leaves. On the other hand, secondary nitrogen assimilation in the axial organs occurs via an alternative glutamate dehydrogenase pathway. 相似文献
4.
R. K. Bruskova A. V. Nikitin M. V. Satskaya S. F. Izmailov 《Russian Journal of Plant Physiology》2009,56(1):74-79
The in vivo and in vitro nitrate effects on pea (Pisum sativum L.) sucrose synthase (SS) were studied. At the period of plant transition from heterotrophic to autotrophic nutrition, exogenous nitrate (14.2 mM) absorbed in the form of KNO3 and Ca(NO3)2 during 10–20 days activated SS in the roots by 22–100% as compared with plants grown on nitrogen-free medium. Such effect was observed only at plant growing under high light (natural illumination up to 25 klx) and thus their sufficient supplement with sucrose. Under low light (climate-controlled chamber, 2.5 klx), nitrate could not activate SS. In the in vitro experiments, nitrate activated SS exponentially by a dose-dependent mode with the plateau at 3–5 mM, where its activity was increased by 50%. It is supposed that there is a second constituent in SS activation by nitrate, and it carries information about plant carbohydrate status. Possible mechanisms of nitrate-induced SS activation are discussed. 相似文献
5.
S. F. Izmailov R. K. Bruskova S. A. Chechetka S. V. Kirnos T. A. Nikiforova M. V. Satskaya 《Biology Bulletin》2003,30(2):140-148
Low nitrate assimilation activity of the root nodules was demonstrated by assaying the activities of nitrate reductase, glutamate synthetase, glutamate dehydrogenase, and asparagine synthetase as well as the kinetics of 14C-labeled sucrose incorporation in the amino acids and amides of the cortex and the bacteroid-containing root nodule zones. Irrespective of the exogenous nitrogen concentration (0, 11.2, or 25 mM NO-
3), nitrate concentration in the nodules was low as compared to the plant roots, leaves, and stems. This allowed us to propose the presence of structural and/or metabolic barriers in the nodules limiting nitrate transport and assimilation in the nodule. 相似文献
6.
S. F. Izmailov V. P. Piskorskaya R. K. Bruskova A. M. Smirnov 《Biologia Plantarum》1982,24(4):254-259
Roots obtained from 4-day maize seedlings were allowed to absorb uniformly labelled14C-suorose only with their middle part while the apical and basal parts did not contact the medium. The amino acids and their
amides produced in the cortex at the expense of nitrates and the14C-sucrose carbon moved radially to the stele where they were selectively distributed in the polar directions of transport.
“Primary” amino acids moved predominantly in the apical direction while amides and basic amino acids were transported mainly
in the opposite direction. When the nutrient medium was devoid of nitrogen sources, the amino acids entering the stele from
the cortex were transported mostly to the root tip, indicating a significant role of young tissues in consuming organic nitrogen
compounds when they are in short supply in the root. 相似文献
7.
S. F. Izmailov V. P. Piskorskaya R. K. Bruskova A. M. Smirnov 《Biologia Plantarum》1982,24(4):248-253
The radial transport of organic nitrogen compounds was studied in maize seedling roots in relation to the metabolism of uniformly
labelled14C-amino acids (alanine, arginine, dicarboxylic amino acids and their amides) in the cortex zone. Most active metabolism accompanying
transport to the stele was observed for14C-glutamic acid of “primary” amino acids and for14C-glutamine of “reserve” nitrogen sources. The transport of14C-asparagine and14C-arginine to the conducting bundles is accompanied by weak metabolism. A distinguishing feature of nitrogen metabolism in
the stele is intensive decarboxylation of glutamic acid, formed in the course of radial transport and metabolism, to gamma-amino
butyric acid. This process is assisted by a highly active glutamate decarboxylase present in the conducting bundles. 相似文献
8.
A. V. Nikitin R. K. Bruskova T. M. Andreeva S. F. Izmailov 《Russian Journal of Plant Physiology》2010,57(1):69-73
The effects of ammonium on activity of sucrose synthase (SS) in the roots of pea (Pisum sativum L.) plants were studied. On the medium containing 14.2 mM (NH4)2SO4, SS activity increased by 20–200% for 10–20 days of plant growth as compared with the roots of plants growing without nitrogen.
Illuminance affected the degree of effects. Under natural illumination, ammonium affected SS activity not only in sunny days
(up to 25 klx) but also in cloudy days (3–6 klx) but to a lower degree. Under stable low light (2.5 klx), ammonium did not
affect SS activity. In the in vitro experiments, at (NH4)2SO4 concentrations from 0 to 1 mM, SS activity was suppressed (up to 10%), whereas 1–37.5 mM (NH4)2SO4, it was increased (up to 50%). 相似文献
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