Root Nodules Of Leguminous Plants Research Articles

Structure of leghaemoglobin from lupin root nodules at 5 angstrom resolution.

THE similarity in tertiary structure of mammalian haemoglobins1–3 and myoglobins4,5 and of haemoglobins from invertebrates6,7 shown by X-ray analysis has been particularly important for our understanding of the biological evolution of these proteins. We have therefore studied the structure of leghaemoglobins—plant haemoglobins found in root nodules of leguminous plants—and compared the structures of seemingly unrelated, in terms of evolution, haemoglobins.

Biosynthesis of Hæmin in Soy-bean Nodule Homogenates

IT has been shown that root nodules of leguminous plants contain a haemoprotein with a prosthetic group indistinguishable from protohaemin IX of haemoglobin1. Elucidation of the mechanism of formation of this pigment in plant material should broaden our knowledge of biosynthetic reactions leading to the formation of porphyrins, and make it possible to compare haemin synthesis in plant and animal tissues.

Reduction of Hydroxylamine in the Root Nodules of Leguminous Plants.

Reduction of Hydroxylamine in the Root Nodules of Leguminous Plants.

Studies on the Assimilation by the Host Plants of Nitrogen Fixed in the Root-Nodules of Leguminous Plants.

Studies on the Assimilation by the Host Plants of Nitrogen Fixed in the Root-Nodules of Leguminous Plants.

Free Amino-Acids in the Leaves, Roots and Root Nodules of the Alder (Alnus)

AN intensive fixation of atmospheric nitrogen takes place not only in the root nodules of leguminous plants but also in those of the alder1. For example, in a quartz sand culture of Alnus glutinosa with no combined nitrogen the growth was 261 cm. in length and the increase of nitrogen in the plant about 6.5 gm. in the second year (Virtanen and Saubert-v. Hausen). In order to gain information on the mechanism of the atmospheric nitrogen fixation and the nitrogen metabolism in general we have examined the seasonal occurrence of free amino-acids in the different parts of A. glutinosa and A. incana.

荳科植物根瘤のラクトフラビン

The root-nodules of leguminous plants were found to be extremely rich in lactoflavin content as compared with other parts of the plants. The average content was 14.6mg% in dry matter (3.6mg% in fresh tissue) for soybean nodules as shown in Table 1. By careful preparation of the material, the lactoflavin was detectable both in cell-extract (mixture of protoplastha and cell-sap) and bacteria. But the lactoflavin in the bacteria easily disap-peared on extraction with water or Ringer solution, the non-extractable part amounting only to 2.04mg% of dry matter. The most part of the Iactoflavin in the nodules existed in free state. No phosphoric ester or proteid was found in the cell-extract of the nodules.

The concentration and distribution of haemoglobin in the root nodules of leguminous plants

The concentration and distribution of haemoglobin in the root nodules of leguminous plants

HÆMOGLOBIN AND NITROGEN FIXATION IN THE ROOT NODULES OF LEGUMINOUS PLANTS

IT has been shown by Kubo1 that the root nodules of leguminous plants contain a haemoprotein compound resembling haemoglobin and probably acting as a store as well as a carrier of oxygen. The haematin nature of this pigment was confirmed by Burris and Haas2, who believed, however, that it was not a haemoglobin-like compound which could undergo oxygenation, but rather an oxido-reduction catalyst in which the iron changes its valency. That this pigment is a true haemoglobin was demonstrated by Keilin and Wang3, who purified it and found that : (1) it forms a perfectly reversible compound with molecular oxygen ; (2) it has a high affinity for oxygen, the p50 at 15° being less than 0.1 mm. mercury ; and (3) the relative affinity of this pigment for oxygen and carbon monoxide in terms of the equilibrium constant K = [HbCO] [p02]/[Hb02] PpCO] is about 37 at 15° C. They also determined the spectrophotometric absorption curves of this haemoglobin and of its compounds with oxygen and carbon monoxide.

XXIV.—The Occurrence of Endodermis in Leguminous Root Nodules and Its Effect upon Nodule Function

In recent years considerable progress has been made in the investigation of the biochemistry and physiology of the root nodules of leguminous plants (Wilson, 1940). It now appears desirable that the anatomical structure of the nodule should be re-examined from the standpoint of the functions which the nodule is considered to discharge. Special interest attaches to the distribution within the nodule of endodermis, cork, and any other suberized layers, since on this will depend the facility with which materials may be exchanged between the tissues of the nodule and the environment. There is some confusion in the literature as to the distribution of such suberized tissues within the nodule, but it is clear that rather curious features are presented.

Excretion from Leguminous Root Nodules

IN previous communications1,2,3, I have reported my inability to detect appreciable excretion of nitrogenous substances from root nodules of leguminous plants, and thus to confirm the results obtained by Virtanen. During the past summer, further trials have been carried out with soya bean (4 varieties), pea (5 varieties), and broad bean. Three rooting media have been employed, namely, (a) a coarse quartz sand composed of particles of diameter mostly in the region of 0.5 mm. ; (b) a fine quartz sand of particles diameter 0.1–0.3 mm. ; and (c) a very fine quarry sand of particles 0.1 mm. and less, (b) appears to be very similar to the sand used by Virtanen. Open and closed containers have been used, while the tests for excretion consisted of analysis of rooting medium and of barley plants grown in association with the legumes.

Excretion of Amino Acids from the Root Nodules of Leguminous Plants

AFTER having shown that amino acids appear in the medium in inoculated, but otherwise sterile, quartz sand cultures of leguminous plants, we assumed that these amino acids are excreted from the nodules. The experimental evidence then available did not, however, exclude the possibility that the excretion might be a function of the roots.

Excretion of Nitrogenous Compounds from the Root Nodules of Leguminous Plants

THE activities of the nodule, and particularly the excretion of nitrogenous compounds from the nodule into the medium, are largely dependent upon the supply of air to the roots. The quantity of excreted nitrogenous compounds is the greater the larger the culture flask. This fact has been clearly demonstrated by our experiments with sterile cultures of inoculated peas in quartz sand. The results also showed that the rate of excretion is proportionally highest at an early stage of development of the plants when the nodules are still quite young. Hence it can be concluded that the passage of the nitrogen compounds into the sand actually is due to excretion and not to a decomposition of the nodule proteins.

The Occurrence of Urease

LETTERS on the occurrence of urease are printed in NATURE of August 11 and September 22. In the former, Prof. Werner reports that he has found urease in all the leguminous nodular growths he has tested; in the latter, Prof. Beijerinck describes how he has detected the enzyme in B. radicicola. Prof. Werner writes: “So far as we have been able to ascertain, the peculiar root nodules of leguminous plants have not hitherto been tested for urease.” I reproduce, therefore, the following passage from an article on “The Function of Hormones in regulating Metabolism,” by my son and myself, published in the Annals of Botany, vol. xxv., No. xcviii., April 1911.

The Importance of the removal of the Products of Growth in the Assimilation of Nitrogen by the Organisms of the Root Nodules of Leguminous Plants: A Preliminary Note

For nearly eighteen years the problem of the fixation of nitrogen by the root nodules of leguminous plants has been the subject of investigation by numbers of workers in many parts of the world, and steady progress has been made towards realising the conditions under which the organism works in the nodule. Artificial nutrient media have been prepared closely resembling the food supplied by the plant, and the organism itself has in recent years been induced to grow in artificial culture in the characteristic “bacteroid” forms approximating to those which are found in nature.