Germination Of Wheat Grains Research Articles

Activity of enzymes involved in pyrimidine metabolism in the germinating wheat grains

Activities of carbamoyl phosphate synthetase, aspartate carbamoyltransferase, dihydro-orotase, dihydro-pyrimidinase, uracil phosphoribosyltransferase, uridine phosphorylase, uridine kinase and acid phosphatase were measured in extracts from wheat grains germinated for periods ranging from 0 to 48 hr. With the exception of uridine phosphorylase which appeared only 24 hr after initiation of germination, all these activities were detected in the dry grains. Activities concerned with the synthesis of pyrimidine ring de novo dropped at the onset of germination (0·5–2 hr) and increased thereafter gradually. Activities involved in the degradative pathway were maintained at a roughly constant level during the first 24 hr and rose considerably later on. The results are discussed in relation to the sequence of initiation of RNA and protein synthesis during seed germination.

Triglyceride mobilization in the germinating wheat grain.

Triglyceride mobilization in the germinating wheat grain.

The mobilization of macronutrient elements in the germinating wheat grain

During germination in wheat the macronutrient mineral elements (magnesium, calcium and potassium) are redistributed from the aleurone tissue to the developing seedling. The hydrolysis of phytin, the storage form of these minerals, by phytase appears to be initiated by hydration of the aleurone tissue. The hydrolysis and the subsequent mobilization of the mineral elements are promoted by a gibberellin from the embryo. The increased phytase levels that appear in the aleurone cells during germination are induced by certain nitrogen compounds, particularly glutamine. Indole acetic acid increases the efficacy of the glutamine. The induction process probably involves the activation of an inactive form of the enzyme.

Studies on the effects of certain salts on germination, on growth of root, and on metabolism

1. Criteria of germination of wheat grains on morphological, histological and physiological bases were studied and described to set a parameter for the assessment of germination capacity. 2. The effects of single salt solutions of NaCl, Na2SO4, KCl, K2SO4, MgCl2 and MgSO4 on germination of wheat grains were investigated, and it was found that: 3. The suppressive action of salts on germination could be attributed to their effect on metabolism and not to their osmotic action for the following reasons: 4. The suppressive action of the salts on germination could be attributed to the cations rather than to the anions.

Studies on the Pyrophosphorylases of Wheat

Adenosine diphosphoglucose and uridine diphosphoglucose pyrophosphorylase activities (class EC 2.7.7.9) were assayed radiochemically in ammonium sulfate fractions prepared from mature and germinating wheat grain. Both enzymes showed similar pH optima and metal ion requirements but differed markedly in their response to activation by d-glycerate 3-phosphate and inhibition by sulfate and phosphate.Their stability characteristics also differed greatly. While UDP-glucose pyrophosphorylase was very stable, ADP-glucose pyrophosphorylase rapidly lost activity in dilute solution and upon desalting on columns of Sephadex and was only partially stabilized when stored as a suspension in ammonium sulfate. Relatively high salt concentrations were required to maintain even short term stability. ADP-glucose and UDP-glucose pyrophosphorylases had apparent K(m) values for alpha-d-glucose 1-phosphate of 4.4 x 10(-5)m and 10(-3)m, respectively. In extracts from dry grain, the number of units of UDP-glucose pyrophosphorylase were about 30-fold greater than the number of units of ADP-glucose pyrophosphorylase. During germination, the activity of UDP-glucose pyrophosphorylase increased markedly in both the embryo and the endosperm, while ADP-glucose pyrophosphorylase fell slightly over the initial 4 days of germination.

Induction of lipase and phytase activities in the aleurine tissue of germinating wheat grains

Induction of lipase and phytase activities in the aleurine tissue of germinating wheat grains

Induction of lipase activity in the starchy endosperm of germinating wheat grains

Induction of lipase activity in the starchy endosperm of germinating wheat grains

Induced triglyceride metabolism in germinating wheat grains

Induced triglyceride metabolism in germinating wheat grains

Mineral translocation in germinating wheat grain

Mineral translocation in germinating wheat grain

The pattern and control of isoprenoid quinone and tocopherol metabolism in the germinating grain of wheat (Triticum vulgare).

1. The syntheses of ubiquinone-9 and plastoquinone-9 were used as parameters respectively of mitochondrial and proplastid development in the germinating wheat grain. 2. The changes in the amounts of the tocopherols were also studied and the possible biological significance of these changes is discussed. During germination, the dimethyl tocopherols of the resting grain are probably not utilized for the synthesis of alpha-tocopherol. 3. It was demonstrated that ubiquinone synthesis, and hence probably mitochondrial development, in the aleurone cells during germination, is independent of control by gibberellic acid from the embryo. 4. The influence of light on the syntheses of the isoprenoid quinones in the etiolated wheat shoot was investigated. In particular, illumination did not stimulate the synthesis of either alpha-tocopherol or alpha-tocopherolquinone.

THE STABILITY OF WHEAT EMBRYO GLUTAMATE DECARBOXYLASE UNDER CONDITIONS OF WATER STRESS

The effect of various treatments on the stability of glutamate decarboxylase in wheat seedlings and wheat embryos was investigated in an effort to obtain information suggesting a molecular basis for desiccation resistance in plants. The decarboxylase activities of germinating wheat grains before and after desiccation were measured. Attempts were made to relate activity of the enzyme to a soluble or particulate cell fraction by differential centrifugation. The responses to desiccation by active protein preparations following defatting treatments with n-butanol were measured. The decarboxylase activity of germinating wheat increased for 54 h and the stability of the enzyme decreased during this time. Particulate cell fractions were devoid of activity. The responses of the extracted enzyme to desiccation suggest that its stability may reside in a capacity for dissociation into smaller protein components, under conditions of water stress, and that this capacity may depend upon the presence of lipids.

Supernumerary shoots in the germinating grain of bread wheat

Abstract Germinating wheat grains with up to five shoots were found in hybrid lines derived from the variety Gabo. It is possible that they were induced by weed spray hormones.

Chemical investigation of wheat

The extent and the mechanism of phytic acid decomposition in germinating wheat grain of a low-yielding and a high-yielding wheat variety have been investigated. While in the high-yielding variety this decomposition was most important on the first, fifth, and seventh day of germination, in the low-yielding variety extensive decomposition began only on the second day and reached its maximum value on the fifth day of germination. If one accepts the criterion of Mellanby for the rate of phytic acid decomposition, it appears that phytic acid is completely decomposed within seven days in the high-yielding variety and within six days in the low-yielding variety. The increase of free orthophosphate was not equivalent to the decrease of phytic acid, the difference representing the amount of orthophosphate phosphorus uptake in oxidative and photosynthetic phosphorylation. It was found that enzymatic hydrolysis of phytic acid in germinating wheat grain occurred stepwise, by the successive liberation of phosphoric acid and through the intermediate formation of penta-, tetra-, tri-, di-, and monophosphates of inositol, the final products being inositol and phosphoric acid. In ripe wheat grain before germination, only inositol hexaphosphate (phytic acid) was present.