Low Temperature Effects on Soybean (Glycine max [L.] Merr. cv. Wells) Free Amino Acid Pools during Germination

Abstract

The free amino acid concentrations in cotyledons and axes of soybean (Glycine max IL.I Merr. cv. Wells) seedlings were determined by automated single column analysis after germiation at 10 and 23 C. After 5 days germination at 10 C, glutamate and aspartate were in high concentration in both cotyledons and axes (38 and 24% of total free amino acids recovered, respectively), whereas the concentrations of their amide derivatives, asparagine and glutamine, were iow in cotyledons (4.4%) and high in axes (21%). In contrast, after 5 days germination at 23 C, asparagine and glutamine accounted for 22 and 45% of total free amino acids in cotyledons and axes respectively, and aspartate and glutamate concentrations were low. The activities of glutamine synthetase and asparagine synthetase were considerably lower in tissues from the 10 C treatment than those from the 23 C treatment.Aspartate and glutamate concentrations were nearly equal in all but one sample. Both glutamate oxaloacetate transaminase and glutamate dehydrogenase activities were much higher in axis tissues at 23 C as compared to 10 C. Arrhenius plots of axis glutamate oxaloacetate transaminase and glutamate dehydrogenase activities were biphasic and triphasic, respectively, with energies of activation for both increasing with low temperature. Energies of activation were identical for glutamate oxaloacetate transaminase from 10 and 23 C treatments but much higher for glutamate debydrogenase from 23 C-treated axes. This indicates a difference in enzyme complement for glutamate dehydrogenase with the two treatments.Hydrolysis of free amino acid sample (basic fraction) aliquots showed large quantities of peptides in 23 C-treated axes at 2 days, while few or no peptides were found in the 10 C treatment. Amino acid residues most prevalent in peptides were aspartate, threonine, serine, glutamate, and glycine.In legume germination the proportions of amino acids in storage proteins are not reflected by the proportions of free amino acids which occur during storage protein mobilization of such species as Glycine max (5,15). This is largely due to interconversions of amino acids released from storage proteins to produce both new nonprotein and protein amino acids (2).Slower soybean germination (as measured by radicle emergence from the testa) at low temperature appears to be due in part to high E.3 values at suboptimal germination temperatures for the enzymes involved in energy transduction (10). Inasmuch as amino acid interconversions are in many cases energy-requiring processes, we decided to determine the effects of low temperature on free amino acid pools in soybean seedlings. Also, because we found high levels of aspartate, glutamate, asparagine, and glutamine, we surveyed several enzymes which are considered primary in the metabolism of these amino acids (GDH, GS, AsnS, and GOT). The activities of these enzymes from soybean seedlings grown at low and optimal temperatures appear to be responsible for many of the observed differences in free amino acid pools...

Comparison of gamma-aminobutyric acid production in Thai rice grains

“…Moreover, Duke et al (1978) found high glutamic acid concentrations in both cotyledons and axes of soybean seedling after 5 days of germination at 10°C.…”

Role of the Testa in Preventing Cellular Rupture During Imbibition of Legume Seeds

“…imbibition and germination (8,9,11,21,22). This may be due to incorporation of cytosol pools of these enzymes into mitochondria during hydration, de novo synthesis, or to an increase in structural integrity of mitochondria during hydration.…”

“…All dehydrogenase and dehydrogenase-linked enzyme assays were conducted spectrophotometrically measuring the reduction of NAD(P)+ or the oxidation of NAD(P)H at 340 nm with a Pye Unicam SP8-100 double-beam spectrophotometer at 30 C. Except for the assay buffer (100 mm Hepes), assays are as previously described for GDH2 and MDH (7), NADP-ICDH and G6P-DH (8), and GOT (9). Assays for AK were coupled to G6P-DH and reaction mixtures (2 ml) contained, in order of addition and in final concentration: 75 from horse heart (Sigma), reduced with ascorbate and dialyzed with 1,000 volumes H20 for 18 h at 5 C; A5w/Aw = >20), and 50 A1 enzyme preparation to a final volume of 1.0 ml.…”

The Peptide Pools of Germinating Barley Grains: Relation to Hydrolysis and Transport of Storage Proteins

“…Although there have been a number of reports indicating that growing seedlings may contain such pools (e.g. 4,8) these may be subject to other interpretations. It seems likely that the methods employed here could be applied with little or no modification to other tissues in order to establish the general existence and possible function of peptide pools in plant tissues.…”