Regulatory Mechanisms of Reproductive Effort in Plants II. Plasticity in Reproductive Energy Allocation and Propagule Output of Glycine max Merr. (Leguminosae) Cultivated at Varying Densities and Nitrogen Levels

Abstract Plasticity in growth, reproductive energy allocation (RA), and reproductive output were studied in Glycine max Merr. Cv. Enrei (Leguminosae) grown under varying densities and soil nitrogen levels.
Marked plastic responses were detected in individual biomass, the patterns of resource allocation to total reproductive structures (RA) and also to propagules, reproductive outputs, and propagule weight under changing densities and soil nitrogen levels. Plants cultivated at higher densities exhibited proportionately lower individual biomass, lower RA, lower seed output, and smaller seed size in response to increasing density and decreasing soil nitrogen levels, although some deviations were observed, especially in the highest density plot with no fertilization. Differences due to different N-levels were not as great as those to changing density, which may in part be due to the fact that soybean has nitrogen-fixing bacteria in root tubercles, just as in any other Leguminosae. Fecundity was also maintained at the similar high rates of 80–97% in all plots examined, although slight but steady decreases were noted with increasing density. This resemblance in fecundity may be due to its strong inbreeding system.
Another important finding was that seed production under limited resource availability, notably lack of ample solar radiation due to strong interference at higher density plots, is exceedingly costly. This was most clearly exhibited by a sharp increase in relative energy partitioning to a single propagule in response to the increased density, the relative energy cost to a single propagule (RA) increasing from one to seven-fold. The results obtained in this study coincide well with the findings made in other plants, e.g., Helianthus annuus, Oryza sativa , and Coix ma-yuen , with the same experimental designs.     

Cadaverine Involved in Urate Degrading Activity (Uricase Activity) in Soybean Radicles

Cadaverine, a 5-carbon diamine, was identified as the cofactorof uricase activity previously found in soybean seedlings. Thesubstance purified from freeze dried hypocotyls was subjectedto liquid chromatography, mass spectrometry, ¹H- and ¹³C-nuclearmagnetic resonance spectrometry for identification. The concentrationsof cadaverine in 3-day-old radicles and hypocotyls were 2.37mM and 5.09 mM, respectively. Other polyamine concentrationswere low. Biogenic polyamines (cadaverine, putrescine, spermidineand spermine) functioned as cofactors, whereas conjugated polyamines(tyramine and histamine) and amino acids had no effect. Theaddition of catalase to the assay system counteracted the effectof cadaverine. Peroxide at appropriate concentrations actedlike cadaverine with an identical K_m value, suggesting thaturate degrading activity can be ascribed to the diamine oxidase-peroxidasesystem. (Received October 19, 1982; Accepted December 23, 1982)     

Stress-Induced Alterations in Metabolism of Γ-Aminobutyric Acid in Rat Brain

The effect of a stressful manipulation on the metabolism of gamma-aminobutyric acid (GABA) in the rat brain was studied. Application of an immobilized stress to animals induced a significant increase in the striatal and hypothalamic GABA contents without affecting those in other central structures examined. It was also found that the increase in striatal GABA level preceded that in the hypothalamus. This increase in steady-state levels of GABA in the striatum and hypothalamus disappeared at 12 h after the termination of the application of stress for 3 h, which exhibited a maximal stimulatory action on the GABA contents in both central areas. The activity of L-glutamic acid decarboxylase was found to be significantly elevated in the striatum and hypothalamus following the stress application with a concomitant decrease in the content of L-glutamic acid, which is converted to GABA by the catalytic action of the latter enzyme. The in vivo turnover of GABA in the brain was estimated by taking advantages of the postmortem accumulation of GABA following decapitation and of the selective inhibitory action of a low dose of aminooxyacetic acid on the GABA degrading system, respectively. Analysis using these two different methods revealed that the cerebral turnover of GABA in vivo was not significantly altered under stressful situations despite of the increase in its steady-state level. These results suggest that central GABA system may respond to the input of painful stimuli resulting from the application of a severe physical and psychological stressor, in addition to the well-known functional alterations in catecholamine neurons. The functional significance of these alterations in the central GABA neurons is also discussed.     

A novel guanine-guanine base pairing: crystal structure of a complex between 7-methylguanosine and its iodide.

7-Methylguanosine, one of the biologically important minor nucleosides, could be crystallized as a complex of its zwitterionic form and its iodide, and the crystal structure was determined by the X-ray diffraction method. The crystals belong to the triclinic space group P1 with the unit cell dimensions: a = 7.678(1), b = 18.094(3), and c = 5.711(1) A, alpha = 79.32(1), beta = 80.14(1) and gamma = 76.90(1) degrees. The structure was solved by the heavy atom method and refined by the least-squares method to give a final R index of 0.075. The novel reverse Watson-Crick type base pairing observed between a positively charged molecule and a deprotonated one indicates that the deprotonation at the N(1) position promoted by the alkylation at the N(7) position may interrupt the formation of the normal Watson-Crick type GC base pair. The conformations about the glycosidic bond and the sugar puckering are quite different between the two molecules: the former has anti and C(4')-exo,C(3')-endo and the latter syn and C(1')-exo-C(2')-endo.     

Chain conformation of copoly(γ-methyl D,L-glutamate)

Copolymers of γ-methyl D - and L -glutamates with various D /L ratios were prepared. Infrared absorption spectra of solid films were measured and sums of right- and left-handed helix contents were determined from intensities of amide V bands. Farultraviolet absorption spectra and optical rotatory dispersion of these copolymers in solutions are used to ascertain their helical character. Chain conformations of DL -copolypeptides are discussed.     

Relative Activities of NAD- and NADP-Isocitric Dehydrogenases in Bean Mitochondria Modified by Glycerol or NADP

Mitochondria from cotyledons of Vigna sesquipedalis (L.) Fruwirth (starchy seed) showed no NAD-isocitric dehydrogenase (NAD-IDH) activity by the methods which have been known to be useful for the detection of NAD-IDH in mitochondria of plants including castor bean and alaska pea. When the Vigna cotyledon mitochondria were treated with glycerol, NAD-IDH activity appeared and NADP-isocitric dehydrogenase (NADP-IDH) activity was inhibited. The inhibition of mitochondrial NADP-IDH by glycerol was overcome by the addition of excess NADP.On the other hand, NADP-IDH activity in the soluble fraction of cell components was only slightly inhibited by glycerol and no NAD-IDH activity was elicited.It was postulated that NADP-IDH in mitochondria is converted to NAD-IDH by glycerol and back to NADP-IDH with NADP by the alteration in the spatial configuration of the enzyme. However, there could be 2 proteins as the other possibility.The NADP-IDH in the soluble fraction which is not subject to such alteration is different from the mitochondrial NADP-IDH.