Biomedical subjects

D B Egli

Publications and source records attributed to D B Egli.

5 recordsLinked to original sources

PubMed1987

Changes in k, rb, and na transport to shoots after anoxia.

The effect of anoxia on subsequent uptake and transport of K, Rb, and Na was examined with seedlings of barley (Hordeum vulgare L.), corn (Zea mays L.), and tall fescue (Lolium x Festuca hybrid derivative) to further our understanding of xylem loading. Roots were incubated in solutions depleted of O(2) by flushing with N(2) gas. After 1 hour exposure, plants were returned to aerated solutions for 16 hours prior to measuring uptake and transport. For each species, anoxia pretreatment significantly enhanced Na transport to the shoot. The rate of Na accumulation into roots, however, was not affected. There was no enhancement of either K or Rb accumulation in shoots, indicating specificity for Na transport. A minimum exposure to anoxia of 30 minutes and a minimum of 12 hours elapsed time was necessary to achieve the maximum rate of Na transport to the shoot in barley seedlings. Accumulation of Na in the shoot of both the control and anoxia pretreated barley plants was inhibited by anoxia and by addition of the proline analog, l-azetidine-2-carboxylic acid, during the uptake period. Enhancement of Na transport was associated with a proportional increase in the rate of synthesis of a membrane bound protein with a molecular weight of 78,000 daltons.

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PubMed1987

Sink removal and leaf senescence in soybean : cultivar effects.

Three cultivars of soybean (Glycine max [L.] Merr. cvs Harper, McCall, and Maple Amber) were grown in the field and kept continuously deflowered throughout the normal seedfill period. For all cultivars, deflowering led to delayed leaf abscission and a slower rate of chlorophyll loss. Compared to control plants, photosynthesis and ribulose 1,5-bis-phosphate carboxylase/oxygenase (Rubisco) level declined slightly faster for deflowered Harper, but for both McCall and Maple Amber, leaves of deflowered plants maintained approximately 20% of maximum photosynthesis and Rubisco level 1 month after control plants had senesced. Deflowering led to decreased leaf N remobilization and increased starch accumulation for all cultivars, but cultivars differed in that for McCall and Maple Amber, N and starch concentrations slowly but steadily declined over time whereas for Harper, N and starch concentrations remained essentially constant over time. SDS-PAGE of leaf proteins indicated that for all cultivars, deflowering led to accumulation of four polypeptides (80, 54, 29, and 27 kilodaltons). Western analysis using antisera prepared against the 29 and 27 kilodalton polypeptides verified that these polypeptides were the glycoproteins previously reported to accumulate in vacuoles of paraveinal mesophyll cells of depodded soybean plants. The results indicated that depending on the cultivar, sink removal can lead to either slightly faster or markedly slower loss of photosynthesis and Rubisco. This difference, however, was not associated with the ability to synthesize leaf storage proteins. For any particular cultivar, declines in chlorophyll, photosynthesis, and Rubisco were initiated at approximately the same time for control and deflowered plants. Thus, even though cultivars differed in rate of decay of photosynthetic rate and Rubisco level in response to sink removal, the initiation of leaf senescence was not influenced by presence or absence of developing fruits.

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PubMed1984

Polyamine Titer in the Embryonic Axis and Cotyledons of Glycine max (L.) during Seed Growth and Maturation.

Active polyamine metabolism occurs in Glycine max (L.) seeds during development. Most (>/=97%) of putrescine (Put), spermidine (Spd), spermine (Spm), and cadaverine (Cad) are present as free forms in the growing embryo. In the cotyledon or embryonic axis, Put decreases to a nearly undetectable level, while Spd level sharply increases as seed dry weight accumulation progresses. Spm level in the axis also increases along with the Spd level. There is little change in Spm level in the cotyledons. Maturation and dehydration results in a slight reduction of Spd level in the cotyledons. Cad is present in relatively large quantities (5.5-12 micromoles per gram dry weight) in the axes of mature soybean seeds. Only traces of Cad, as expressed on a dry weight basis, are found in the developing or mature cotyledons. The synthesis and accumulation of Cad in the axis begins at the time when the axis or the seed accumulates 30 to 50% of its maximum dry weight. The Cad accumulation (0.8 nanomole per axis per day) proceeds until the later stages of dehydration. When soybean plants are subjected to complete defoliation and shade during the midpoint of seed maturation, Cad accumulation in the axis and seed dry weight accumulation ceased almost immediately. The treatment, however, does not affect the viability of soybean seeds.

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PubMed1979

Rapid Changes in Translocation Patterns in Soybeans following Source-Sink Alterations.

The effects of source-sink alterations on the translocation patterns to soybean ("Fiskeby V") pods were studied using a pod leakage technique. The distribution of assimilates from a source leaf using double pulse experiments was followed at the pods at the source node and the node immediately below. Alterations were made by shading, illuminating, or excising two-thirds of the leaf area of the leaf at the node below. In control experiments both pulses exhibited identical time-course patterns at both nodes. Shading the lower leaf during the first half of the experiment and illuminating during the second reduced the distribution of (14)C-assimilate to the lower node's pods from the source leaf by approximately 30 to 50% while having no effect at the source node. Illuminating the lower leaf during the first half of the experiment followed by excision of two-thirds of that leaf's area and shading increased the import from the source leaf by 4- to 33-fold relative to the control while reducing the distribution to the source node by up to 40%. The change in distribution pattern took place in less than 30 minutes with no apparent change in the source leaf net photosynthesis or in the rate of movement to the pods. The results indicate that any alterations in the source-sink balance will quickly produce a change in the distribution patterns to the pods.

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PubMed1978

A Pod Leakage Technique for Phloem Translocation Studies in Soybean (Glycine max [L.] Merr.).

Radioactive photosynthetic assimilates, translocated to a soybean (Glycine max [L.] Merr. ;Fiskeby V') pod can be measured directly by excising the stylar tip of the pod under 20 mm ethylenediaminetetraacetate solution (pH 7.0) and allowing the material to leak into the solution. Pods at the source node received approximately 50% of the (14)C exported from the source leaf to the pod and leaked approximately 1 to 3% of this into the solution. More than 90% of the (14)C that leaked from the pods was found in the neutral fraction and, of this, about 93% was in sucrose. Fifteen amino acids were identified in the leakage including: alanine, arginine, asparagine, gamma-aminobutyric acid, glutamine, glycine, histidine, isoleucine, leucine, lysine, phenylalanine, serine, threonine, tyrosine, and valine. The majority of the (14)C in the basic fraction was found in serine ( approximately 30%) and asparagine ( approximately 23%). The inorganic ions K, Ca, P, Mg, Zn, and Fe were found in the leakage component. Nitrate was not detectable in the collected leakage solution. The absence of NO(3) (-) and the large proportion of the label in sucrose suggest a possible phloem origin for most of the material. The technique provides an uncomplicated, reproducible means of analyzing the material translocated into and through the soybean pod, as well as following the time course of label arrival at the pod.

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