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R L Bieleski

Publications and source records attributed to R L Bieleski.

16 recordsLinked to original sources
PubMed1992

Physiological changes accompanying senescence in the ephemeral daylily flower.

The daylily flower, Hemerocallis hybrid cv Cradle Song, develops from the opening bud to full senescence in 36 hours. Unlike other ephemeral flowers studied to date, it does not respond to ethylene, but other senescence phenomena are similar. There was a small respiration climacteric coinciding with early flower senescence, and it was also observed in isolated petals and petal slices. Cycloheximide abolished the climacteric and delayed senescence in all three systems. Petal apparent free space increased from 30% at bud opening to 38% at the onset of senescence, and sugar efflux increased from 0.2 to 2.8 milligrams per gram of fresh weight per hour during the same period. A sharp increase in ion efflux from 0.8 to 4.0 micromoles of NaCl equivalents per gram of fresh weight per hour, coinciding with the climacteric, was abolished by cycloheximide. Uptake of radiolabeled inorganic phosphate by petal slices from 100 micromolar solution increased during onset of senescence from 6 to 10 nmoles per gram of fresh weight per hour. Half was esterified; of this, 14% went into ATP, and the cellular energy charge remained high at 0.86 during senescence. The proportion incorporated into phospholipid (2.2%) did not change during senescence, but the proportion in phosphatidyl choline increased and in phosphatidyl glycerol decreased during senescence. The general phosphate ester pattern in presenescent slices closely resembled that in other plant tissues except that phospholipid precursors were more prominent (approximately 20% of total organic (32)P versus 5%). In senescent slices, the proportion of hexose phosphates decreased from 40 to 15% of total organic (32)P and that of phospholipid precursors increased to approximately 50%, suggesting that phospholipid synthesis was blocked early in senescence.

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PubMed1992

Mannitol Synthesis in Higher Plants : Evidence for the Role and Characterization of a NADPH-Dependent Mannose 6-Phosphate Reductase.

Mannitol is a major photosynthetic product in many algae and higher plants. Photosynthetic pulse and pulse-chase (14)C-radiolabeling studies with the mannitol-synthesizing species, celery (Apium graveolens L.) and privet (Ligustrum vulgare L.), showed that mannose 6-phosphate (M6P) and mannitol 1-phosphate were among the early photosynthetic products. A NADPH-dependent M6P reductase was detected in these species (representing two different higher plant families), and the enzyme was purified to apparent homogeneity (68-fold with a 22% yield) and characterized from celery leaf extracts. The celery enzyme had a monomeric molecular mass, estimated from mobilities on sodium dodecyl sulfate-polyacrylamide gels, of 35 kilodaltons. The isoelectric point was pH 4.9; the apparent K(m) (M6P) was 15.8 millimolar, but the apparent K(m) (mannitol 1-phosphate) averaged threefold higher; pH optima were 7.5 with M6P/NADPH and 8.5 with mannitol 1-phosphate/NADP as substrates. Substrate and cofactor requirements were quite specific. NADH did not substitute for NADPH, and there was no detectable activity with fructose 6-phosphate, glucose 6-phosphate, fructose 1-phosphate, mannose 1-phosphate, mannose, or mannitol. NAD only partially substituted for NADP. Mg(2+), Ca(2+), Zn(2+), and fructose-2,6-bisphosphate had no apparent effects on the purified enzyme's activity. In vivo radiolabeling results and the enzyme's kinetics, specificity, and distribution (in two-plant families) all suggest that NADPH-dependent M6P reductase plays an important role in mannitol biosynthesis in higher plants.

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PubMed1977

Involvement of phaseolotoxin in halo blight of beans: transport and conversion to functional toxin.

Phaseolotoxin ([N(delta)-phosphosulfamyl]ornithylalanylhomoarginine) is produced by Pseudomonas phaseolicola (Burkh.) Dows. in liquid culture. When phaseolotoxin was applied to leaves of bean (Phaseolus vulgaris L.) at 0.1 to 1 nmoles/g fresh weight of leaf by a prick-assay procedure, the characteristic "halo" symptom of bean halo blight disease developed after 24 to 48 hours. At higher concentrations (10-100 nmoles/g fresh weight) the systemic symptoms, which are commonly a feature of diseased plants, also developed after 24 to 48 hours.When applied to bean leaves, phaseolotoxin was rapidly broken down by the sequential removal of homoarginine and alanine. N(delta)-Phosphosulfamylornithine was the major product formed, although phosphosulfamate and unreacted phaseolotoxin were also present. When P. phaseolicola infected bean plants, very little phaseolotoxin was detected within the plant, but the amount of N(delta)-phosphosulfamylornithine formed was sufficient to account for the observed chlorosis, the ornithine accumulation, and the systemic symptoms. N(delta)-Phosphosulfamylornithine therefore seemed to be the main functional phytotoxin of bean halo blight disease.When (35)S-phaseolotoxin was applied to primary leaves, (35)S (assumed to be a mixture of phaseolotoxin, N(delta)-phosphosulfamylornithine, and phosphosulfamate) was actively loaded into the fine veins of the leaf and moved through the plant in the vascular system at a speed greater than 3 cm/hour, particularly toward the apical and lateral buds and the root tips. Certain factors which affect pholem transport (arsenate, cold) affected toxin movement and the expression of systemic symptoms. Autoradiography suggested that the (35)S was transported in the phloem.A model for the involvement of phaseolotoxin in halo blight disease is presented.

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PubMed1972

Turnover of Phospholipids in Normal and Phosphorus-deficient Spirodela.

When (32)P(1) was supplied as a 15-minute pulse to normal Spirodela oligorrhiza plants, the first phospholipid to become fully labeled was phosphatidic acid. Phosphatidyl glycerol reached maximum labeling before the other major phospholipids. In phosphorus-deficient plants, however, phosphatidyl glycerol became labeled much more slowly than either phosphatidyl choline or phosphatidyl ethanolamine, and also the proportion of phosphatidyl glycerol present was smaller. Thus, phosphatidyl glycerol synthesis is sensitive to phosphorus deficiency. Since most of the phosphatidyl glycerol present in Spirodela was localized in the chloroplast, this effect appeared to be specifically one on chloroplast composition. The phosphorus-deficient chloroplast had a 60% lower phospholipid content and a normal phospholipid pattern, but the phospholipid which was present was apparently cycling much less rapidly. Zeatin, which ameliorates the visual symptoms of phosphorus deficiency, also reduces the effect of phosphorus deficiency on phospholipid synthesis.

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PubMed1970

Response of Spirodela oligorrhiza to Phosphorus Deficiency.

The duckweed Spirodela oligorrhiza, growing in sterile defined nutrient media, was used to study some responses of plants to phosphorus deficiency. On a phosphate-deficient medium, growth of Spirodela soon slowed and eventually ceased. Older leaves became chlorotic, but newly formed leaves were dark green and contained much anthocyanin. The photosynthesis rate fell gradually, roots elongated, and chloroplasts became filled with starch.NITROGEN METABOLISM WAS NOT MARKEDLY AFFECTED: the total protein content changed only slightly, and, although levels of glutamine and asparagine increased, the concentrations of the other amino acids remained constant. The effects of phosphorus deficiency on Spirodela are discussed in relation to those found in other higher plants.

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PubMed1969

Phosphorus compounds in translocating Phloem.

Phosphate-(32)P was introduced into a turnip leaf, and 3 hr later, the vascular bundles were stripped from the petiole and their phosphate ester pattern was studied. The pattern did not alter along their length and was like that of other tissues. Pumpkin leaves were painted with phosphate-(32)P; and later, the petioles were cut, the sieve tube exudates were collected and their phosphate ester patterns were studied. Exudates collected after 10 min had a high proportion of their (32)P present in P(i) and nucleoside triphosphates, while exudates collected after long translocation times (4-22 hr) had a lower proportion in these, and a higher proportion in hexose monophosphates and UDP glucose. In general, the ester patterns were like those of other tissues. The results indicate that sieve tubes are metabolically active, and that P(i) is the primary form in which phosphorus moves in the phloem.

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PubMed1968

Levels of phosphate esters in spirodela.

The duckweed Spirodela oligorrhiza was grown in sterile nutrient solutions that contained 1 mm phosphate-(32)P at various specific activities. In solutions with activities higher than 2 muc per mumole per ml, plant growth was inhibited after a time, and the physical appearance of the plants was affected. The critical level of radiation, at which growth was first affected, corresponded to 5 kilorads.Plants were grown for 9 days (5 generations) in a culture solution containing phosphate at 0.5 muc per mumole per ml (radiation load approx 0.5 kilorads) so that all phosphorus-containing materials in the tissue became uniformly labeled. The various radioactive compounds were extracted, chromatographed, identified, and their radioactivity was measured. From this radioactivity plus the specific activity of the supplied phosphate, the amount of each compound was calculated. The data constitute a complete balance-sheet for phosphorus in a plant tissue. The identity of 98% of the phosphorus in the tissue was determined. Inorganic phosphate (32,700 mmumoles/g fr wt) was the predominant phosphorus-containing compound; RNA (5100 mmumoles P/g fr wt) was the main organic phosphate; phosphatidyl choline (1600 mmumoles/g fr wt) was the main phospholipid, and glucose-6-phosphate (500 mmumoles/g fr wt) the main acid-soluble phosphate ester. Amounts of other phosphorus compounds are given.

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PubMed1968

Effect of phosphorus deficiency on levels of phosphorus compounds in spirodela.

When Spirodela plants are transferred to a phosphate-deficient medium, growth slows down immediately, and ceases after 14 days. During this time, inorganic phosphate content falls from 30 to 0.7 mumoles/g fresh weight of tissue, phosphate ester content from 3.5 to 0.6 mumoles/g, phospholipid content from 3.5 to 1.2 mumoles/g, and residual phosphate (mainly RNA) content from 7.5 to 2.0 mumoles/g. Relative proportions of the various phosphate esters, and relative proportions of the various phospholipids, are not markedly affected by phosphate deficiency. Turnover rates of phosphate esters are somewhat higher in phosphate-deficient tissue. In control tissue, inorganic phosphate is present in 2 pools; a metabolic (12%) and a non-metabolic pool (88%). In phosphate-deficient tissues, most of the inorganic phosphate (>90%) is in the metabolic pool. Non-metabolic phosphate is presumably stored in the vacuole, and is not readily accessible to the tissue, so that growth normally occurs at the expense of external phosphate. During deficiency, growth is limited by the rate at which phosphate can be transported through the tonoplast and tissue to the growing point. Growth ceases when the supply of non-metabolic phosphate is exhausted. Metabolic phosphate is presumably located in the cytoplasm: it can not be used for growth. Nor can the plant respond to deficiency by making some phosphorus compounds at the expense of others. In this respect, phosphorus deficiency and nitrogen deficiency are dissimilar.

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PubMed1966

Accumulation of phosphate, sulfate and sucrose by excised Phloem tissues.

Excised petiolar vascular bundles and excised phloem tissues have been shown to take up phosphate, sulfate and sucrose by a true accumulation process and against high concentration ratios. Phosphate was accumulated principally as inorganic phosphate, and sucrose principally as sucrose. The rates of accumulation of the 3 solutes into the phloem-containing tissues were from 4 to 35 times higher than into comparable parenchyma tissue. It is suggested that this active accumulation mechanism plays an important role in the phenomenon of phloem transport.THE EXCISED VASCULAR, PHLOEM AND PARENCHYMA TISSUES SHOW AN AGING PHENOMENON: aerating the excised tissues for 18 hours prior to their use causes marked changes in the accumulatory behavior of the tissue. The data suggest that 1 phosphate accumulation system of low affinity but high capacity exists in fresh tissue, and that aging allows the development of a second, additional phosphate accumulation mechanism of high affinity and low capacity. A possible role in the control of phosphate movement is suggested.

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PubMed1966

Sites of accumulation in excised Phloem and vascular tissues.

Excised pieces of vascular bundle and phloem tissue were allowed to accumulate radioactive phosphate and sulfate, and were then sectioned and autoradiographed so as to detect the sites of accumulation. Special methods were needed to prevent any diffusion of the radioisotope. Some autoradiographs obtained are presented. In excised celery vascular bundles, the most radioactive area and hence the most actively accumulating tissue was the young secondary phloem at the sides of the bundle. In intact plants, the same tissue was the most active in translocating. In excised apple phloem there was some variation in behavior, but again the young secondary phloem was generally the most actively accumulating tissue. Accumulation activities of individual cells in the phloem and vascular tissue were compared. It appeared that all cell types, ray, phloem and xylem parenchyma, cambial cells and sieve tubes, accumulated at least 5 times more actively than did the cortical parenchyma cells. The sieve tubes were among the most actively accumulating cells present, accumulating 20 times more actively than the cortical parenchyma cells. It is concluded that accumulation processes have a primary role to play in the mechanism of phloem transport.

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