Der Einfluß des Bors auf verschiedenaltrige Populationen von Wolffia arrhiza (L.) Wimm, in Chemostat en-Kultur

Eichhorn, M.; Augsten, H.

doi:10.1016/s0015-3796(17)30977-0

Cited by 12 publications

(4 citation statements)

References 25 publications

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“…An aquatic higher plant, Wolfjfa arrhiza, also has a higher photosynthetic rate and accumulates larger amounts of carbohydrates per dry weight when grown in lowered boron concentrations (2). In the diatom, changes in photosynthesis are a secondary response to boron deficiency because these organisms still show a growth requirement for boron when cultured in the dark under heterotrophic conditions (5).…”

Section: Discussionmentioning

confidence: 99%

Effects of Boron Deficiency on ⁸⁶Rubidium Uptake and Photosynthesis in the Diatom Cylindrotheca fusiformis

Smyth¹,

Dugger²

1980

Plant Physiol.

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Section: Discussionmentioning

confidence: 99%

Effects of Boron Deficiency on ⁸⁶Rubidium Uptake and Photosynthesis in the Diatom Cylindrotheca fusiformis

Smyth¹,

Dugger²

1980

Plant Physiol.

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“…One symptom of boron deficiency in higher plants and algae is increased OPP activity (5). Plants grown under Bdeficient conditions show increased activity of G6PDH, the first enzyme in the OPP (19).…”

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confidence: 99%

Effect of Boron Deficiency on Photosynthesis and Reductant Sources and Their Relationship with Nitrogenase Activity in Anabaena PCC 7119

García-González¹,

Mateo²,

Bonilla³

1990

Plant Physiol.

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Nitrogenase activity of Anabaena PCC 7119 is inhibited under conditions of boron deficiency. To elucidate the mechanisms of this inhibition, this study examined how the deficiency of boron affected photosynthesis, photosynthetic pigments, the enzymes of the oxidative pentose phosphate pathway, and respiration of Anabaena PCC 7119 cultures. After 24 to 48 hours of boron deficiency, reductions in photosynthetic O2 evolution and in CO2 fixation were observed. At the same time, the activities of oxidative pentose phosphate pathway enzymes and respiration increased significantly with boron deficiency. No change was observed in these processes when assays were performed after 4 to 6 hours of deficiency, a time at which nitrogenase activity was severely inhibited. These results suggest that the requirement for boron in N2 fixation is independent of its effects on photosynthesis and reductant supply.piration. In addition, the newly formed NADPH in cyanobacteria can be used for ATP formation in the dark (22).One symptom of boron deficiency in higher plants and algae is increased OPP activity (5). Plants grown under Bdeficient conditions show increased activity of G6PDH, the first enzyme in the OPP (19). In N2-fixing heterocystous cyanobacteria, the activities of the OPP enzymes, G6PDH and 6PGDH, are 15 times higher in the heterocysts than in the vegetative cells (24). The high activities of these enzymes in heterocysts, in light or dark, suggest that the OPP is the major NADPH source for the transfer or electrons to nitrogenase (15). In heterocysts, NADPH can supply electrons to nitrogenase in light and dark, whereas NADH acts as an electron donor in a strictly light-dependent reaction via PSI (8).The goal of this study was to determine whether photosynthesis or the OPP is directly involved in the inhibition of N2 fixation by boron removal.A need for boron is not a general feature in cyanobacteria and may be restricted to N2-fixing strains (14). The physiological mechanism of this requirement has not been elucidated, but evidence of boron involvement both in nitrogenase activity and as protection against 02 diffusion has been shown (9). In the present study, we have investigated its relation with photosynthesis and the Opp.2Nitrogen fixation requires a large input of reducing power and ATP. In cyanobacteria, energy to form reductant is derived from photosynthesis, but the concomitant O2 release by PSII may also interfere with 02-sensitive nitrogenase. Therefore, in heterocystous strains like Anabaena PCC 7119, the major electron sources for the reduction of N2 are sugars that are formed photosynthetically in the vegetative cells before transfer into the heterocysts (25).In cyanobacteria, sugar breakdown only occurs via the OPP, which consists primarily of the same enzymes that operate in the Calvin cycle, supplemented with two NADP+-specific dehydrogenases: G6PDH and 6PGDH (22). It is clear that there is a close relationship between photosynthesis and res-

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“…The interaction of borate with 6-phosphogluconate dehydrogenase has been suggested as a mechanism for controlling the flow of intermediates into phenolic compounds (Lee and Aronoff 1967). With sunflower, increased activities of 6-phosphogluconate dehydrogenase and the pentose phosphate pathway (measured by inhibitors) are associated with boron-deficient conditions and the associated accumulation of phenols (Eichhorn and Augsten 1974, Lee and Aronoff 1967, Timashov 1970. In contrast, C. fusiformis does not increase the relative activity of the pentose phosphate pathway during the early periods of boron-deficient culture.…”

Section: Discussionmentioning

confidence: 99%

“…Other studies with metabolic inhibitors for an extended period of time (Lewin and Chen 1976 . (Eichhorn andAugsten 1974. T.mashov 1970) also in-In our studies "^^'^ ^•J""f''''^''' P"'^^'^'^'"^'''d icate that activit/of the pentose pho^pHate^^^^^^^^^^^^ sociate wit growt^h în boron-^deficient medmm^^r:^ U and Dugger 1980).…”

Section: Introductionmentioning

confidence: 99%

Cellular changes during boron‐deficient culture of the diatom Cylindrotheca fusiformis

Smyth

Dugger

1981

Physiologia Plantarum

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The effects of boron‐deficient culture were studied on the unicellular diatom. Cylindrotheca fusiformis Reimann and Lewin. After 24 to 30 h, cell division was almost completely inhibited in boron‐deficient cultures. By 48 h of culture, boron‐deficient diatoms had approximately twice the modal cell volume of control cells, and at least twice the amount of organic constituents such as protein (2.0x), insoluble carbohydrate (2.4x), total phenols (2.6x), and chlorophyll at (2.1x). Boron deficiency led to irreversible damage after this time. Dark respiration was 1 nmol O2/min × 106 cells for both control and boron‐deficient diatoms prior to 40 h of culture. By 48 h, the respiratory rate of boron‐deficient diatoms was double that of controls. The proportion of 14C‐glucose metabolized by the pentose phosphate pathway was similar in both control and boron‐deficient diatoms after 24 and 48 h of culture. After 24 h, the in vitro activity of glucose‐6‐phosphate dehydrogenase was similar in both control and boron‐deficient cells, although the pool size of its substrate, glucose‐6‐phosphate, was 26% greater in boron‐deficient cells. The cellular amount of glucose‐6‐phosphate dehydrogenase continued to increase once mitosis was arrested in boron‐deficient diatoms. Boric acid (1 mM) inhibited 6‐phosphogluconate dehydrogenase by 18% in diatom homogenates. During the early stages of boron deficiency, the uptake of silicate, nitrate, and phosphate, and the in vitro activity of β‐glucosidase were similar to control diatoms. After cell division was inhibited, boron‐deficient diatoms accumulated more nitrate and phosphate, and retained a higher level of β‐glucosidase than control cells.

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Der Einfluß des Bors auf verschiedenaltrige Populationen von Wolffia arrhiza (L.) Wimm, in Chemostat en-Kultur

Cited by 12 publications

References 25 publications

Effects of Boron Deficiency on ⁸⁶Rubidium Uptake and Photosynthesis in the Diatom Cylindrotheca fusiformis

Effects of Boron Deficiency on ⁸⁶Rubidium Uptake and Photosynthesis in the Diatom Cylindrotheca fusiformis

Effect of Boron Deficiency on Photosynthesis and Reductant Sources and Their Relationship with Nitrogenase Activity in Anabaena PCC 7119

Cellular changes during boron‐deficient culture of the diatom Cylindrotheca fusiformis

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Der Einfluß des Bors auf verschiedenaltrige Populationen von Wolffia arrhiza (L.) Wimm, in Chemostat en-Kultur

Cited by 12 publications

References 25 publications

Effects of Boron Deficiency on 86Rubidium Uptake and Photosynthesis in the Diatom Cylindrotheca fusiformis

Effects of Boron Deficiency on 86Rubidium Uptake and Photosynthesis in the Diatom Cylindrotheca fusiformis

Effect of Boron Deficiency on Photosynthesis and Reductant Sources and Their Relationship with Nitrogenase Activity in Anabaena PCC 7119

Cellular changes during boron‐deficient culture of the diatom Cylindrotheca fusiformis

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Effects of Boron Deficiency on ⁸⁶Rubidium Uptake and Photosynthesis in the Diatom Cylindrotheca fusiformis

Effects of Boron Deficiency on ⁸⁶Rubidium Uptake and Photosynthesis in the Diatom Cylindrotheca fusiformis