Partitioning and Metabolism of Photorespiratory Intermediates

Grodzinski, Bernard; Madore, Monica A.; Shingles, R. A.; Woodrow, Lorna

doi:10.1007/978-94-017-0516-5_137

Cited by 5 publications

(3 citation statements)

References 31 publications

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“…The labeling of the stachyose pool noted during the feed period (Fig. 2F) was consistent with the view that stachyose was found mainly in the phloem stream in Salvia (Madore and Grodzinski, 1984;Grodzinski et al, 1987).…”

Section: Discussionsupporting

confidence: 88%

“…7F). In earlier studies with mesophyll cells isolated from Salvia, we did not detect labeling of stachyose from I4CO,, but we were able to detect label in both SUC and raffinose (Grodzinski et al, 1987). More recently, Beebe and Turgeon (1992) showed that the intermediary cells in Cucurbita pepo leaves were sites of synthesis of the raffinose sugars.…”

Section: Discussioncontrasting

confidence: 48%

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The Effect of Leaf Temperature and Photorespiratory Conditions on Export of Sugars during Steady-State Photosynthesis in Salvia splendens

Jiao

Grodzinski

1996

Plant Physiology

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Export and photosynthesis i n leaves of Salvia splendens were measured concurrently during steady-state 14C0, labeling conditions. Under ambient CO, and O, conditions, photosynthesis and export rates were similar at 15 and 25"C, but both declined as leaf temperature was raised from 25 to 40°C. Suppressing photorespiration between 15 and 40°C by manipulating CO, and O, levels resulted in higher rates of leaf photosynthesis, total sugar synthesis, and export. There was a linear relationship between the rate of photosynthesis and the rate of export between 15 and 35°C. At these temperatures, 60 to 80% of the carbon fixed was readily exported with sucrose, raffinose, and stachyose, which together constituted over 90% of phloem mobile assimilates. Above 35"C, however, export during photosynthesis was inhibited both in photorespiratory conditions, which inhibited photosynthesis, and in nonphotorespiratory conditions, which did not inhibit photosynthesis. Sucrose and raffinose but not stachyose accumulated i n the leaf at 40°C. When leaves were preincubated at 40°C and then cooled to 3 5 T , export recovered more slowly than photosynthesis. These data are consistent with the view that impairment of export processes, rather than photosynthetic processes associated with light trapping, carbon reduction, and sucrose synthesis, accounted for the marked reduction i n export between 35 and 40°C. Taken together, the data indicated that temperature changes between 15 and 40°C had two effects on photosynthesis and concurrent export. At all temperatures, suppressing photorespiration increased both photosynthesis and export, but above 35"C, export processes were more directly inhibited independent of changes i n photorespiration and photosynthesis.

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Section: Discussionsupporting

confidence: 88%

Section: Discussioncontrasting

confidence: 48%

The Effect of Leaf Temperature and Photorespiratory Conditions on Export of Sugars during Steady-State Photosynthesis in Salvia splendens

Jiao

Grodzinski

1996

Plant Physiology

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“…After a 15-min 14C02 feeding to an entire shoot of a nodulated alfalfa plant, Ta et al (1987) note that these amino acids were also the major labelled constituents in the basic fraction of the shoot tissues, but in the absence of a chase period, proportionally more Ser was labelled than shown in Table 3. Although changes in the specific radioactivities of Gly and Ser may reflect a change in photorespiratory C and N turnover and (or) export from leaves of nodulated and NO?-treated alfalfa plants (Grodzinski et al 1987), clearly more studies are required. Although changes in the specific radioactivities of Gly and Ser may reflect a change in photorespiratory C and N turnover and (or) export from leaves of nodulated and NO?-treated alfalfa plants (Grodzinski et al 1987), clearly more studies are required.…”

Section: Amino Acidsmentioning

confidence: 99%

Carbon partitioning in nodulated alfalfa in the presence of nitrate

Côté¹,

Bordeleau²,

Lapointe³

et al. 1989

Can. J. Bot.

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C 6~6 , R., BORDELEAU, L. M., LAPOINTE, J., and GRODZINSKI, B. 1989. Carbon partitioning in nodulated alfalfa in the presence of nitrate. Can. J. Bot. 67: 1998Bot. 67: -2004. Photosynthetic carbon partitioning from a fully expanded upper canopy leaf of nodulated alfalfa was examined in plants in which nitrogenase activity and leghemoglobin content were reduced by 70 and 50%, respectively, in the presence of 10 mM KNO,. The nitrite level in nodules of nitrate-treated plants was 12.5 + 0.5 pg Nlg FW and 0.3 f 0.4 pg Nlg FW in the control plants. Growth of axillary shoots and roots was markedly enhanced in treated plants, as were steady state leaf photosynthesis (54 f 4 to 113 f 8 pmol CO,/(mg chlorophyll. h)) and translocation speed (0.37 f 0.05 to 0.56 + 0.05 cm . min-I). Nodules received 5 % of the newly fixed carbon of the feed leaf 7 days after transfer to NO;, compared with less than 1 % for the control plants maintained on NO;-free medium. Sucrose was the major 14C-labelled photoassimilate, although small amounts of labelled raffinose-series sugars were detected in leaves of treated plants. The specific activity of asparagine in the leaf increased dramatically, consistent with a reduction in both nitrogen fixation and the import of unlabelled asparagine from nodules. Concentrations of alanine, y-amino butyric acid, glutamic acid, and aspartic acid were greater in all tissues of treated plants. However, pools of asparagine, glutamine, serine, glycine, threonine, and arginine were lower in leaf, shoot, and root tissue of the treated plants. The levels of all amides and amino acids in the nodules remained high in treated plants. The high levels of nitrite and amino acids in nodules of treated plants were correlated with reduced leghemoglobin content and nitrogenase activity, but this does not explain directly the mechanism of suppression of nitrogen fixation in alfalfa exposed to nitrate. Nevertheless, the ability of alfalfa nodules, which have an indeterminate growth pattern, to compete for carbon from upper leaves in the canopy may explain their longevity under NO; stress in the field.Key words: partitioning, photosynthesis, 14C0,, alfalfa, nitrate, nitrogenase, amino acids. C~T E , R., BORDELEAU, L. M., LAPOINTE, J., et GRODZINSKI, B. 1989. Carbon partitioning in nodulated alfalfa in the presence of nitrate. Can. J. Bot. 67 : 1998-2004.La rtpartition des composCs carbonks photosynthttisCs 2 partir d'une feuille mature de la partie suptrieure de la tige principale a Ctt CtudiCe chez la luzerne nodulte. L'activitt nitrogtnasique et la concentration en leghtmoglobine diminuent de 70 et 50%, respectivement, suite i une application de 10 mM KNO, pendant 7 jours. La concentration en nitrite dans les nodules des plants traitts est de 12,5 f 0,5 pg Nlg mf et de moins de 0,3 f 0,4 pg Nlg mf chez les plantes contrales. Chez les plants trait&, on observe une stimulation de la croissance des tiges axillaires et des racines de mCme qu'une augmentation du taux de photosynthkse 2 1'Cquilibre (54 + 4 2 113 + 8 pmol CO,/(mg ...

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