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1985 (1)
1977 (1)
1Author    Claus Buschmann, H. Artm, K. LichtenthalerRequires cookie*
 Title    Hill-Activity and P700 Concentration of Chloroplasts Isolated from Radish Seedlings Treated with -Indoleacetic Acid, Kinetin or Gibberellic Acid  
 Abstract    The Hill-activity (reduction of DCPIP or methylviologen) and the concentration of P700 were studied in chloroplasts isolated from cotyledons of radish seedlings (R aphanus sativu s L. Saxa Treib), which had been grown with the addition of ^-indoleacetic acid (IA A), kinetin, or gib­ berellic acid. 1) The photosynthetic activity of young chloroplasts from 3 day old R aphanus seedlings is very high (c. 180 /*mol 0 2/mol chlorophyll X h) and decreases continuously thereafter with increasing age. The steady state Hill-activity is readied after 8 to 10 days (values of 55 to 50 wmol 0 2/mg chlorophyll X h). 2) Chloroplasts from plants treated with IAA or kinetin not only exhibit higher plastoquinone levels *> 2, but also a higher P700-content and a higher Hill-activity. The promotion effect is more pronounced with kinetin (+ 36 to 40%) than with IAA (+ 1 2 to 17%). 3) Gibberellic acid has a different effect on composition and activity of chloroplasts. In younger seedlings the Hill-activity appears to be somewhat stimulated, without promotion effect on plasto­ quinone 2 or P700 concentration. After 10 days GA3-treated plants show signs of chlorosis combined with a strong decrease in photosynthetic activity. 4) The data clearly demonstrate that the composition and activity of the photosynthetic ap­ paratus are under phytohormone control. IAA and even better kinetin promote the light induced formation of pigment systems and electrontransport chains. GA3 seems to block the rebuilding of the photosynthetic apparatus under steady state conditions. 
  Reference    (Z. Naturforsch. 32c, 798 [1977]; received March 22/ July 4 1977) 
  Published    1977 
  Keywords    Hill-Activity, Indoleacetic Acid, Kinetin, Gibberellic Acid, Chloroplast Development 
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 TEI-XML for    default:Reihe_C/32/ZNC-1977-32c-0798.pdf 
 Identifier    ZNC-1977-32c-0798 
 Volume    32 
2Author    U. Margna, L. Laanest, E. Margna, T. VainjärvRequires cookie*
 Title    L-Tyrosine as a Precursor of Flavonoids in Buckwheat Cotyledons  
 Abstract    Exogenous L-tyrosine was incorporated 1 3 -1 4 tim es less effectively than exogenous L-phenyl-alanine into flavonoids in excised cotyledons o f 3 days old buckw heat seedlings but proved to be an only 5 times poorer precursor when the experim ents were carried out with 5 days old material. Simultaneous administration o f L-phenylalanine m arkedly reduced incorporation o f L-tyrosine into flavonoids. A similar decrease in the utilization o f exogenous L-tyrosine for flavonoid b io­ synthesis occurred in kinetin-treated cotyledons. H owever, in cotyledons treated with high doses o f glyphosate, an inhibitor o f the shikim ic acid pathway, an increase in the formation o f flavonoids from exogenously supplied L-tyrosine was observed. Under all conditions the relative incorporation rate o f exogenous L-tyrosine was highest for anthocyanins and lowest for C-glyco-sylflavones while within the latter class o f com pounds the luteolinic derivatives orientin and iso-orientin incorporated more label than their apigeninic analogues vitexin and isovitexin. PAL and TAL activities were found to be present in the cotyledons in a ratio o f 50:1. The possible role o f L-tyrosine as an alternative natural precursor for the biosynthesis o f flavonoids and other related polyphenols is discussed. 
  Reference    Z. Naturforsch. 40c, 154 (1985); received April 24/O ctober 29 1984 
  Published    1985 
  Keywords    Anthocyanins, Flavonoids, Biosynthesis, [14C-L]Tyrosine, [14C-L]Phenylalanine, Kinetin, Glyphosate, Fagopyrum esculentum 
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 TEI-XML for    default:Reihe_C/40/ZNC-1985-40c-0154.pdf 
 Identifier    ZNC-1985-40c-0154 
 Volume    40