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Keywords:

  • cotyledon;
  • cysteine;
  • glutathione;
  • Pisum sativum (pea);
  • storage tissue;
  • sulphate;
  • sulphur

Summary

  •  Sulphur export and redistribution from the cotyledons of pea (Pisum sativum) seedlings was investigated to determine the role of cotyledons as a sulphur source during root–shoot axis development.
  •  Thiols and sulphate were analysed using standard biochemical techniques, and 35S fed to cotyledons by injection.
  •  After 35S-cysteine injection, c. 50% of the labelled S in the cotyledon was metabolized to 35S-sulphate. This reaction was partly inhibited by aminooxyacetic acid, an inhibitor of cysteine-desulfhydrase. After 35S-sulphate application, c. 1% of the radiolabel was found in cysteine and glutathione in the cotyledon. After 2 h, c. 20% of the 35S was transported into the root–shoot axis independently of whether 35S-sulphate or 35S-cysteine was injected into the cotyledon. After 4 h, 40% of 35S was found outside the cotyledon.
  •  Cotyledons of pea seedlings are capable of sulphate assimilation and cysteine degradation. Both sulphate and reduced sulphur were allocated from the cotyledons to the developing tissues of the pea seedlings.