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Development of pH sensitivity of sucrose uptake during ageing of Vicia faba leaf discs
Author(s) -
Lemoine Remi,
Delrot Serge,
Auger Evelyne
Publication year - 1984
Publication title -
physiologia plantarum
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.351
H-Index - 146
eISSN - 1399-3054
pISSN - 0031-9317
DOI - 10.1111/j.1399-3054.1984.tb05172.x
Subject(s) - vicia faba , spermidine , sucrose , cycloheximide , phloem , ageing , absorption (acoustics) , chemistry , horticulture , botany , biochemistry , biology , protein biosynthesis , enzyme , genetics , physics , acoustics
Uptake of [U‐ 14 C]‐sucrose (40 m M ) by fresh and aged peeled leaf discs of broad bean ( Vicia faba L. cv. Aguadulce) has been studied. In fresh discs, uptake was nearly insensitive to external pH, whereas the pH response of absorption in discs aged for 12 h was bell‐shaped, with an optimum between pH 5 and 6. At this pH, uptake was nearly twice that in fresh tissue. The passive (insensitive to carbonyl cyanide m ‐chlorophenylhydrazone and to cold treatment) uptake was the same in fresh or aged discs. The development of pH sensitivity of absorption did not appear when ageing was performed in the presence of 10 −H M cycloheximide or 5.7 × 10 −5 M actinomycin D. Similarly, when the tissues were treated with 10 −3 M spermidine for 2 h after excision and then aged for 10 h, the development of the pH‐sensitive uptake system was inhibited. Ca 2+ (10 −2 M ) supplied together with spermidine prevented the inhibiting effect of spermidine. The appearance of the pH‐sensitive system was also markedly reduced if ageing took place in the presence of 10 −3 M aminoethoxyvinylglycine. Autoradiographs from fresh discs and from discs aged with or without the inhibitors suggest that pH sensitivity developed more intensively in the parenchyma than in the veins. The results suggest some caution when using excised leaf discs for studies on sucrose uptake and phloem loading. Development of pH sensitivity of uptake may require the synthesis of both DNA‐dependent RNA and protein and could be related to ethylene metabolism.