Research article

Long-distance transport of L-ascorbic acid in potato

Luigi Tedone^1,2 , Robert D Hancock¹ , Salvatore Alberino^1,3 , Sophie Haupt¹ and Roberto Viola¹

¹Unit of Plant Biochemistry, Scottish Crop Research Institute, Invergowrie, Dundee DD2 5DA, UK

²Dipartimento di Scienze delle Produzioni Vegetali, Universita degli Studi di Bari, Italy

³University of Naples "Federico II", Department of Soil, Plant and Environmental Sciences, Via Universita' 100 – 80055 Portici, Italy

author email corresponding author email

BMC Plant Biology 2004, 4:16doi:10.1186/1471-2229-4-16

Published:	17 September 2004

Abstract

Background

Following on from recent advances in plant AsA biosynthesis there is increasing interest in elucidating the factors contributing to the L-ascorbic acid (AsA) content of edible crops. One main objective is to establish whether in sink organs such as fruits and tubers, AsA is synthesised in situ from imported photoassimilates or synthesised in source tissues and translocated via the phloem. In the current work we test the hypothesis that long-distance transport is involved in AsA accumulation within the potato tuber, the most significant source of AsA in the European diet.

Results

Using the EDTA exudation technique we confirm the presence of AsA in the phloem of potato plants and demonstrate a correlation between changes in the AsA content of source leaves and that of phloem exudates. Comparison of carboxyflourescein and AgNO₃ staining is suggestive of symplastic unloading of AsA in developing tubers. This hypothesis was further supported by the changes in AsA distribution during tuber development which closely resembled those of imported photoassimilates. Manipulation of leaf AsA content by supply of precursors to source leaves resulted in increased AsA content of developing tubers.

Conclusion

Our data provide strong support to the hypothesis that long-distance transport of AsA occurs in potato. We also show that phloem AsA content and AsA accumulation in sink organs can be directly increased via manipulation of AsA content in the foliage. We are now attempting to establish the quantitative contribution of imported AsA to overall AsA accumulation in developing potato tubers via transgenic approaches.