ISHS Acta Horticulturae 511: XXV International Horticultural Congress, Part 1: Culture Techniques with Special Emphasis on Environmental Implications - Nutrient Management
SODIUM TRANSPORT AND DISTRIBUTION IN SWEET PEPPER DURING AND AFTER SALT STRESS |
| Author: | M. Blom-Zandstra |
| Keywords: | Capsicum annuum L., cultivation strategy, distribution, model, phloem, salinity, sodium transport, sweet pepper, xylem |
| Abstract:
In hydroponic systems often saline water is used in nutrient solutions. Transpiration leads to a steady increase of the salt concentration. To avoid unfavourable salt conditions, solutions are renewed, regularly. So, plants are exposed to varying sodium concentrations. In this paper, the sodium distribution and its transport-profile in sweet pepper (Capsicum annuum L.) under stress conditions and the consequences of transfering the plants to a sodium-free nutrient solution will be discussed. Plants can tolerate sodium stress very well. They appear to keep sodium out of the photosynthetic apparatus efficiently. Sodium is accumulated in the root cells and in the pith cells of the stem, mostly in the basal part. Almost no sodium is directed to the leaves and the fruits. Similar to the sodium profile of the pith cells, the sodium concentration of the xylem sap shows a concentration gradient decreasing towards the tip. A split root experiment, in which a pulse labelling with radioactive sodium was carried out, showed the involvement of phloem transport. During the salt stress period sodium is recirculated between phloem and xylem. Apparently, pith cells, the intermediates between the xylem and phloem veins, play a decisive role in the (re)circulation of sodium through the plant. After transferring the plants to a sodium-free solution a fast release of sodium occurs. In this paper, a model for a general transport mechanism will be presented. The consequences of sodium release into the nutrient solution after a refreshment will be calculated for the situation in greenhouses. | |
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