Sodium in Recirculating Systems
Sodium did not need to be in the presence of chloride to be detrimental to roses in solution culture. The detrimental effects of sodium were cumulative over successive crop cycles. Increased EC was not the sole cause of plant damage. Some damage may be avoided by the plant by its ability to store sodium in the lower leaves and stems. High sodium concentrations significantly reduced the uptake of potassium. Plants seem to be greener when initially exposed to high sodium concentrations in the nutrient solution. The next step was to study the effects of sodium salts on the net carbon exchange rate of roses grown in solution culture.
In general, data suggested that high levels of salt in the nutrient solution was tolerated by roses, in the short term, with no reduction in the photosynthetic capacity. In fact, in some cases the addition of salts to the solution increased the photosynthetic rate above control levels. However, if high levels of salt were maintained for longer periods, detrimental effect began to be apparent with reduction of photosynthesis and damage to foliage.