The influence of ion accumulation on growth and development of roses and chrysanthemums in solution culture
Pending environmental legislation related to control of greenhouse effluent is a significant issue for this industry. This study underscores the importance of understanding the ion accumulations in solution culture. Sodium and chloride tend to be present in catchment ponds and may pose a threat if this water is used for irrigation. High chloride concentrations from potassium chloride, in the irrigation solution for roses had no major detrimental effects on roses in a recirculating system even though foliar levels of chloride reached 6477ppm in the highest chloride treatment. This suggested that chloride may not be the major contributor to salt damage in solution cultured roses. In order to determine if potassium was masking the chloride effects, further experiments using other chloride salts were carried out. High chloride levels from potassium chloride and calcium chloride posed little threat to roses. If however, the chloride is accompanied by sodium potential problems exists. The damage was cumulative over successive crop cycles. Sodium was stored in stems to a much greater extent than in leaves. Sodium was more damaging than chloride and did not need to be in the presence of chloride to be detrimental to roses. The increased EC (electrical conductivity) caused by high salts was not the sole cause of plant damage. Higher concentrations of sodium tended to increase the maximum NCER (net carbon exchange rate) and the LCP (light compensation point) in roses. Most damage was seen on chrysanthemums from the sodium chloride treatment. Damage included significant chlorosis, reduced uptake of calcium, copper and manganese and reduced dry weights. Sodium seemed to be most detrimental. However, chloride was not totally harmless since slightly lower dry weights were also seen in calcium and potassium chloride treatments. Higher sodium concentrations tended to decrease the maximum NCER in chrysanthemums when combined with chloride and to a lesser extent when combined with sulphate. Higher sodium concentrations tended to increase the LCP. Long term production and quality of roses and chrysanthemums was reduced by sodium accumulation in the nutrient solution. Since sodium is often present in water used for irrigation, it is a major ion of concern in solution cultured crops and should be monitored carefully.