Influence of boron deficiency on 3H indole-3yl-acetic acid uptake and efflux in cell cultures of Daucus carota L.

³H-IAA net uptake and efflux was measured in carrot cell suspensions after two and five days in either boron (B) sufficient or B deficient media. Contrary to earlier observations with substances such as phosphate, glucose and potassium (or Rb⁺), ³H-label uptake from IAA over a 3 h period did not differ significantly after two days of treatment. After five days of B deficiency, cells accumulated higher ³H-activity than those receiving B. Total ³H-efflux from deficient and sufficient cells did not differ significantly but B deficient cells released more water soluble (pH 3.0) ³H, and less methanol soluble ³H activity, which may be due to a higher IAA oxidase activity. Correspondingly, we found an elevated peroxidase (POD) activity in B deficient cell cultures which was 54% higher after two days of deficieny and which increased further threefold after five days. Similar changes have been found in the amount of POD activity released to the nutrient solution with even more pronounced differences after two days. Thus, B deficient cells released less authentic ³H-IAA (1.7% vs. 3.1% related to total ³H efflux), as determined by HPLC separation.