{'fraction_non_alphanumeric': 0.03504482477587612, 'fraction_numerical': 0.023634881825590873, 'mean_word_length': 5.0492610837438425, 'pattern_counts': {'":': 0, '<': 0, '<?xml version=': 0, '>': 0, 'https://': 0, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 0, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
Revisiting auxin transport inhibition as a mode of action for herbicides

SCB-1, a semicarbazone, is a phytotoxin with both preemergence and postemergence activity against broadleaves and grasses. It effectively displaced [3H]naptalam bound to a solubilized plasma membrane fraction, with the concentration required for 50% dissociation being 3.5 nM. The intrinsic dissociation constant (Kd ) for binding of [3H]naptalam to zucchini plasma membranes was estimated to be 9.7 nM. Binding of [3H]naptalam to the solubilized protein fraction from the plasma membrane was rapid, time dependent, saturable, and reversible. The Kd for binding was estimated at 4 nM. Based on the maximum binding of [3H]naptalam, concentration of the binding protein was calculated to be 23.6 and 10.8 pmol mg−1 protein in the plasma membrane and solubilized fraction, respectively. SCB-1 also blocked the efflux of [14C]IAA, resulting in more than 800% accumulation of radiolabel in zucchini squash hypocotyl segments at 5 μM. This accumulation was quenched by excess cold IAA and 2,4-D. Collectively, these results suggest that SCB-1 is a potent inhibitor of auxin efflux and that it competes with naptalam for binding to the plasma membrane protein.