text: An experiment using Chara provided evidence for the pressure-based model of the impact of this phenomenon, by which it can reverse the polarity of cytoplasmic streaming.
full_question: An experiment using Chara provided evidence for the pressure-based model of the impact of this phenomenon, by which it can reverse the polarity of cytoplasmic streaming. This phenomenon is perceived by a specialized variety of amyloplast in statolith cells, which then redirects auxins laterally away from the elongation zone. Generally, roots grow in the direction of this phenomenon, while stems grow in the opposite direction of this phenomenon. This phenomenon that, like light, names a “tropism” that prominently shapes plant development. For 10 points, name this fundamental force that pulls plants (and everything else on Earth) downward.
first_sentence: An experiment using Chara provided evidence for the pressure-based model of the impact of this phenomenon, by which it can reverse the polarity of cytoplasmic streaming.