Figure 2.

Systematic adaptive responses caused by flooding and drought stress. (A) During prolonged drought, exposure plants increase the initiation of adventitious roots as indicated in this simplified model. This initiation is induced by the inhibition of PIN2, decreasing auxin transport from shoot to root. The accumulation of indole-3-acetic acid (IAA) in the stem causes the induction of LBD16 (through auxin response factors [ARFs]) and the subsequent initiation of adventitious roots. (B) During long drought periods, plants accumulate abscisic acid (ABA) in leaf tissue. This accumulation leads to regulation of multiple genes of which one is the transcription factor MYB96. Through MYB96 induction, ABA regulates gene expression of RD22 and GH3. RD22 is important for drought responses in the shoot by modulating stomatal aperture. GH3 promotes conjugation of IAA in the root, thereby limiting auxin levels and restricting the initiation and development of lateral roots.