Aquaporins are required for the germination of orthodox seeds through affecting vacuolation and α-amylase activity. During seed germination, vacuolation occurs. TIP3s are enriched in small protein storage vacuoles (PSVs), whereas TIP1s accumulate in large vacuoles (LV). TIP3s negatively affect the formation of LVs. Gibberellins (GAs) activate α-amylase activity and promote the conversion of PSVs to LVs by inhibiting HvTIP3;1 expression, but abscisic acid (ABA) has the opposite effect during barley seed germination [38]. AtTIP3;1 and AtTIP4;1 have positive effects, whereas AtTIP3;2 has negative effects on ABA-inhibited seed germination [39]. Rice OsPIP1;1 has a beneficial role in seed germination by inducing α-amylase activity, and OsPIP1;3 plays a positive role during seed germination [35]. Long solid arrows show the transition of seed germination, and short and thick up arrows indicate increases in the abundance of HvTIP3;1 and the activities of α-amylase. Short and thin solid arrows reveal positive regulation, and bars represent negative regulation. The dotted arrow represents unidentified regulation and the gray in PSVs shows the storage nutrients.