Similar behavior, different mechanisms: the research of the style bending of Alpinia species

Abstract

The styles of the plants of genus Alpinia show a similar bending behavior. Each species has two types—hyper-type and cata-type. The styles of hyper-type bend downward first, and then bend upward second. The styles of cata-type also bend twice, but the bending direction is opposite to hyper-type. We tested the effects of light, IAA, and NPA on the style movement of Alpinia oxyphylla and Alpinia galanga, and analyzed the IAA distribution in their styles. We found that the effects of light were similar for the two species, but the two types of each species responded differently. The first style bending of hyper-type was downward when it was in dark, and was upward when in light; the second bending was upward if in light, and did not move if in dark. The two bendings of cata-type showed no obvious difference between in dark and in light. Effects of IAA and NPA were different for two species. For A. galanga, neither IAA nor NPA had obvious effects on the style bending. For A. oxyphylla, IAA enhanced the second bending of hyper-type and the two bendings of cata-type. NPA enhanced the second bending of hyper-type and the first bendings of cata-type, and significantly inhibited the second bending of cata-type. The results of IAA immunolocalization indicated that IAA was symmetrical in the styles of A. galanga both before the first bending and before the second bending in two types. However, in A. oxyphylla, IAA asymmetry was found in two types. Therefore, we hypothesize that the mechanisms of the style bending of Alpinia plants are different, not only between two types of each species, but also among species.