Distribution of Plant Hormones and Their Precursors in Cambial Region Tissues of Quercus myrsinifolia and Castanopsis cuspidata var.sieboldii after Bending Stems or Applying Ethylene precursor

The role of plant hormones in tension wood (TW) formation has been studied but is still unclear. IAA, ABA, ACC, tZ, tZR, iP, and iPR in cambial region tissues were identified and quantified by liquid chromatography/mass spectrometry (LC/MS). We examined the distribution of plant hormones and their precursors in the stems of Quercus myrsinifolia Blume and Castanopsis cuspidata var.sieboldii Nakai after bending the stems or applying an ethylene precursor (ACC). After 3 weeks of bending, though not after 1 week of bending, the auxin (IAA) and abscisic acid (ABA) amounts were larger on the TW side than on the opposite wood (OW) side and in upright trees. After 2 weeks of bending, the peak concentrations of IAA in cambium on the TW side were obviously higher than those on the OW side. After 1 week of bending, the ACC amounts on both sides were larger than in upright trees, but after 3 weeks of bending, they were smaller than in upright trees. Applied ACC did not enhance TW formation but induced axical parenchyma and phloem formation in C. cuspidata var.sieboldii. These results indicated that the distribution patterns of IAA and ABA might have important roles in TW formation in these two species. The role of ACC might be limited in the early stages of TW formation.