Hoffmann-Benning S., Kende H.
Michigan State University-Department of Energy Plant Research Laboratory, Michigan State University, East Lansing, Michigan 48824-1312.
Plant Physiol. 1994 Feb;104(2):719-723. doi: 10.1104/pp.104.2.719.
Submergence induces rapid elongation of deepwater rice (Oryza sativa L.) internodes. This adaptive feature allows deepwater rice to grow out of the water and to survive flooding. The growth response of submerged deepwater rice plants is, ultimately, elicited by gibberellin (GA). Little attention has been given to the synthesis and role of the cuticle during plant growth. We investigated two questions regarding the cuticle in rapidly elongating deepwater rice internodes: (a) how does cuticle formation keep pace with internodal growth, which can reach rates of up to 5 mm/h; and (b) does the cuticle contribute to tissue stress in rice internodes? Treatment with GA for 48 h caused an up to 60-fold increase in the incorporation of [14C]palmitic acid and an up to 6-fold increase in the incorporation of [14C]oleic acid into the cuticle of growing internodes. GA also caused a qualitative change in the incorporation pattern of palmitic acid into several cutin monomers, the most prominent of which was tentatively identified by thin-layer chromatography as a derivative of dihydroxyhexadecanoic acid. Rapidly growing plant organs exhibit longitudinal tissue stress: the epidermal cell layer is under tension with a tendency to contract, whereas the internal cells are under compression with a tendency to expand. As a result of tissue stress, longitudinally sliced sections of elongating internodes bend outward upon isolation from the plant. Treating rapidly growing rice internodes with cutinase reduced such outward bending, indicating that the cuticle contributes to tissue stress. Based on these results, we propose that rapidly elongating structures such as deepwater rice internodes constitute an excellent system to study cuticle formation at the biochemical and cellular level.
淹水会诱导深水水稻（Oryza sativa L.）节间迅速伸长。这一适应性特征使深水水稻能够长出水面并在洪水中存活。淹水的深水水稻植株的生长反应最终是由赤霉素（GA）引发的。在植物生长过程中，角质层的合成及其作用很少受到关注。我们研究了关于快速伸长的深水水稻节间角质层的两个问题：（a）角质层形成如何跟上节间生长的速度，节间生长速度可达每小时5毫米；（b）角质层是否会导致水稻节间的组织应力？用GA处理48小时导致[14C]棕榈酸掺入生长节间角质层的量增加高达60倍，[14C]油酸掺入量增加高达6倍。GA还导致棕榈酸掺入几种角质单体的模式发生质的变化，其中最显著的经薄层色谱初步鉴定为二羟基十六烷酸的衍生物。快速生长的植物器官表现出纵向组织应力：表皮细胞层处于张力状态并有收缩的趋势，而内部细胞处于压缩状态并有扩张的趋势。由于组织应力，伸长节间的纵向切片在从植株分离后会向外弯曲。用角质酶处理快速生长的水稻节间可减少这种向外弯曲，表明角质层会导致组织应力。基于这些结果，我们提出，像深水水稻节间这样快速伸长的结构构成了一个在生化和细胞水平上研究角质层形成的极佳系统。
