Uggla C, Mellerowicz EJ, Sundberg B
Department of Forest Genetics and Plant Physiology, Swedish University of Agricultural Sciences, 901 83 Umea, Sweden.
Plant Physiol. 1998 May;117(1):113-21. doi: 10.1104/pp.117.1.113.
The vascular cambium produces secondary xylem and phloem in plants and is responsible for wood formation in forest trees. In this study we used a microscale mass-spectrometry technique coupled with cryosectioning to visualize the radial concentration gradient of endogenous indole-3-acetic acid (IAA) across the cambial meristem and the differentiating derivatives in Scots pine (Pinus sylvestris L.) trees that had different rates of cambial growth. This approach allowed us to investigate the relationship between growth rate and the concentration of endogenous IAA in the dividing cells. We also tested the hypothesis that IAA is a positional signal in xylem development (C. Uggla, T. Moritz, G. Sandberg, B. Sundberg [1996] Proc Natl Acad Sci USA 93: 9282-9286). This idea postulates that the width of the radial concentration gradient of IAA regulates the radial number of dividing cells in the cambial meristem, which is an important component for determining cambial growth rate. The relationship between IAA concentration in the dividing cells and growth rate was poor, although the highest IAA concentration was observed in the fastest-growing cambia. The radial width of the IAA concentration gradient showed a strong correlation with cambial growth rate. The results indicate that IAA gives positional information in plants.
维管形成层在植物中产生次生木质部和韧皮部，并且负责森林树木中的木材形成。在本研究中，我们使用了一种与冷冻切片相结合的微尺度质谱技术，以可视化内源吲哚 - 3 - 乙酸（IAA）在不同形成层生长速率的欧洲赤松（Pinus sylvestris L.）树木的形成层分生组织和分化衍生细胞中的径向浓度梯度。这种方法使我们能够研究生长速率与分裂细胞中内源IAA浓度之间的关系。我们还检验了IAA是木质部发育中的位置信号这一假设（C. 乌格拉、T. 莫里茨、G. 桑德伯格、B. 松德伯格 [1996] 美国国家科学院院刊93: 9282 - 9286）。这一观点假定IAA的径向浓度梯度宽度调节形成层分生组织中分裂细胞的径向数量，而这是决定形成层生长速率的一个重要组成部分。尽管在生长最快的形成层中观察到了最高的IAA浓度，但分裂细胞中的IAA浓度与生长速率之间的关系并不显著。IAA浓度梯度的径向宽度与形成层生长速率呈现出强烈的相关性。结果表明，IAA在植物中提供位置信息。
