Pritchard Jeremy, Tomos A Deri, Farrar John F, Minchin Peter E H, Gould Nick, Paul Matthew J, MacRae Elspeth A, Ferrieri Richard A, Gray Dennis W, Thorpe Michael R
School of Biosciences, University of Birmingham, Edgbaston, Birmingham B15 2TT, UK.
Ysgol Gwyddorau Bioleg, Prifysgol Cymru Bangor, Bangor, Gwynedd, LL57 2UW, Wales, UK.
Funct Plant Biol. 2004 Dec;31(11):1095-1103. doi: 10.1071/FP04082.
It has been observed that extension growth in maize roots is almost stopped by exposure to 5 mm d-galactose in the root medium, while the import of recent photoassimilate into the entire root system is temporarily promoted by the same treatment. The aim of this study was to reconcile these two apparently incompatible observations. We examined events near the root tip before and after galactose treatment since the tip region is the site of elongation and of high carbon deposition in the root. The treatment rapidly decreased root extension along the whole growing zone. In contrast, turgor pressure, measured directly with the pressure probe in the cortical cells of the growing zone, rapidly increased by 0.15 MPa within the first hour following treatment, and the increase was maintained over the following 24 h. Both tensiometric measurements and a comparison of turgor pressure with local growth rate demonstrated that a rapid tightening of the cell wall caused the reduction in growth. Single cell sampling showed cell osmotic pressure increased by 0.3 MPa owing to accumulation of both organic and inorganic solutes. The corresponding change in cell water potential was a rise from -0.18 MPa to approximately zero. More mature cells at 14 mm from the root tip (just outside the growing region) showed a qualitatively similar response.
据观察，将玉米根置于含有5毫米D-半乳糖的根培养基中时，根的伸长生长几乎停止，而同样的处理却会暂时促进近期光合产物向整个根系的输入。本研究的目的是调和这两个明显相互矛盾的观察结果。由于根尖区域是根伸长和高碳沉积的部位，我们检查了半乳糖处理前后根尖附近的情况。该处理迅速降低了整个生长区的根伸长。相反，用压力探针直接测量生长区皮层细胞的膨压，在处理后的第一小时内迅速增加了0.15兆帕，并在随后的24小时内保持增加。张力测量以及膨压与局部生长速率的比较均表明，细胞壁的迅速收紧导致了生长的降低。单细胞取样显示，由于有机和无机溶质的积累，细胞渗透压增加了0.3兆帕。细胞水势相应的变化是从-0.18兆帕上升到大约零。距离根尖14毫米处（刚好在生长区域之外）的更成熟细胞表现出定性相似的反应。
