Shimazaki Yumi, Ookawa Taiichiro, Hirasawa Tadashi
Graduate School of Agriculture, Tokyo University of Agriculture and Technology, Fuchu, Japan.
Plant Physiol. 2005 Sep;139(1):458-65. doi: 10.1104/pp.105.062091. Epub 2005 Aug 12.
To identify the region in which a root perceives a decrease in the ambient water potential and changes its elongation rate, we applied two agar blocks (1 x 1 x 1 mm(3)) with low water potential bilaterally to primary roots of maize (Zea mays) at various positions along the root. When agar blocks with a water potential of -1.60 MPa (-1.60-MPa blocks) or lower were attached to a root tip, the rate of elongation decreased. This decrease did not result from any changes in the water status of elongating cells and was not reversed when the -1.60-MPa blocks were replaced by -0.03-MPa blocks. The rate decreased slightly and was unaffected, respectively, when -1.60-MPa blocks were applied to the so-called decelerating region of the elongating zone and the mature region. However, the rate decreased markedly and did not recover for several hours at least when such blocks were attached to the accelerating region. In this case, the turgor pressure of the elongating cells decreased immediately after the application of the blocks and recovered thereafter. The decrease in elongation rate caused by -1.60-MPa blocks applied to the root tip was unaffected by additional -0.03-MPa blocks applied to the accelerating region and vice versa. We concluded that a significant reduction in root growth could be induced by water stress at the root tip, as well as in the accelerating region of the elongating zone, and that transmission of some signal from these regions to the decelerating region might contribute to the suppression of cell elongation in the elongation region.
为了确定根感知环境水势降低并改变其伸长速率的区域，我们将两个水势较低的琼脂块（1×1×1立方毫米）双侧施加到玉米（Zea mays）初生根沿根的不同位置。当水势为-1.60兆帕的琼脂块（-1.60兆帕琼脂块）或更低水势的琼脂块附着在根尖时，伸长速率降低。这种降低并非由伸长细胞的水分状态变化引起，并且当-1.60兆帕琼脂块被-0.03兆帕琼脂块替换时也不会逆转。当将-1.60兆帕琼脂块应用于伸长区的所谓减速区和成熟区时，伸长速率分别略有降低且不受影响。然而，当将此类琼脂块附着在加速区时，伸长速率显著降低且至少数小时内无法恢复。在这种情况下，施加琼脂块后伸长细胞的膨压立即降低，随后恢复。施加到根尖的-1.60兆帕琼脂块引起的伸长速率降低不受施加到加速区的额外-0.03兆帕琼脂块的影响，反之亦然。我们得出结论，根尖以及伸长区的加速区的水分胁迫可诱导根生长显著降低，并且从这些区域向减速区传递某些信号可能有助于抑制伸长区的细胞伸长。
