Does turgor limit growth in tall trees
Does turgor limit growth in tall trees
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DOI：
10.1111/j.1365-3040.2003.01141.x
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发表时间：
2004-02
影响因子：
7.3
通讯作者：
D. Woodruff;B. Bond;F. Meinzer
中科院分区：
文献类型：
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作者：
D. Woodruff;B. Bond;F. Meinzer
水势的重力分量对植物木质部张力梯度的贡献为0.01 MPa m - 1。在高大的树木中，这种贡献可以显着降低树冠附近的水势。芽和叶中细胞的膨压预期将沿沿着高度梯度与叶水势成正比地降低，除非发生渗透调节。压力-体积技术被用来表征在年轻和年老的道格拉斯冷杉树的叶组织水分关系和新梢生长特性的高度依赖性变化，以确定随着高度增加的生长限制的程度可能与重力水势梯度对叶膨压的影响。在13.5m处的幼叶顶部附近的叶片上估计了叶水势（Yl）、满膨压和零膨压下的整体渗透势以及其他关键的组织水分关系特征（约25岁）的树木和34.7，44.2和55.6米的老生长（约450岁）的树木在连续三个生长季节的部分树冠。取样期与芽的膨大、扩展和新叶的成熟期相吻合。垂直梯度的Yl和压力-体积分析表明，膨压随着高度的增加而下降，特别是在晚春营养芽开始膨胀时。分支伸长，叶面积和叶质量的垂直趋势是一致的，随着高度的增加，增加膨压限制地上部生长。在晚春（5月），没有渗透调节，以补偿重力梯度的Y 1观察。到7月，渗透调节已经发生，但不足以完全补偿Yl的垂直梯度。在高大的树木中，Y Y Y 1的重力分量叠加在叶水分关系特征的物候驱动的变化上，对膨压施加潜在的限制，这可能与土壤水分亏缺相关的限制无法区分。
The gravitational component of water potential contributes a standing 0.01 MPa m - 1 to the xylem tension gradient in plants. In tall trees, this contribution can significantly reduce the water potential near the tree tops. The turgor of cells in buds and leaves is expected to decrease in direct proportion with leaf water potential along a height gradient unless osmotic adjustment occurs. The pressure‐volume technique was used to characterize height-dependent variation in leaf tissue water relations and shoot growth characteristics in young and old Douglas-fir trees to determine the extent to which growth limitation with increasing height may be linked to the influence of the gravitational water potential gradient on leaf turgor. Values of leaf water potential ( Y l ), bulk osmotic potential at full and zero turgor, and other key tissue water relations characteristics were estimated on foliage obtained at 13.5 m near the tops of young (approximately 25-year-old) trees and at 34.7, 44.2 and 55.6 m in the crowns of old-growth (approximately 450year-old) trees during portions of three consecutive growing seasons. The sampling periods coincided with bud swelling, expansion and maturation of new foliage. Vertical gradients of Y l and pressure‐volume analyses indicated that turgor decreased with increasing height, particularly during the late spring when vegetative buds began to swell. Vertical trends in branch elongation, leaf dimensions and leaf mass per area were consistent with increasing turgor limitation on shoot growth with increasing height. During the late spring (May), no osmotic adjustment to compensate for the gravitational gradient of Y l was observed. By July, osmotic adjustment had occurred, but it was not sufficient to fully compensate for the vertical gradient of Y l . In tall trees, the gravitational component of Y Y Y l is superimposed on phenologically driven changes in leaf water relations characteristics, imposing potential constraints on turgor that may be indistinguishable from those associated with soil water deficits.