Root and stem xylem embolism, stomatal conductance, and leaf turgor in Acer grandidentatum populations along a soil moisture gradient
Root and stem xylem embolism, stomatal conductance, and leaf turgor in Acer grandidentatum populations along a soil moisture gradient
复制标题
DOI：
10.1007/bf00328731
复制
发表时间：
1996-02-01
期刊：
影响因子：
2.7
通讯作者：
Pockman, WT
中科院分区：
文献类型：
--
作者：
Alder, NN;Sperry, JS;Pockman, WT
研究了大齿槭（Acer grandidentum Nutt）河岸（湿）和相邻坡地（干）种群气孔导度（g（s））和膨压损失点（Psi（tlp））的调节作用。与根和茎木质部对栓塞的敏感性有关。在两个夏天的研究（1993-1994年），斜坡网站的木质部压力（PSI（PX））和g（S）比河岸网站，特别是在干旱的1994年。Psi（tlp）在斜坡处（-2.9 +/- 0.1 MPa;所有误差95%置信限）也低于河岸站点（-1.9 +/- 0.2 MPa）;但它并未因1994年干旱而下降。茎木质部没有不同的脆弱性栓塞之间的网站。虽然在1994年的干旱中，坡地茎比河岸茎失去了更大比例的水力传导性栓塞（46 +/- 11%对27 +/- 3%），他们仍然保持了至少1.7 MPa的安全裕度之间的中午PSI（px）和临界压力触发灾难性木质部栓塞（PSI（pxCT））。根木质部比茎木质部更容易发生栓塞，并且不同地点之间存在显著差异：河岸根在-1.75 MPa下完全空化，而斜坡根在-2.75 MPa下完全空化。栓塞的脆弱性与血管间小凹膜的孔径有关，而与血管直径没有简单的关系。从PSI（pxCT）的安全裕度平均小于0.6 MPa的根在河岸和斜坡网站。在1994年干旱期间，斜坡位置的最小安全裕度可能导致气孔几乎完全关闭（g（s）= 9 +/- 2对河岸位置的79 +/- 15 mmol m（-2）s（-1）），并使Psi（tlp）的任何进一步渗透调节非适应性。在秋季降雨后，根部栓塞至少部分逆转。虽然灾难性的栓塞在根可能会限制最低PSI的气体交换，部分（和可逆）根栓塞可能是自适应的限制水的使用，土壤水耗尽。
The objective of this study was to determine how adjustment in stomatal conductance (g(s)) and turgor loss point (Psi(tlp)) between riparian (wet) and neighboring slope (dry) populations of Acer grandidentum Nutt. was associated with the susceptibility of root versus stem xylem to embolism. Over two summers of study (1993-1994), the slope site had substantially lower xylem pressures (Psi(px)) and g(s) than the riparian site, particularly during the drought year of 1994. The Psi(tlp) was also lower at the slope (-2.9 +/- 0.1 MPa; all errors 95% confidence limits) than at riparian sites (-1.9 +/- 0.2 MPa); but it did not drop in response to the 1994 drought. Stem xylem did not differ in vulnerability to embolism between sites. Although slope-site stems lost a greater percentage of hydraulic conductance to embolism than riparian stems during the 1994 drought (46 +/- 11% versus 27 +/- 3%), they still maintained a safety margin of at least 1.7 MPa between midday Psi(px) and the critical pressure triggering catastrophic xylem embolism (Psi(pxCT)). Root xylem was more susceptible to embolism than stem xylem, and there were significant differences between sites: riparian roots were completely cavitated at -1.75 MPa, compared with -2.75 MPa for slope roots. Vulnerability to embolism was related to pore sizes in intervessel pit membranes and bore no simple relationship to vessel diameter. Safety margins from Psi(pxCT) averaged less than 0.6 MPa in roots at both the riparian and slope sites. Minimal safety margins at the slope site during the drought of 1994 may have led to the almost complete closure of stomata (g(s) = 9 +/- 2 versus 79 +/- 15 mmol m(-2) s(-1) at riparian site) and made any further osmotic adjustment of Psi(tlp) non-adaptive. Embolism in roots was at least partially reversed after fall rains. Although catastrophic embolism in roots may limit the minimum Psi for gas exchange, partial (and reversible) root embolism may be adaptive in limiting water use as soil water is exhausted.