Pit membrane porosity and water stress-induced cavitation in four co-existing dry rainforest tree species
Pit membrane porosity and water stress-induced cavitation in four co-existing dry rainforest tree species
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DOI：
10.1104/pp.014100
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发表时间：
2003-01-01
期刊：
影响因子：
7.4
通讯作者：
Holtum, J
中科院分区：
文献类型：
--
作者：
Choat, B;Ball, M;Holtum, J
研究了干旱-落叶植物南方短壳藻Brachychiton australis(Schott和Endl.)的木质部解剖和对水分胁迫诱导的栓塞病的脆弱性。A.Terracc.和Cochlosperum gillivraei Bth.和两个常绿种Alphitonia exelsa(Fenzal)Bth.和金星天牛Austromyrtus bitwillii(Bth.)Burret.生长在季节性干燥的雨林中。落叶树种更容易受到水分胁迫诱导的木质部栓塞的影响。在-3.17 Mpa和-1.44 Mpa下，澳大利亚白杨和黄杨的渗透系数损失了50%，在-5.56 Mpa和-5.12 Mpa时，白杨和白杨的渗透系数损失了50%。为了确定坑膜孔洞是否导致更易发生栓塞症(空气播种假说)，我们检查了坑膜结构。预期的孔大小是根据脆弱性曲线计算出来的；然而，使用扫描电子显微镜没有检测到预测的孔大小的种间差异(孔在20 nm的分辨率下看不到)。然后，将胶体金颗粒悬浮液通过分支部分进行灌流。这些实验表明，这四个物种的坑膜孔直径都在5到20 nm之间。结果可以用三种可能性来解释：(A)不存在预期大小范围的孔，(B)存在较大的孔，该大小范围内的孔导致空气播撒，但足够罕见，以避免被检测，或(C)只有在由于拉伸/弯曲而使膜处于机械应力(在空气播种期间)时，才会产生预期范围的孔大小。
Aspects of xylem anatomy and vulnerability to water stress-induced embolism were examined in stems of two drought-deciduous species, Brachychiton australis (Schott and Endl.) A. Terracc. and Cochlospermum gillivraei Benth., and two evergreen species, Alphitonia excelsa (Fenzal) Benth. and Austromyrtus bidwillii (Benth.) Burret., growing in a seasonally dry rainforest. The deciduous species were more vulnerable to water stress-induced xylem embolism. B. australis and C. gillivraei reached a 50% loss of hydraulic conductivity at -3.17 MPa and -1.44 MPa, respectively; a 50% loss of hydraulic conductivity occurred at -5.56 MPa in A. excelsa and -5.12 MPa in A. bidwillii. To determine whether pit membrane porosity was responsible for greater vulnerability to embolism (air seeding hypothesis), pit membrane structure was examined. Expected pore sizes were calculated from vulnerability curves; however, the predicted inter-specific variation in pore sizes was not detected using scanning electron microscopy (pores were not visible to a resolution of 20 nm). Suspensions of colloidal gold particles were then perfused through branch sections. These experiments indicated that pit membrane pores were between 5 and 20 nm in diameter in all four species. The results may be explained by three possibilities: (a) the pores of the expected size range were not present, (b) larger pores, within the size range to cause air seeding, were present but were rare enough to avoid detection, or (c) pore sizes in the expected range only develop while the membrane is under mechanical stress (during air seeding) due to stretching/ flexing.