Department of Biology, Laurentian University, 935 Ramsey Lake Road, Sudbury, Ontario, Canada.
J Exp Bot. 2012 Oct;63(16):5957-66. doi: 10.1093/jxb/ers241. Epub 2012 Sep 10.
The effects of heavy metal stress, drought stress, and their combination on xylem structure in red maple (Acer rubrum) seedlings were investigated in an outdoor pot experiment. As metal-contaminated substrate, a mixture of 1.5% slag with sand was used, with Ni, Cu, Co, and Cr as the main contaminants. Plants grown on contaminated substrate had increased leaf metal concentrations. The two stresses reduced plant growth in an additive manner. The effects of metal and drought stresses on xylem characteristics were similar to each other, with a reduced proportion of xylem tissue, reduced conduit density in stems, and reduced conduit size in the roots. This resulted, in both stems and roots, in reductions in hydraulic conductance, xylem-specific conductivity, and leaf-specific conductivity. The similarity of the responses to the two stresses suggests that the plants' response to metals was actually a drought response, probably due to the reduced water uptake capacity of the metal-exposed roots. The only plant responses specific to metal stress were decreasing trends of stomatal density and chlorophyll content. In conclusion, the exposure to metals aggravates water stress in an additive manner, making the plants more vulnerable to drought.
重金属胁迫、干旱胁迫及其复合效应对红枫（Acer rubrum）幼苗木质部结构的影响在户外盆栽实验中进行了研究。以 1.5%炉渣和沙的混合物作为金属污染基质，以 Ni、Cu、Co 和 Cr 为主要污染物。在污染基质上生长的植物叶片金属浓度增加。两种胁迫以累加的方式降低植物生长。金属和干旱胁迫对木质部特征的影响相似，木质部组织比例降低，茎干导管密度降低，根导管尺寸减小。这导致在茎和根中，水力传导率、木质部比导率和叶片比导率降低。对两种胁迫的响应相似表明，植物对金属的响应实际上是干旱响应，可能是由于暴露于金属的根的吸水能力降低所致。唯一对金属胁迫特异的植物响应是气孔密度和叶绿素含量呈下降趋势。总之，金属暴露以累加的方式加剧了水分胁迫，使植物更容易受到干旱的影响。
