Harper Frances A, Smith Suzanne E, Macnair Mark R
Department of Biological Sciences, Hatherly Laboratories, University of Exeter, Prince of Wales Road, Exeter EX4 4PS, UK.
To whom correspondence should be sent at present address.
New Phytol. 1998 Dec;140(4):637-654. doi: 10.1046/j.1469-8137.1998.00312.x.
Circumstantial evidence suggests that plants that have evolved metal tolerance are at a disadvantage on normal soil, i.e. there is a cost of tolerance. One hypothesis for the cause of this cost is that individuals have a greater requirement for copper, and so suffer micronutrient deficiency on normal soils, as a result of a reduced uptake, distribution and/or utilization of copper. We provided highly and less copper-tolerant plants of Mimulus guttatus Fischer ex DC. (the common monkey flower) with sub-optimal copper, and demonstrated the importance of copper as an essential micronutrient during the reproductive phase, both in the production of viable pollen and in seed set. We also looked at the effect of sub-optimal copper supply on the growth of the microgametophyte, and the efficiency with which seed was set. No evidence was found that highly tolerant plants have an increased copper requirement during the reproductive phase. This is in agreement with earlier work on Mimulus guttatus, which investigated the copper requirement of highly tolerant plants during vegetative growth and found that any differences in copper requirement were small. The 'metal requirement hypothesis' is, therefore, not the sole explanation for the cost of copper tolerance in M. guttatus.
间接证据表明，已经进化出金属耐受性的植物在正常土壤上处于劣势，即存在耐受性代价。对于这种代价产生的原因，一种假设是个体对铜有更高的需求，因此在正常土壤上由于铜的吸收、分配和/或利用减少而遭受微量营养素缺乏。我们为铜耐受性高和低的黄花沟酸浆（普通猴面花）提供了次优铜水平，并证明了铜作为生殖阶段必需微量营养素在产生可育花粉和结实方面的重要性。我们还研究了次优铜供应对小配子体生长以及结实效率的影响。没有发现证据表明高耐受性植物在生殖阶段对铜的需求增加。这与早期对黄花沟酸浆的研究一致，该研究调查了高耐受性植物在营养生长期间对铜的需求，发现铜需求的任何差异都很小。因此，“金属需求假说”不是黄花沟酸浆铜耐受性代价的唯一解释。
