TPO5最后一个问题, 我怎么看都觉得2是错的, Though beneficial in lower levels, 这句话和文中提到的 "lower levels会影响植物"相矛盾啊. 希望高手解答一下. 谢谢!
Plantsneed to absorb certain minerals from the soil in adequate quantities for normalgrowth and development. ● ● ● Answer Choices
1. Someplants are able to accumulate extremely high levels of certain minerals andthus
can be used to clean up soilscontaminated with toxic levels of these minerals.
2. Thoughbeneficial in lower levels, high levels of salts, other minerals, and heavymetals can be harmful to plants.
3. Whenplants do not absorb sufficient amounts of essential minerals, characteristicabnormalities result.
4. Becausehigh concentrations of sodium chloride and other salts limit growth in mostplants, much research has been done in an effort to develop salt-tolerantagricultural crops.
5. Someplants can tolerate comparatively low levels of certain minerals, but suchplants are of little use for recycling nutrients back into depleted soils.
6. Mineraldeficiencies in many plants can be cured by misting their roots with a nutrientsolution or by transferring the plants to a soilless nutrient solution.