Plants have evolved numerous strategies to spread their seeds widely. Some scatter their seeds to the wind, while others tempt animals and birds to eat their seed-filled fruits. And a few rare plants – such as the popping cress Cardamine hirsuta – have evolved exploding seed pods that propel their seeds in all directions. In their new study published in PNAS, Angela Hay and colleagues – from the Max Planck Institute for Plant Breeding Research in Cologne, Germany – investigate what genes control the mechanical structure of these exploding seed pods. Their findings show that a key micronutrient – copper – is essential for laying down a precise pattern of lignin in the seed pods. Lignin is an abundant plant polymer found in lignocellulose, the main structural material in plants. It is present in plant cells walls and is responsible for making wood stiff.
在联邦土地上采矿可以生产黄金、铜、煤炭和磷酸盐等矿产。有几项法律对这种采矿进行了管理。根据联邦土地的类型和生产的矿物种类,矿山运营商可能需要也可能不需要向政府支付特许权使用费
这是我们报告的补充,《联邦土地上的采矿:800多个授权采矿作业和矿产总产量未知》,GAO-20-461。它提供了截至2018年9月30日在联邦土地上授权生产黄金、磷酸盐和煤炭等固体矿产的每个单独作业的额外数据。它还包含授权作业所在的州、主要商品、矿山作业的相关地表英亩数以及作业所在的联邦土地等信息