美国科学60秒 SSS 2013-07-09（在线收听）

 　　Lawn enthusiasts love a lush, green carpet of grass, which is why they hate crabgrass. And now they may have one more reason to despise the weed. Because crabgrass isn't just faster-growing than the rest of lawn. It may actually be poisoning the lawn, by pumping herbicide into the soil. That's according to a study in the Journal of Agricultural and Food Chemistry. Researchers grouped crabgrass hydroponically, so they could easily capture any chemicals released by the plant's roots. Then they dripped that hydroponic solution into pots of wheat, corn and soy bean seedlings. Two weeks later, they dried and weighted the seedlings. And sure enough, the crabgrass solution had significantly stunted the seedlings' growth, compared to control plants. And since corn is in the same family as lawn grasses, the crabgrass toxic effect may also spill bad news for your beautiful Kentucky bluegrass. The researchers still aren't exactly sure how crabgrass' chemical weapons work. But the weed can wipe out beneficial bacteria and fungi in the soil, too. So it's possible crabgrass poisons its neighbors directly, by releasing toxins and indirectly, by creating inhospitable soil. Either way, it's bound to make lawn-owners crabby.