定向选择就是指生存环境的方向性选择（自然选择）或品种的人工定向选择。自然选择在一定程度上是随机的，但也绝非漫无方向，它与生存环境、生态功能以及生物的体制等均息息相关。
在行为实验中发现，挥发性次生代谢物能够影响亚洲玉米螟一龄幼虫的定向选择和成虫的产卵行为。
Large amount of volatile secondary metabolites were also induced by the feeding of Asian Corn Borer larvae.
因此在耐热育种中单纯利用杂交优势试图获得超亲优势来显著提高耐热性是不现实的，而应该注重耐热亲本的定向选择。
So it is not practical to improve the heat resistance significantly in breeding by heterosis, but it is supposed to select the heat tolerant parent in breeding.
是许多私人分享服务产品中的一个。这些产品在你上传——一幅图片，一个视频，等等任何一个文件后，你可以通过一个特别的URL来定向选择分享文件的朋友或同事。
It's one of many new "private sharing" services that let you upload a file-a picture, a video, whatever-and get a special URL you can give to select friends or workmates.
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