Both healthy plant and pathogen-free plant had not these symptoms, yet there were some different in tissue differentiation of both.

健株和脱病植株地上部营养器官均不存在上述症状，但两者在组织结构分化程度上有所区别。

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The techniques included new methods to identify viruses in sweet potato roots, and better systems for multiplying improved virus-free plant varieties.

这些技术包括辨认甘薯根内病毒的新方法以及扩大经改良无病毒作物品种的更好方法。

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Use one year old virus-free plant of hops as cuttings, studies the effect of NAA, Diameter of cuttings and pitch Numbers on hops virus-free plant greenwood cuttings Rooting.

采用啤酒花脱毒苗一年生枝条作插条，研究了插条粗度、节数与NAA对啤酒花脱毒苗绿枝扦插生根的影响。

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It is the kind of technology that could make possible the elusive emission-free power plant.

CNN: Energy debate may soon turn on 'cleaner' coal

American tea-meisters now travel the world seeking the best-nurtured, hand-harvested, pesticide-free leaves of the tea plant.

NPR: Tea for You and Me

If all goes well, and if the test results are verified to the state government's satisfaction by a third-party auditor, which should happen within a few weeks, the plant will begin trucking mountains of used and otherwise useless (but free) cocoa-bean shells to the plant early next year.

ECONOMIST: An unusual energy source gets a try-out