Sentence:  <WSD>Root</WSD> and stem tumors from sweet clover plants infected with WTV were quick-frozen in liquid nitrogen , embedded in ice , and cut at 3 - 6 | m in a cryostat maintained at - 16 ` to - 20 ` . 
Meaning of the word marked with <WSD> tags:  (botany) the usually underground organ that lacks buds or leaves or nodes; absorbs water and mineral salts; usually it anchors the plant to the ground