from The American Heritage® Dictionary of the English Language, 4th Edition
- n. The first formed xylem that differentiates from the procambium.
from Wiktionary, Creative Commons Attribution/Share-Alike License
- n. The first xylem to form in a plant.
from The Century Dictionary and Cyclopedia
- n. In botany, the first-formed elements of the xylem of a vascular bundle.
The researchers conducted the study in the root of Arabidopsis, a small flowering plant related to cabbage, where they took a closer look at the development of two types of root cells - protoxylem and metaxylem.
High dosage of these messenger RNA molecules lead cells to become metaxylem, whereas low dosage leads to protoxylem.
Using a combination of molecular and cellular techniques including high-resolution imaging, they discovered a complex sequence of events at the molecular level that creates the distinction between protoxylem and metaxylem cells.
Since microRNA 165/6 moves out from its source cells and dissolves their target messenger RNAs, in areas where there are high levels of microRNA 165/6, nearby cells are more likely to become protoxylem.