of the tensiometer. Eventually, the entire tensiometer would become filled with air. This air will increase the time required to reach pressure equilibrium because large volumes of water must move through the porous tip to effect the mass transfer of air through the tip. Thus in order to obtain accurate readings, the water and air are desirably purged periodically from the tensiometer reservoir and replaced with degassed water.
To facilitate purging of air from the tensiometer reservoir, a conventional tensiometer is typically provided with a column of water connecting a surface located pressure measuring device to the soil-embedded porous tip. However, there is a physical limit to the length of a column of water which can be supported by atmospheric pressure (about 1000 cm at sea level), and thePlant genomics: homoplasy heaven in a lycophyte genome.
The recent genomic sequencing of Selaginella, a member of the lycophyte lineage of vascular plants, opens up all kinds of new opportunities to examine the patterns of evolutionary innovation and the creation of the basic bauplan of plants.