Question

How does the level of development of vascular tissue in the mosses indicate their evolution and overall relatedness to the liverworts and hornworts?

Answer 1

Non-vascular plants also called bryophytes reproduce without seeds. This group include mosses, liverworts and hornworts.

Land plants or embryophytes are classified into two types according to the presence or absence of vascular tissue such as xylem and phloem.

Plants that lack vascular tissue, which contain specialized cells for the transport of water and nutrients are called non-vascular plants or bryophytes. Non-vascular plants probably appeared early in land plant evolution and are all seedless. Mosses, liverworts and hornworts are all non-vascular embryophytes.

Within the bryophytes the three lineages show progressive development of body structure. Liver worts have the most simple organization, hornworts the intermediate and the mosses with most specialized thalli. Mosses have simple water and food conductive cells and lack lignified cell walls. They absorb water from the surface by capillary action. The leaves of liverworts and mosses are undifferentiated and lack stomata.The moss stem lack vascular tissues.