Bryophytes

Question 1

Bryophyte Gametophytes

Answer 1

*In all three bryophyte phyla, gametophytes are larger and longer-living than sporophytes
*Sporophytes are typically present only part of the time

Question 2

Gametophyte growth

Answer 2

A spore germinates into a gametophyte composed of a protonema and gamete-producing gametophore
*Gametangia typically near shoot tips, sometimes on stalked antheridiophores/ archegoniophores
*Rhizoids anchor gametophytes to substrate
*The height of gametophytes is constrained by lack of vascular tissues
*Mature gametophytes produce flagellated sperm in antheridia and an egg in each archegonium
*Sperm swim through a film of water to reach and fertilize the egg

Question 3

Bryophyte Sporophytes

Answer 3

*Bryophyte sporophytes grow out of archegonia and are the smallest and simplest sporophytes of all extant plant groups
*A sporophyte consists of a foot, a seta (stalk), and a sporangium, also called a capsule, which discharges spores through a peristome
*Hornwort and moss sporophytes have stomata for gas exchange
*Lifestyles strongly influenced by moisture availability

Question 4

Moisture dependence

Answer 4

*Water taken up via leaves or rhizoids
*Most water conduction external
*Some bryophytes have conducting cells, but these are unlignified

Question 5

Why are there no large bryophytes?

Answer 5

*Sperms need to be able to swim from the antheridia to the archegonia (on shoot tips)
*Lack of structures to access deep soil water and to provide anchorage
*Lack lignified water-conducting element

Question 6

The Ecological and Economic Importance of Mosses

Answer 6

*Mosses are capable of inhabiting diverse and sometimes extreme environments but are especially common in moist forests and wetlands
Some mosses might help retain nitrogen in the soilSphagnum, or “peat moss,” forms extensive deposits of partially decayed organic material known as peat
*Sphagnum is an important global reservoir of organic carbon

Question 7

Tracheophytes

Answer 7

Tracheophyta = ‘vessel’ plants = vascular plants
*Three bryophyte lineages differentiated comparatively soon (i.e. within 50 million years) after the occupation of land
*tracheophytes possess lignified conducting tissues
*Generally larger than bryophytes (exceptions