Mosses and Their Relatives Bryophytes Mosses and Their Relatives

Lack true stems, leaves, or roots bryophytes Lack true stems, leaves, or roots Are non-vascular which means they do not have vascular tissues Vascular tissues are specialized to conduct water and nutrients

Grow in almost all biomes: tropical, temperate and polar Since they don’t have vascular tissue, how do they get water and nutrients to all of their cells? They must be in a wet environment Sperm must swim to eggs Need rainfall or dew for at least part of the year They cannot grow very tall No true roots Have rhizoids Long, thin cells that anchor them and absorb water and minerals Water moves through via osmosis Their “leaves” are only one cell layer think to allow for movement of water and minerals Grow in almost all biomes: tropical, temperate and polar

Three groups Mosses Liverworts Hornworts

mosses Most common Grow in swamps, bogs, near streams and rain forests where there is a lot of moisture Well adapted to wet habitats and poor soil Tolerate low temperatures making them the most abundant plant in polar regions  Green part we are familiar with is the gametophyte Thin stalk with capsule at top formed for reproduction is the sporophyte

liverworts Flat plants resembling the shape of a liver Broad, flat, thin structure called gametophyte which draws moisture directly from surface Need damp soil nearly year round Umbrella like structures for reproduction called sporophytes  Some can produce asexually via structures called gemmae Very cool little system Gemmae produced in gemma cup Get washed out of cups and can then reproduce via mitosis

hornworts Similar to liverworts Sporophyte looks like a tiny green horn

Life cycle: part 1 Gametophyte is dominant Easily recognizable Carries out most of the photosynthesis Sporophyte depends on gametophyte to supply water and nutrients  Reproduction cycle is alternation of generations Moss spore germinates (if conditions are correct)  Grows into protonema (look it up!) Rhizoids form that grow into ground Shoots form that grow into air Form gametophyte

Life cycle: part 2 Gametes develop Sperm develop in antheridia Eggs develop in archegonia Depending on species, may have both structures on one plant or on separate plant  Sperm release and swim to egg Fertilization occurs forming diploid zygote Zygote is beginning of sporophyte stage Sporophyte grows out of gametophyte Haploid spores produced in capsule via meiosis When mature, capsule opens, spores released, spread and cycle starts again

Ecology of mosses Natural sponges absorbing large amounts of water Can be used to reduce water loss from plant containers Dead remains accumulate forming thick deposits of peat Useful as fuel Useful in gardens Improves water retention Increases soil acidity which is good for some plants