Bryophyta Flashcards
Basic features of bryophytes. (5)
- Display mat like growth, they have a flat thallus which may be errect or thalloid.
- As it is a lower group it displays dichotomous branching and the presence of chlorophyll.
- Some species can grow up to 60 cm.
- Typically found in gametophytic stage ie. dominant stage.
- Vasculature absent in primitive errect bryophytes - hydroid is water conducting and leptoid is food conducting.
Distribution of bryophytes.
Require high levels of moisture to complete their life cycle. Favours high altitude, tropical, sub tropical and temprate regions due to the access to moisture, shade and hard substratum.
Types of reproduction in bryophytes.
- Vegetative
- Sexual
- Asexual - spores
Types of vegetative reproduction (10)
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- Fragmentation
- Tubers
- Gemmae
- Adventatious branches
- Cladia
- Protonema
- Innovations
- Persistent apices
- Bulbis
- Apospory
What is fragmentation?
Thallus may decay to dichotomous branches which causes fragments at junction or fragments may be formed by accidental breakage.
Thallus grows from fragmented thallus.
Ex: Liverworts
What are tubers?
Thallus cell and reserve food material is surrounded by layered protective covering - formed during unfavourable conditions (perinating structures). Observed at peripheral tip of thallus.
Ex: Anthoceros
What are Gemmae?
Structure called gemmae cup holds gemmae - 8 shaped vegitative structure. On its periphary is a fringe. Easier method of reproduction, thus formed during favourable conditions as water is a physical means of releasing gemmae.
Ex: Marchantia
What are adventatious branches?
From underneath the center region of the thallus new branches arise from the old thallus. These branches may detach or continue to extend.
Ex: Hornworts
What is protonema?
These are errect bryophytes whose sporophytes produce spores which on germination forms a filamentous structure. Creepin branches formed on substratum. Primary protonema gives rise to secondary. Multicellular, propogatory, nodal region gives rise to distinguishable parts, may or may not have chlorophyll.
Ex: Funaria
What is the archegonium in bryophytes like?
Female reproductive structure: It is flask shaped - the bulbous bottom is the venter which has a single large egg and a venter canal cell, the other end ie. the neck is lined with jacket cells around 5-8 neck canal cells. The neck and venter disintegrate during maturation due to increased pressure from oozed liquid cellular content is sent to the tip of the neck canal causing cells to open slightly. This substance acts as a chemotactic hormone in the presence of water and attracts male gamete.
What is antheridium in bryophytes like?
Antherozooids are present within and act as male gamete within stalk like structure covere with jacket cells which is dispersed by water causing ostiole breakage releasing gametes.
What is a sporophyte?
An embryo develops into sporophyte ie. asexual entity formed by sexual reproduction. Have a horn like appearance. Errect forms have a capsule conserving spores. Spore mother cell which is haploid forms sporogonium which is diploid undergoes reductional meosis division to form 4 haploid spores.
Explain alternation of generation in bryophytes.
- Haploid spore falls on substratum. - gametophytic stage
- Spore germinates to form hetero or homo thallus.
- Presence of water allows dispersal and fertilization of gametes.
- Zygote formed - sporophytic stage
- Sporophyte formed
- Spore formed
Classification of bryophytes.
DIV: Bryophyta
CLASS: Hepaticopsida Liver wort ex: marchantia
Antherocerotopsida Horn wort ex: antheroceros
Bryopsida mosses ex: funnaria
What is hepaticopsida?
Liver worts. flat thallus which displays dorsiventral diffrentiation branched aseptate thalloid.
Pegged and smooth rhizoids - heterothallic.
Marchantia.
