LAB: Phylum Charophyta: Stoneworts The Charaphytes are a derived group, closely
ID: 38067 • Letter: L
Question
LAB: Phylum Charophyta: Stoneworts
The Charaphytes are a derived group, closely related to the Chlorophyta. They have multicellular gametangia with a sterile jacket of cells making up the walls of the gametangia. This and other adaptations that allow them to tolerate desiccation differentiate them from the Chlorophyta from which they are derived. Observe microscope specimens of Chara. In the space below draw Chara, identifying the oogonium, antheridium and nodes. Show detail of structure.
Discuss the evolution of terrestrial plants from Charophyte ancestors. _____________________
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What is the function of the antheridium and the oogonium? _____________________________
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Explanation / Answer
1. There are a large number of facts which points towards the fact that Terrestrial plants evolved from Charophytes. Plants share a number of common traits with charophytes.
They include
(a) Rings of cellulose synthesizing protein in plasma membrane and these proteins synthesize cellulose microfibrils, which forms cell wall
(b) Peroxisomes of charophytes and plants contain enzymes which help in reducing the loss of organic products produced as a result of photorespiration.
(c)Some species of flagellated sperm producing plants sperm are similiar to those of charophytes
(d) Formation of Phragmoplast is common to both plants and charophytes
These morphological evidences along with evidences from genetic analysis indicate that charophytes are closest living relative of land plants
2. The male reproductive structure is called anthredium and the female reproductive structure is called oogonium. The anthredium produces sperms and oogonium produces eggs
The reproductive organs of the Charophytes include the female organ which is a oval structure with an envelope of spirally arranged, bright green filaments of cells, known as oogonium. The male organ is bright yellow or red in colour, spherical in shape, and is termed as antheridium. The oogonium is formed above the antheridium in many dioecious species. In others the monoecious condition is prevalent by the development of the antheridium before the formation of the oogonium, thus preventing fertilization by antherozoids of the same alga. In this scenario the two types of sex organs arise from different points on the lateral branches
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