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#Green Algae

13 public questions tagged with this topic.

Plant Classification

Which feature is absent in Charophyte algae?

Charophytes anticipate many land plant cytological features such as phragmoplast microtubule array, plasmodesmata in some groups with incomplete cell wall separation, branching mucilaginous thallus, and oogamous reproduction with flagellated sperm, but lack true alternation of generations with multicellular diploid sporophyte dependent on gametophyte producing walled spores inside sporangia. They exhibit haplontic cycle where zygote undergoes meiosis directly producing haploid cells. Charophytes possess cellulose walls, chlorophyll a and b, starch. Absence of embryophytic alternation distinguishes them from land plants which evolved sporophyte elaboration after terrestrial colonization.

Ref: Graham & Wilcox 2000 Charophyte evolution; Becker & Marin 2009; Campbell Ch 29

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Plant Classification

The storage product common to plants and green algae is

Carbon storage biochemistry reflects evolutionary divergence among major algal lineages. Green plants including charophytes and embryophytes polymerize photosynthetic glucose into alpha 1-4 amylose and branched amylopectin starch grains housed within plastids surrounded by double membrane and often thylakoids, stain blue-black with iodine solution. In contrast, red algae store floridean starch in cytosol, brown algae store laminarin beta glucan, euglenoids store paramylon, animals and fungi store highly branched glycogen. Starch storage inside plastid represents shared derived innovation supporting monophyly of Viridiplantae and adaptation to terrestrial life.

Ref: Graham et al. 2009 Starch storage; Campbell Biology Ch 10; Raven Algal Biology

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Plant Classification

Which pigment combination is common to plants and green algae?

Photosynthetic pigment composition provides important chemotaxonomic marker clarifying green plant evolution. Land plants and charophyte green algae contain chlorophyll a as primary reaction center pigment plus accessory chlorophyll b broadening absorption peaks in blue and red spectrum, with carotenoids beta-carotene, lutein and other xanthophylls for photoprotection. This specific combination housed in chloroplasts with grana stacks distinguishes Viridiplantae from Rhodophyta possessing chlorophyll a and phycobilins, Phaeophyta and diatoms with chlorophyll a and c plus fucoxanthin. Retention of chlorophyll a plus b supports close kinship.

Ref: Campbell Biology 12th Ch 28: Photosynthetic pigments; Raven Ch 7 Plastids

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