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Hornworts Domain Eukarya Kingdom Plantae Phylum Bryophyta.

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Presentation on theme: "Hornworts Domain Eukarya Kingdom Plantae Phylum Bryophyta."— Presentation transcript:

1 Hornworts Domain Eukarya Kingdom Plantae Phylum Bryophyta

2 Anthoceros: gametophyte thallus with elongating sporophyte Why is this called a hornwort?

3 Gametophyte Anthoceros - the hornwort The gametophyte is much like a thallose liverwort. The sporophyte is the horn of the hornwort.

4 Hornwort Thallus Cross Section photosynthetic upper epidermis cortex lower epidermis rhizoids

5 Compared to the liverwort thallus, what is missing?

6 Cyanobacteria are often symbionts!

7 What cellular details can you find?

8 The Anthoceros gametophyte thallus has one chloroplast per cell... Obviously like all other bryophtyes: chlorophylls a and b xanthophylls and carotenoids

9 Compared to the liverwort, what is different about the location of the antheridia in hornworts?

10 Antheridium sterile jacket Spermatogenic tissue Stalk

11 This Anthoceros gametophyte… Antheridium sterile jacket Spermatogenic tissue Lower Epidermis Rhizoids Thallus parenchyma Upper Epidermis shows three antheridia…

12 Here is the best I could find on the web to show the archegonium which is embedded in the hornwort gametophyte thallus. Apical Cell Sterile Jacket Cells Neck Canal Cells Ventral Canal Cell Egg Cell

13 The artist would lose one point above…why? What are some missing items as well? The spore mother cell is better known as sporocyte! We shall find out why this is so, as we proceed to more- derived plants.

14 sporangium stalk foot intercalary meristem gametophyte collar Hornwort sporophyte (with attached gametophyte)

15 Whole mount closeup What apomorphy is featured here?

16 Longitudinal section

17 The Anthoceros sporophyte foot is embedded in the gametophyte. The sporophyte seta has an intercalary meristem. Foot Intercalary Meristem Gametophyte Thallus Gametophyte rhizoids

18 The Anthoceros sporophyte has evolved guard cells and stomata. While initially dependent on the gametophyte, it carries out its own photosynthesis. The sporophyte may continue to grow while the gametophyte degenerates. Two apo- morphies are shown here… which?

19 What is this? How could it be labeled?

20 sterile jacket sporocyte The Anthoceros sporangium is linear and indeterminate in size. It is surrounded by a layer of cortex and epidermis. The sporocytes divide by meiosis, producing meiospores. The tri-radiate marks and surfaces that the tetrad of spores impress upon each other are shown here.

21 Hornwort sporangium ls

22 cs, ls, or wm?

23 What would be the labels on this?





28 The sporophyte shows a cutinized epidermis, a step up from the gametophyte. Spores appear in tetrads (the four meiotic products) of which three are generally in any plane of section In the center of the sporophyte, you can find the hydroids and leptoids! The cortex cells are responsible for the photosynthetic support for the sporophyte. Here is the cross section of a maturing part of the horn…the Anthoceros sporophyte.

29 The sporophyte maturing to shed spores to the wind

30 The Anthoceros sporophyte matures from tip to base shedding almost unlimited spores due to intercalary meristem at base.

31 The tip of the Anthoceros sporophyte matures first, shedding the spores to the wind.

32 SYNGAMY zygote SporophyteGametophyte sporangium sporocyte spores gametangia gametes germination mitosis differentiation mitosis germination mitosis 1N 2N differentiation MEIOSIS The Life Cycle of Anthoceros

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