Chapter 29: Plant Diversity I: How Plants Colonized Land

1. Chapter 29:Plant Diversity I:How PlantsColonized Land

2. Overview of Plant Phylogeny Chamber-contained seed Chara, the outlier to the plant phylogeny, is a green alga Naked seed

3. More Detail Don’t worry about dates

4. Nonvascular Plants Nonvascular plants also lack woody tissue, seeds, flowers, and fruits Note majority are mosses

5. Seedless plants also lack flowers and fruits Vascular Plants Not all seed plants have flowers and fruits

6. Similarities in peroxisomes, flagellated sperm, and cell division also link charophyscean algae with green plants. Cellulose-Synthesis “These distinctly rose-shaped arrays of proteins are found only in land plants and charophycean algae, suggesting their close kinship.” p. 574, Campbell & Reece (2005)

7. From Alga to Plants

8. Charaphycena Algae

9. The ancestor of all plants was a green alga • Green algae have plant-like chloroplasts, plant-like cell walls, and a plant-like energy storage molecule (starch)… etc. • The ancestor of plants probably was a green alga that lived whole or partially in very shallow water, perhaps susceptible to periodic drying up • Those algae that could continue to metabolize despite not being completely covered with water presumably possessed a selective advantage—including shading those algae restricted to water • The first roots were stems (stipes) that physically connected out-of-water portions of algae with still-in-water portions • Water diffused through short stems to keep above-water, actively photosynthesizing tissues from desiccating Scenario for Algae to Plants

10. Algae: • Get minerals and water from surrounding water • Have their bodies supported by surrounding water • Their sperm and spores swim through the water • Plants: • Get their Minerals and Water from soil • Soil is subject to desiccation • Soil also is opaque to sunlight • Do not have their weight supported by surrounding water • Do not have, or have less water for sperm and spores to swim through • To survive on land, plant ancestors had to address these challenges The Challenges of Land

11. Waxy cuticles: water proofing of plant body • Stomata: holes in waxy cuticle • Sporophyte (alternation of generations): increased productivity per fertilization (does not exist in Charophycean algae) • Vascular tissue: connects roots to leaves • Woody tissue: allows greater plant height • Sporopollenin: polymer which prevents zygotes from drying out • Pollen: non-motile sperm carrier; also male gametophyte • Seeds: “…embryo packaged with a supply of nutrients inside a protective coat.” p. 579, Campbell & Reece (2005) • Flowers: allows more efficient pollen transfer • Fruit: embryo protection and dissemination Plant Innovations

12. Waxy Cuticle & Water Proofing Air is desiccating (unless humidity is 100%)

13. Stomate & Gas Exchange

14. Sporophytes,  Dominance Note: Plants are heteromorphic

15. Water and minerals are passed up the xylem, ultimately to be transpired out of the plant Vasculature (etc.) Sugar, amino acids, and other organic molecules are passed down phloem to the stem and roots

16. Cellulose  Cell Walls The cellulose of cell walls is important for supporting plant tissues against gravity’s pull

17. Lignin is the polymer that gives woody plants their woodiness Lignin  Woody Tissue Vasculature allong with woody tissue allowed plants to grow taller, so as to avoid being shaded by other plants

18. Coal  Anaerobic Decay

19. Gametangia Antheridium Oogonium Chara: No Sporophyte Zygote Essentially four spores per fertilization (corresponding to the typically 4 meiotic products)

20. Development of the sporophyte prior to meiosis Diploid parent (Sporophyte) Meiosis (delayed) Diploid zygote Haploid Spores Sperm (gamete) Egg ( gamete) Haploid parent (Gametophyte) Delaying Meiosis

21. Alternation of Generations

22. Diploid phase Syngamy Meiosis Gametes Spores Haploid phase A of G, Simplified!

23. Defining Plant Derived Traits Hence plants are described as embryophytes

24. Embryo Retention (Analogy) We’ve seen embryo retention before… But in plants the embryo is dependent on parent for nutrients

25. Defining Plant Derived Traits An apical meristem is the cell division that takes place at the tips of stems and roots

26. Bryophytes have flagellated sperm and disseminate using spores (not pollen) Bryophytes We will mostly concern ourselves with phylum Bryophyta

27. Liverworts Longer-lived (conspicuous) gametophyte

28. Hornworts Longer-lived (conspicuous) gametophyte

29. Mosses Longer-lived (conspicuous) gametophyte

30. Bryophyte Life Cycle

31. Mosses Life Cycle (in order L-R)

32. Seedless Vascular Plants We will mostly concern ourselves with phylum Pterophyta

33. Fern Sporophytes Longer-lived and larger (conspicuous) sporophyte

34. Fern Sorus

35. Fern Sporangium

36. Sporangium Releasing Spores

37. Germinating Fern Spore

38. Fern Gametophytes

39. Fern Gametangia

40. Young Fern Sporophytes

41. Fern Life Cycle

42. Evolution of Leaves

43. Innovation: Different Spore Types Seen in most non-seed bearing plants Seen mostly in seed bearing plants

44. When “Ferns” ruled the Earth! “Artists conception of a Carboniferous forest based on fossil evidence. Most of the large trees with straight trunks are lycophytes. The tree on the left with feathery branches is a horsetail. Tree ferns, not shown, here, were also abundant in the ‘coal forests’ of the Carboniferous.” p. 574, Campbell & Reece (2005)

45. The End