The angiosperms

1. The angiosperms Greek: angeion case; sperma seed By far the most diverse group of plants that has ever existed with more than 240,000 different species.

2. Why are there so many species Angiosperms Time scale Origin of angiosperms Mosses Ferns Why are there so many species?

3. Gondwana Angiosperms probably originated in the tropics West Gondwana, equivalent to modern South America plus Africa Gondwanaland

4. Principal differences between Gymnosperms and Angiosperms 1. Leaves have finely divided venation 2. Xylem contains vessels as well as tracheids and parenchyma 3. Phloem contains sieve elements with companion cells 4. Ovules protected within an enclosed structure 5. Double fertilization to produce diploid zygote and triploid endosperm nucleus 6. Generally hermaphrodite flowers and cross pollinating (70%)

5. Monocotyledons and Dicotyledons Examples Grasses Triticum, wheat Zea mays corn lillies Oak trees, Quercus Coleus Lycopersicon, tomato Potato, Solanum tuberosum

6. Angio-Gymno 1. Leaves have finely divided venation Coleus leaf cleared of cell contents and with xylem stained A dicotyledon Typically veins are distributed such that mesophyll cells are close to is a vein. The network of veins also provides a supportive framework for the leaf.

7. Leaf of a monocotyledon plant The major venation follows the long axis of the leaf and there are numerous joining cross veins so that, as with the dicotyledon, mesophyll cells are always close to a vein.

8. Diagram of a dicot leaf

9. Tomato leaf Upper epidermis Pallisade parenchyma: chloroplasts visible around cell periphery Longitudinal section through a vascular bundle Xylem vessel: annular thickening around cell wall Phloem Bundle Sheath Spongy parenchyma Lower epidermis

10. Ficus leaf Ficus, the fig, is a xerophyte Collenchyma forming a hypodermis Pallisade parenchyma Spongy parenchyma Vascular bundle Collenchyma above and below the vascular bundle Lower epidermis

11. Leaf cross section of Bouteloua Upper epidermis Bulliform cells Collenchyma Xylem Parenchyma with chloroplasts Lower epidermis Bundle sheath cells with chloroplasts Phloem Sclerified fibers http://www.uri.edu/artsci/bio/plant_anatomy/99.html

12. … C3 and C4 photosynthesis?

13. Leaf cross section of Zea mays ("corn"). Upper epidermis Bulliform cells Xylem Bundle sheath cells with chloroplasts Parenchyma with chloroplasts Lower epidermis Phloem http://www.uri.edu/artsci/bio/plant_anatomy/99.html

14. Anatomical separation of the C4 photosynthesis component processes Parenchyma filled with chloroplasts Bundle sheath cells filled with chloroplasts. CALVIN REACTION SITE Xylem Phloem Carbon skeleton compounds return to parenchyma C4 acids synthesized in the parenchyma move to the bundle sheath

15. Ways in which Angiosperms are different from Gymnosperms Angio-Gymno 2. Xylem contains vessels as well as tracheids and parenchyma Angio-Gymno 3. Phloem contains sieve elements with companion cells

16. Angiosperm xylem and phloem In Angiosperms Xylem and Phloem contain more specialized cells than in Gymnosperms as well as containing Fibers and Parenchyma. Xylem: Vessel Elements Phloem: Sieve elements, Companion cells

17. Vessels Tracheids provide better support but less slower rates of water conduction than vessels Vessel Tracheid Wide vessel element: This kind of cell is better for fluid conduction than physical support. A vessel is composed of several vessel elements These vessel elements have completely perforated end walls Elongated vessel element: This cell provides moderate support and fluid conduction. Tracheids lack perforation plates but their end walls contain numerous pits.

18. Phloem Companion Cells (CC) Sieve Tube Members (STM) Cucurbita phloem (cucumber) Sieve plate STMs and CCs develop from the same progenitor cell. STMs, are columnar cells and unite vertically to form a Sieve Tube. STMs have no nucleus at maturity and depend on CC to regulate physiological processes. Each STM has one to several CC. The Sieve Plate is analogous to a Perforation Plate in vessels.

19. Dicotyledon stem cross section J. D. Mauseth Angelica stem transverse section is typical of a dicotyledon plant without secondary thickening. Stems as diverse as slender vines, fat cacti, or as modified as potato tubers all have this organization, but with various zones modified. Cacti are so wide because they have an exceptionally thick cortex. Potato tubers have a gigantic pith and almost no wood. Four zones: 1) epidermis 2) cortex, in many species the outermost part is a hypodermis 3) ring of vascular tissues, usually a ring of vascular bundles 4) pith. We eat Angelica in confectionary

20. Transverse section of corn stem, Zea mays. Transverse section of corn stem, Zea mays. This is the organization of monocot stems: numerous vascular bundles distributed throughout a tissue that may be either parenchyma or collenchyma Vascular bundles There are four parts: 1) epidermis 2) cortex with or without part differentiated into a hypodermis 3) vascular bundles 4) a matrix of parenchyma called conjunctive tissue or pith

22. Sections you need to have read 17.10, 31.2 through 31.6 Courses that deal with this topic Botany 443 Origins of our modern floras