Plants: Anatomy, Growth and Function

1. Plants: Anatomy, Growth and Function 12.5: Transport in Vascular Plants

2. Overview of transport in plants • Water and minerals transported in phloem • Sugars transported in phloem

3. Transport of water and minerals • 3 stages in water and nutrient transport: from soil into roots, from roots to stem and from stem to leaves

4. Transport into roots • Happens by two processes: osmosis and active transport • Water enters plant root cells by osmosis • Nutrients enter plant cell from soil water by active transport http://www.revisionworld.com/country.php

5. Casparian strip • Casparianstrip is wax-like substance which prevents substances from leaking back into cortex. • Nutrients are actively transported into xylem once inside vascular cylinder. http://www.cartage.org.lb/en/themes/sciences/botanicalsciences/PlantHormones/PlantHormones/PlantHormones.htm

6. Transport into the stem • Xylem sap moves upwards by two processes: root pressure and capillary action

7. Transport into stem: Root pressure • Caused by build-up of water in xylem pushing on cells • Root pressure provides force to push water up stem • Not enough to transport water higher than about 3 m https://www.meted.ucar.edu/loginForm.php?urlPath=hydro/basic_int/hydrologic_cycle&go_back_to=http%253A%252F%252Fwww.meted.ucar.edu%252Fhydro%252Fbasic_int%252Fhydrologic_cycle%252Fimage_gallery.htm

8. Transport into stem: capillary action • Due to adhesive and cohesive forces • Xylem sap moves from one tube to another and also out of xylem into surrounding tissue

9. Transport to the leaves • Transpiration is process by which water evaporates through stomata of leaves. Main driving force of water up the plant. http://academic.kellogg.cc.mi.us/herbrandsonc/bio111/animations/0031.swf

10. Turgor • when plant lacks water, it will lose turgorand plant may wilt http://sun.menloschool.org/~dspence/biology/chapter6/chapt6_10.html

11. Transport of Sugars • Source is cell with high concentration of sugars. Sink is cell with low concentration of sugars. • Sugars can move up or down plant depending on season or stage of plant’s development http://scienceaid.co.uk/biology/plants/translocation.html

12. Movement of sugars: spring vs. summer • In spring, sugars move upwards from roots to upper portion of plant • In summer, sugars move downwards http://www.mhhe.com/biosci/esp/2001_gbio/folder_structure/pl/m4/s3/plm4s3_1.htm

13. Transport of sugars: phases • divided into three phases: transport of sugars from source cells to phloem cells, transport through the phloem, and transport from phloem cells to sink cells

14. Transport of sugars: source to phloem • Usually by active transport • In angiosperms, moves from source to sieve tube elements. In gymnosperms, from source into sieve cells. • as concentration of sugars in phloem cells increases, amount of water decreases. Water moves from xylem to phloem by osmosis increasing turgorof phloem cells near source cells http://www.ringwoodbiology.co.uk/transport.htm

15. Transport of sugars: Translocation • Translocation is long-distance transport of substances through phloem • Structure of phloem cells allows sugar to move quickly • may be caused by difference in turgor between phloem cells near source and phloem cells near sink http://plantcellbiology.masters.grkraj.org/html/Plant_Cellular_Physiology6-Translocation_Of_Organic_Solutes.htm

16. Transport of sugars: from phloem to sink • Happens by passive transport • In angiosperms, this happens from sieve tube elements to companion cells and then to sink cells. In gymnosperms, this happens directly from sieve cells to sink cells. • Water moves to xylem from phloem via osmosis. http://plantsinaction.science.uq.edu.au/edition1/?q=content/5-4-5-mechanism-phloem-translocation

17. VIDEO • http://www.youtube.com/watch?v=Zpu6Vm-9coM

18. 13.1 Succession • succession is gradual change in species composition within a community over time. • We will discuss two types: primary and secondary

19. Primary Succession • takes place on completely barren rock or mineral deposits normally created by volcanic eruptions, retreating glaciers or explosions. • First organisms to colonize are called pioneer species. http://cochranshalfacre.pbworks.com/w/page/30560637/5-Chukri,-Daniel-Primary-and-Secondary-succession

20. Secondary Succession • succession that occurs after existing community has been disturbed by natural events or by human activities • differs from primary succession because the land may contain some plants and organic matter within the soil http://mrswolfgang.wikispaces.com/Ecological+Succession+Monyak+Rodgers

21. Human Activity and Succession • human action can affect succession positively and negatively • humans disturb the natural process when they plant monocultures of grass in their yards or when they destroy non-grass species on their lawns • humans can positively affect succession by increasing biodiversity and stability in communities http://www.weareecofriendly.com/eco-friendly-herbicides/ http://www.journalism.ryerson.ca/websites/master/master.aspx?main=320&sub=111

22. 13.2 Asexual Reproduction in Seed Plants • Asexual reproduction is when single parent produces identical offspring (called vegetative reproduction • Grass species reproduce asexually by producing rhizomes, underground stems from which new plants arise. http://www.howstuffworks.com/grass.htm

23. Structures involved in asexual reproduction • different structures involved in different plants • Rhizomes such as corms and stolons, modified leaves, suckers, and fragments of roots or shoots http://hubpages.com/hub/How-to-Control-Plant-Suckers-and-Plant-Suckering-in-the-Garden http://plantpropagation.com/corms.htm

24. Benefits of Asexual Reproduction From textbook Offered by class • when environment is ideal for group of plants, they will all have ability to survive • takes less energy and less time • no reliance on other individual • plantlets formed by asexual reproduction are stronger than seedlings produced from sexual reproduction

25. Costs of Asexual Reproduction From textbook Offered by class • lack of variation in individuals means that if environment changes significantly, all individuals will be affected

26. Human uses of asexual plant reproduction • farmers, gardeners, and commercial nurseries use asexual reproduction to clone plants with desirable qualities rapidly and easily http://apps.cimmyt.org/english/docs/brochure/Apomixis/htm/apomixisbroch-engl.htm

27. Methods of asexual reproduction used by humans • Stem cuttings -placed in water, species quickly grow new roots at cut edge which can then be transferred to soil. http://gardeningdreaminspire.blogspot.com/2008/11/rooting-stem-cuttings-of-mints-purple.html

28. Methods of asexual reproduction used by humans 2) Grafting -young branch (scion) cut from plant with desirable traits and attached to stem of another plant (stock). -When successful, cambium of scion and stock grow together so their vascular tissues fuse. http://www.fao.org/docrep/03650e/03650e0e.htm

29. Methods of asexual reproduction used by humans 3) Tissue cultures -grow plant clones by placing piece of plant in series of culture media where plant tissue can grow into complete plant http://www.bio.davidson.edu/people/kabernd/seminar/2002/method/amy/aj.htm