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

18. 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

19. 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

20. 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

21. 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

22. 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

23. Benefits of Asexual Reproduction From textbook Offered by class For agriculture purposes: farmers can quickly produce plant species for less time and money More consistent growth and higher survival rate of offspring Genetic engineering of identical plants for medical purposes Could decrease time over which succession occurs • 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

24. Costs of Asexual Reproduction From textbook Offered by class Same type of plant requires same type of nutrients from soil so could lead to deficiencies in that area No chance of evolution taking place Any negative trait will be passed down to all offspring More competition for resources such as light, nutrients, soil • lack of variation in individuals means that if environment changes significantly, all individuals will be affected

25. 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

26. 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

27. 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

28. 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