1 / 14

Spodnje veje zaradi zasenčenja manj fotosintetizirajo in zaradi pomanjkanja hrane odmirajo .

Spodnje veje zaradi zasenčenja manj fotosintetizirajo in zaradi pomanjkanja hrane odmirajo. GRČA = del veje v deblu. IGLAVCI v spodnjem delu veje nabira smola, zato se veja ne odlomi tik ob deblu , temveč na določeni razdalji od debla (10-20 cm). Deblo nato tudi

eyad
Download Presentation

Spodnje veje zaradi zasenčenja manj fotosintetizirajo in zaradi pomanjkanja hrane odmirajo .

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Spodnje veje zaradi zasenčenja manjfotosintetizirajo in zaradi pomanjkanja hrane odmirajo. GRČA = del veje v deblu. IGLAVCI v spodnjem delu veje nabira smola, zato se veja ne odlomi tik ob deblu, temveč na določeni razdalji od debla (10-20 cm). Deblo nato tudi desetletja obrašča mrtvi štrcelj, kar povzroči nastanek neželene izpadne grče. LISTAVCI v fazi odmiranja veje tik ob deblu nastane pribl. do 5mm debela zaščitna plast (začepljenje s tilami in gumoznimi snovmi), ki zaščiti odlomljeno mesto pred vdorom zraka in infekcijo. VRASLA SLEPICA veja se odlomi tik ob deblu – deblo jo preraste,

  2. GRČE ŽIVA VEJA – kambij in prirastne plasti veje prehajajo v debelni kambij in debelne prirastne plasti. Dokler je veja živa, so njena tkiva zrasla s tkivom debla - »zrasla« grča. VEJA ODMRE – povezava se prekine. Po odmrtju veje, pa jo deblo le obrašča in je tujek v deblu – »izpadna« grča. VRASLA SLEPICA –veja se odlomi tik ob deblu; deblo preraste ostanek veje. NA R PREREZU – KONIČASTA OBLIKA

  3. KITAJSKI BRKI PRI BUKVI IZPADNA GRČA ZRASLA GRČA SLEPICA Pri listavcihostanek zaščitne plasti, ki označuje mesto (naravnega) odloma veje. Na površini debla jo na nakazujejo »kitajski brki«-skorjina guba v pazduhi nekdanje veje- z »žigom« ali »bradavico v sredini pod njimi. Iz naklona brk je mogoče sklepati na globino slepice iz velikosti žiga pa na debelino odpadle veje. NA T PREREZU – OKROGLA-OVALNA OBLIKA UPORABNOST GRČAVEGA LESA?

  4. Kitajski brki pri bukvi.

  5. Knots • Knots are simply branches that the tree has either grown over or grown around. • trees grow outward as well as upward. When they get bigger around, the tree has to grow either around or completely over a branch. The overgrown branch becomes the knot! • Take a look at the picture on the right. Can you see that when this piece of wood was part of a tree it had a branch growing out where the knot is? You can click on the picture to take a closer look. • Knots make whole pieces of wood weaker. So, wood with knots usually isn't as valuable! It's important to know how knots effect the properties of wood when making wood products. We will learn more about wood products in a later lesson.

  6. http://www.woodmagic.vt.edu/html/Activities/rs3.htmhttp://forest.mtu.edu/research/hwbuck/hardwood_defects/rot.htmlhttp://www.woodmagic.vt.edu/html/Activities/rs3.htmhttp://forest.mtu.edu/research/hwbuck/hardwood_defects/rot.html • Knots can affect wood's strength. • If you want very strong wood, look for wood without knots. Knots significantly reduce wood strength.This doesn't mean that wood with knots is very weak -- knots just reduce the strength. • Knots reduce strength because they are a change in the direction of wood growth. When wood grows normally, all the cells grow in the same direction, but a know has cells that grow in a different direction. Knots interrupt the cells, so the cells become weaker!

  7. So prostori v lesu (iglavci) napolnjeni s smolo. SMOLIKE -manjša vrednost lesa -manjša trdnost lesa -manjša estetska vrednost

  8. so napetosti, ki se med rastjo vgrajujejo v les. rastne napetosti Periferija debla je v vzdolžni smeri vselej obremenjena na nateg in sredica na tlak Pri razžagovanju se notranje napetosti sproščajo in povzročajo veženje in pokanje lesa (sločenje v obliki loka ali sablje, nastanek srčnih razpok! Za razliko od sušilnih napetosti, se rastne napetosti in veženje/pokanje kažejo pri svežem lesu, tj. pri vlažnosti nad UTNCS!

  9. Porazdelitev rastnih napetosti v aksialni smeri pri tankem in debelem deblu. Deformacija radialne deske v obliki »sablje« ter tangencialne deske v obliki »loka« pri razžagovanju zaradi sproščanja rastnih napetosti.

  10. -po razžagovanju se notranje napetosti sprostijo -zunanje letve se skrajšajo in usločijo navzven

  11. www.dlib.si/v2/StreamFile.aspx?URN=URN:NBN:SI:doc...id..

  12. http://www.biomatnet.org/secure/Fair/S815.htm

  13. http://www.fathom.com/course/21701736/session3.html RASTNE NAPETOSTI

More Related