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Feb. 17 th , 2011 B4730/5730 Plant Physiological Ecology

Feb. 17 th , 2011 B4730/5730 Plant Physiological Ecology. Whole Plant Carbon Balance II. Fagus sylvatica; Ferrio et al PCE 2009. Phloem Properties. Sieve elements retain minimal metabolic function to facilitate transport Increasing loss of metabolic function with evolution No nucleus

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Feb. 17 th , 2011 B4730/5730 Plant Physiological Ecology

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  1. Feb. 17th, 2011B4730/5730Plant Physiological Ecology Whole Plant Carbon Balance II

  2. Fagus sylvatica; Ferrio et al PCE 2009

  3. Phloem Properties • Sieve elements retain minimal metabolic function to facilitate transport • Increasing loss of metabolic function with evolution • No nucleus • Surrounding parenchyma have increased metabolic function • Companion cells in angiosperms • Rapid plugging of wounded sieve elements precluded functional studies until recently • Phloem specific protein

  4. Sources and Sinks • Munch hypothesis that osmotic forces drive sugar transport • Active loading of phloem at sources • Moves water from xylem to phloem • Active unloading of phloem at sinks • Moves water from phloem to xylem • Pressure gradient maintained between sources and sinks • Environmental controls largely unknown • Sugar signals • mRNA transport • Girdling studies • pressure waves and osmotica

  5. Van Bel PCE 2003

  6. Münch Pressure Flow Sevanto et al. PCE 2003

  7. Sevanto et al. PCE 2003

  8. Signaling and Phloem Flow • Carbohydrate source/sinks control photosynthesis • Lack of sink causes buildup and feedback inhibition of A; starch granules • symplastic vs apoplastic phloem loading • Hormones and RNA provide direct signals • Type of RNA and exact mechanisms not fully understood • Many studies document time lags between photosynthesis and respiration -isotopic vs time lag evidence

  9. Tournier et al Pl. J. 06

  10. Pinus taeda; Johnsen et al PCE 2007

  11. Iglesias et al Phys Plant 02 Citrus unshiu

  12. Mencuccini & Holta; New Phyt 2010

  13. grassland; Bahn et al New Phyt 2009

  14. Gough et al Biosci 2008

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