1. Feb. 15 th, 2011 B4730/5730 Plant Physiological Ecology Whole Plant Carbon Balance I

3. Phaseolus vulgaris; Tcherkez et al Pl Phys. 2003

4. Hymus et al New Phyt. 2005

5. (Ehleringer et al., 1991).

6. Water Sources and Water Isotopes (Dawson and Ehleringer, 1991).

7. Gas Exchange Gas exchange of whole plant passes through stomatal and nonstomatal surfaces –Bark, lenticels –Cuticles Conductances summed in series and parallel Stomates are one of the most active physiological response plants have to environment

8. Derivation of Stomatal Conductance Stomatal conductance = g s =D j na st /(δ st + r st ) –m s -1 (usually mm s -1 ) –Easiest measurement from water exchange Molecular diffusion coefficient = D j –m 2 s -1 –(2.4 x 10 -5 ) for water at STP Ratio of stomata area to leaf area = na st –Unitless –0.02 mesic example Depth of stomatal pore = δ st –m –20 x 10 -6 m mesic example Radius of stomata r st –m –5 x 10 -6 m mesic example

9. Conversion of Stomatal Conductance Units Units of m s -1 are mostly used by meteorologist, physiologist and ecologist like mol m-2 s-1 Conversion to mol m -2 s -1 uses ideal gas law –Equations in front of book, account for Pressure and Temperature change Stomatal parameters –Stomatal Density (# mm -2 ) –Stomatal Index (stomatal area/epidermal area) –Index is less sensitive to CO 2 levels than density

10. Arabidopsis thaliana; Torii Plant Cell Mongraphs 2007

11. Water Use Efficiency Water use efficiency is the ratio of CO 2 uptake to H 2 O loss –WUE = A/E = C a (1-(C i /C a ))/1.6VPD –VPD effect often neglected –Be careful of ratio effects Water use efficiency increases with water stress and light –A vs. E L at different light levels –g s vs. A changes with plant functional types –Ci/Ca is related to water use efficiency (intrinsic) – 18 O may help with relative A to g s contribution

12. Rajabi 2006 in Seibt et al Oecol. 2008

13. Pinus pinaster; Ogee et al PCE 2010

14. Fagus sylvatica; Ferrio et al PCE 2009

15. 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

16. 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

17. Van Bel PCE 2003

20. Münch Pressure Flow Sevanto et al. PCE 2003