Team

Stomatal control of transport processes at the plant leaf – atmosphere interface

Plants are significantly affecting the global climate by transpiring large amounts of water into the atmosphere. Water is a major constituent of natural green house gases. A better understanding of the coupling between vegetation and atmosphere is therefore needed, e.g. to improve global water balance models and for climate predictions.

We use tunable diode laser absorption spectroscopy (TDLAS) to probe absolute water concentrations directly at a living plant leaf. This technique has the necessary dynamic resolution from approximately 1ppm to at least 50000ppm water and a temporal resolution of below 0,1s for observation of fast biological responses.

Initially, we investigated the ratio between adaxial and abaxial transpiration under changing environmental conditions¹. An improved setup measured spatially resolved transpiration rates under a plant leaf during partial shading of its surface.

With a laser scanning technique and a 2,6µm tunable diode laser the concentration boundary layer beneath a plant leaf in a wind tunnel was probed². Using the results from these experiments we constructed a new setup for the simultaneous measurement of stomatal conductance, boundary layer conductance and transpiration rate for different sets of environmental conditions.

There are many ideas for a systematical investigation of the various interactions in this complex system. To further increase the spatial resolution of our measurements a 512-channel CCD IR sensor array could be implemented in a revised setup.

[1] S. Hunsmann, K. Wunderle, S. Wagner, U. Rascher, U. Schurr, V. Ebert: „High Resolution Measurements of Absolute Water Transpiration Rates from Plant Leaves via 1.37 µm Tunable Diode Laser Absorption Spectroscopy (TDLAS)”, Appl. Phys. B 92, 393-401 (2008).

[2] K. Wunderle, S. Wagner, I. Pasti, U. Rascher, U. Schurr, V. Ebert: "Distributed feedback diode laser spectrometer at 2.7 ?m for sensitive, spatially resolved H2O vapor detection", Appl. Opt. 48, B172-B182 (2009).