A method to experimentally clamp leaf water content to defined values to assess its effects on apoplastic pH
Results
An experimental setup was developed where LWC is measured by a sensor based on IR-transmission and its signal processed to control a pump which circulates air from the cuvette through a cold trap. Hereby a feedback-loop is formed, which by adjusting vapour pressure deficit (VPD) and consequently leaf transpiration can precisely control LWC. This technique is demonstrated here in a combination with microscopic fluorescence imaging of apoplastic pH (pHapo) as indicated by the excitation ratio of the pH sensitive dye OregonGreen. Initial results indicate that pHapo of the adaxial epidermis of Vicia faba is linearly related to reductions in LWC.
Conclusions
Using this setup, constant LWC levels, step changes or ramps can be experimentally applied while simultaneously measuring physiological responses. The example experiments demonstrate that bringing LWC under experimental control in this way allows better controlled and more repeatable experiments to probe quantitative relationships between LWC and signaling and regulatory processes.
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