Transpiration Adaptation Time Periods to Changing

Transpiration Adaptation Time Periods to Changing
Ambient CO2 Concentrations.
Leonid Asipov1
L-Data Research LTD,
Israel
Abstract
CO2 response curves are a common experimental procedure for assessing plants
photosynthetic and water consumption properties. The measurements are performed on a
leaf patch confined in a sealed chamber, with controlled temperature, illumination, humidity
and ambient CO2 concentration (Ca). The response curves are obtained from measurements
with stepwise increases in the Ca. In order to keep experiment uniformity and reduce the
measurement noise, the data sampling following every Ca alteration, has to take place after
the parameters have reached their steady state. However, in the existing literature we
have found no report suggesting the optimal time intervals sufficient for transpiration to
reach it. Few studies reported usage of coefficient-of-variation (COV) to determine the
steady-state point. The reported COV threshold was 2-5% per minute. In this study we’ve
verified whether the COV method is accurate for steady state determination, and have
estimated experimentally the optimal time intervals should be used for CO2 response curves
of Tomato and Arabidopsis plants. We’ve found a considerable difference between curves
with short (four to five minutes) and longer (25-40) constant time lags between the
sampled points, in both plants. Our conclusions are that using COV to determine steady
state of parameters can lead to inaccuracy especially in parameters with slow response,
such as the transpiration rate. The preferred strategy, keeping uniformity between different
experiments, is to define a constant adaptation time lag, for all the curves, which optimally
found to be 20-40 minutes for both, Arabidopsis and Tomato plants