Chlorophyll fluorescence lifetime determination of waterstressed C3- and C4-plants

This article describes the effect of water stress on the room temperature chlorophyll fluorescence lifetime of plants of wheat (C3) and maize (C4). In addition, net CO₂ assimilation rate (P_N), stomatal conductance and the fluorescence quenching coefficients qP and qNP at steady state conditions were recorded. The overall fluorescence decay of the control plants can be described by an average decay time of 1 ns for both plant types. Water stress did not modify this parameter in the case of wheat, whereas a shortening of the decay was observed for waterstressed maize plants (τ=0.45 ns). This shortening in the chlorophyll fluorescence decay was accompanied by an increase in the nonphotochemical quenching (qNP). The photochemical quenching (qP) and therefore the electron transport via photosystem II remains unaffected by water stress. The most pronounced effect of the stress for both plant types was a decrease in P_N due to a closure of the stomata.