Chlorophyll fluorescencein vivo as an indicator of water stress in potato leaves

Abstract

Potato plants, cv. Desiree, were exposed to a -0.3 MPa polyethylene glycol-induced water stress for 24 h in a hydroponic system. Leaves with a Leaf Plastochron Index of 3 to 3.99, 4 to 4.99 and 6 to 6.99 were measured for total, osmotic and pressure potential, leaf conductance andin vivo chlorophyll fluorescence transients Fo, Fp and FT. Leaf conductance and Fo significantly declined with leaf age in unstressed leaves. Water potential components and leaf conductance were significantly lower after 4 h of water stress whereas all three chlorophyll fluorescence transients measured after 24 h were significantly higher. The increase in fluorescence transients suggested that PSII electron acceptors were reduced faster than PSI and the Calvin cycle could oxidize them.In vivo chlorophyll fluorescence provides a greater understanding of the physiological effects of water stress but it requires additional experimentation to make it useful in screening for water stress tolerance.