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Reddening and regreening: The role of anthocyanin in water stressed leaves of a sclerophyllous shrub.
Evans, Danae*,1, Pratt, R.1, Davis, Stephen 1, 1 Pepperdine University, Malibu, California
ABSTRACT- Malosma laurina is a dominant species in chaparral shrub communities of Southern California. We observed reddening of leaves in this species during a severe drought in winter 2002 where rainfall was the lowest in recorded history. We hypothesized that severe water stress was contributing to increased anthocyanin production as a photo-protective mechanism for leaves. To test this hypothesis, we measured water potential (x), dark adapted leaf fluorescence (Fv/Fm), and recovery of fluorescence quantum yield (Fv'/Fm') after exposure to a 120 minute high light treatment (2200 mol m-2 s-1). Measurements were made under laboratory conditions and across three experimental treatments in the field over 8 months: red plants experiencing drought, green plants experiencing drought, and green irrigated plants as a control. Water potential of red and green plants under stress were not different (p = 0.11-0.75), but irrigated control plants were (p < 0.05). Dark adapted leaf fluorescence (Fv/Fm) at predawn and dusk was not different for red plants compared to green plants (p = 0.065-0.61). Exposure of leaves to 2200 mol m-2 s-1 for two hours caused a greater decline in Fv'/Fm' for red leaves compared to green leaves. Red leaves displayed slower recovery of Fv/Fm compared to green leaves. Red leaves in situ regreened after the onset of fall rains and demonstrated Fv/Fm recovery patterns similar to those of irrigated plants. Our findings suggest that leaves which turn red under water stress behave differently than red and green leaves of senescent plants as previously reported in the literature.
Key words: chaparral, anthocyanin, drought, Malosma