Characteristics of Electrical Signals in Poplar and Responses in Photosynthesis

Author:

Lautner Silke1,Grams Thorsten Erhard Edgar1,Matyssek Rainer1,Fromm Jörg1

Affiliation:

1. Fachgebiet Angewandte Holzbiologie, Technische Universität München, 80797 Munich, Germany (S.L., J.F.); and Lehrstuhl Ökophysiologie der Pflanze, Technische Universität München, 85354 Freising, Germany (T.E.E.G., R.M.)

Abstract

Abstract To gain an understanding of the role of electrical signaling in trees, poplar (Populus trichocarpa, Populus tremula × P. tremuloides) shoots were stimulated by chilling as well as flaming. Two kinds of signal propagation were detected by microelectrode measurements (aphid technique) in the phloem of leaf veins: (1) basipetal, short-distance signaling that led to rapid membrane hyperpolarization caused by K+-efflux within the leaf lamina; and (2) acropetal, long-distance signaling that triggered depolarization of the membrane potential in the leaf phloem. In the latter, the depolarizing signals travel across the stem from the manipulated leaves to adjacent leaves where the net CO2 uptake rate is temporarily depressed toward compensation. With regard to photosystem II, both heat-induced long-distance and short-distance signaling were investigated using two-dimensional “imaging” analysis of chlorophyll fluorescence. Both types of signaling significantly reduced the quantum yield of electron transport through photosystem II. Imaging analysis revealed that the signal that causes yield reduction spreads through the leaf lamina. Coldblocking of the stem proved that the electrical signal transmission via the phloem becomes disrupted, causing the leaf gas exchange to remain unaffected. Calcium-deficient trees showed a marked contrast inasmuch as the amplitude of the electrical signal was distinctly reduced, concomitant with the absence of a significant response in leaf gas exchange upon flame wounding. In summary, the above results led us to conclude that calcium as well as potassium is involved in the propagation of phloem-transmitted electrical signals that evoke specific responses in the photosynthesis of leaves.

Publisher

Oxford University Press (OUP)

Subject

Plant Science,Genetics,Physiology

Reference53 articles.

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3. Bowles DJ (1990) Defense-related proteins in higher plants. Annu Rev Biochem59:873–907

4. Bulychev AA, Niyazova MM, Rubin AB (1987) Fluorescence changes of chloroplasts caused by the shifts of membrane-potential and their dependence on the redox state of the acceptor of photosystem-II. Biol Membr4:262–269

5. Bulychev AA, Niyazova MM, Turovetsky VB (1986) Electro-induced changes of chlorophyll fluorescence in individual intact chloroplasts. Biochim Biophys Acta850:218–225

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