Light and Plant Development

H. Smith

• Publisher: Butterworth-Heinemann
• Year: 2013
• ISBN:
  9781483192536
• Topic: Biowissenschaften
• Subtopic: Physiologie

Light and Plant Development presents the Proceedings of the 22nd University of Nottingham Easter School in Agricultural Science. It discusses the spectral sensitivity of inhibition of flowering by light. It addresses the action spectrum for leaf enlargement and stem growth inhibition. Some of the topics covered in the book are the nature of the blue light photoreceptor in higher plants and fungi; re-examination of photochemical properties and absorption characteristics of phytochrome using high-molecular-weight preparations; and intermediates in the photoconversion of phytochrome. The high irradiance reaction is fully covered. The physiological evidence and localised responses, intracellular localisation and action of phytochrome are discussed in detail. The text describes in depth the immunological visualisation of phytochrome. The fractionation procedures and terminology are presented completely. A chapter is devoted to the photocontrol of enzyme levels. Another section focuses on the ribosomal RNA synthesis in developing leaves. The book can provide useful information to botanists, chemists, students, and researchers.

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H.A. BORTHWICK AND S.B. HENDRICKS – PIONEERS OF PHOTOMORPHOGENESIS¹

WINSLOW R. BRIGGS, Department of Plant Biology, Carnegie Institution of Washington, Stanford, California 94305, U.S.A.

Publisher Summary

This chapter lists some of the major accomplishments of H.A. Borthwick and S.B. Hendricks in the field of photomorphogenesis. In 1946, in one of the studies with Parker, they carefully examined the spectral sensitivity of inhibition of flowering by a light break in the middle of the night in two short-day plants, which were Biloxi soybean and cocklebur. Two years later came an action spectrum for night interruption in Wintex barley, which showed for the first time flowering promotion in a long-day plant under non-inductive photoperiod. In the next year, H.A. Borthwick and S.B. Hendricks were joined by F.W. Went to measure the action spectrum for leaf enlargement and stem growth inhibition in dark-grown pea seedlings. They, thus, obtained the first of many by now familiar action spectra for vegetative responses to phytochrome phototransformation. A year later, appeared another study of Parker, Hendricks and Borthwick on a long-day plant, Hyoscyamus. They then turned their attention to light-promoted lettuce seed germination, a system first discovered by Flint and McAlister in the mid-1930s at the Smithsonian Institution.

The participants in this 22nd Easter School take great pleasure in dedicating this volume to Dr Harry A. Borthwick and Dr Sterling B. Hendricks in honour of their monumental contributions to the field to which this School is devoted. Their early interest in flowering led them into a remarkable series of studies, the results of which are fundamental to most of what is discussed in this volume. Their research was carried out at the Pioneering Laboratory of Plant Physiology at the Plant Industry Station of the United States Department of Agriculture; they and their many colleagues made it one of the most distinguished laboratories in the world, and unique in the Department of Agriculture.

While it is not the purpose of these short paragraphs to review all of their work, it is appropriate to list some of their major accomplishments in photomorphogenesis. In 1946, in one of a series of studies with Parker, they carefully examined the spectral sensitivity of inhibition of flowering by a light break in the middle of the night in the two short-day plants Biloxi soybean and cocklebur (Parker et al., 1946). The results were the first action spectrum for a phytochrome effect, and showed an action maximum near 665 nm. Two years later came an action spectrum for night interruption in Wintex barley, showing for the first time flowering promotion in a long-day plant under non-inductive photoperiod (Borthwick, Hendricks and Parker, 1948). The action spectrum was essentially identical with that for the short-day plants, and constituted the first evidence that the same photoreceptor might regulate flowering in both types of photoperiodically sensitive plants. The next year (Parker et al., 1949) they were joined by F.W. Went to measure the action spectrum for leaf enlargement and stem growth inhibition in dark-grown pea seedlings. They thus obtained the first of many by now familiar action spectra for vegetative responses to phytochrome phototransformation. A year later (Parker, Hendricks and Borthwick, 1950) appeared another study on a long-day plant, Hyoscyamus. The work was really a condensed version of the Wintex barley paper, but it is significant in that the authors suggest for the first time a phycocyanin-like pigment as the photoreceptor - a full 15 years before the suggestion was verified experimentally.

They then turned their attention to light-promoted lettuce seed germination (Borthwick et al., 1952), a system first discovered by Flint and McAlister in the mid 1930s at the Smithsonian Institution. An action spectrum for promotion of germination showed a maximum at 665 nm, suggesting the same photoreceptor to be involved. However, since the lettuce seed system was known to be reversible by far-red light, they also obtained the first action spectrum for far-red reversal. The same paper reported repeated photoreversibility following several sequential alternating red and far-red treatments, and the authors proposed for the first time a single photoreversible pigment. A second paper on lettuce seed germination (Borthwick et al., 1954) explored the system in greater detail, demonstrating that the light reactions in both directions were independent of temperature, and showing for the first time escape from photoreversibility with time after far-red but not after red treatment.

Meanwhile, Borthwick, Hendricks and Parker (1952) asked the suddenly obvious question: since the action spectrum for promotion of lettuce seed germination was identical with those measured for the other effects, could these other effects be reversed by far-red light as well? Using cocklebur seedlings grown under day lengths that were sufficiently short for flowering, they showed that far-red light completely cancelled the effect of red light in inhibiting flower formation. The action spectrum for this far-red reversibility was roughly the same as that for lettuce seed germination. Photoreversibility was thus not just a peculiar property of certain varieties of lettuce seeds.

Other workers at Beltsville then demonstrated similar photoreversible control of flavone formation in tomato skins (Piringer and Heinze, 1954) and promotion of leaf enlargement and epicotyl elongation and inhibition of hypocotyl elongation in bean seedlings (Downs, 1955). Then Hendricks, Borthwick and Downs (1956) showed both with Pinto bean internodal elongation and Lepidium and lettuce seed germination that the photochemistry followed first-order kinetics for both red and far-red photoresponses. By this time, the Beltsville group was convinced that a single photoreversible pigment was involved, and they set out to find it.

Their success in detecting phytochrome spectrophotometrically in plant tissue and achieving preliminary isolation in buffer is documented in their often cited 1959 paper (Butler et al., 1959), a paper that marked the beginning of in vitro work with phytochrome. It also presented instrumentation techniques which are now widely used, not only for phytochrome but also for a wide variety of other types of spectral studies. There followed from Beltsville the first action spectrum for phytochrome phototransformation in vitro (Butler, Siegelman and Hendricks, 1964), the first partial purification technique for phytochrome (Siegelman and Firer, 1964), establishment of the chromophore as a bilitriene similar to allophycocyanin (Siegelman and Hendricks, 1965; Siegelman, Turner and Hendricks, 1966), and numerous other papers on phytochrome reactions both in vivo and in vitro. The demonstration (Fondeville, Borthwick and Hendricks, 1966) that leaflet closing in Mimosa was under rapid phytochrome control gave strong impetus to the already existing suspicion that phytochrome was somehow acting in association with a membrane system. This evidence, summarised by Hendricks and Borthwick (1967), was integrated into a useful model for phytochrome action (Borthwick et al., 1969).

Borthwick retained an active interest in phytochrome (Borthwick, 1972a,b) until his death on May 21st, 1974. Hendricks continues a vigorous pursuit of the problem of seed germination (Hendricks and Taylorson, 1975), where new ground is again being broken.

Among other things, what emerges from this listing of contributions is the extraordinary breadth of inquiry that Borthwick and Hendricks applied to plant photomorphogenesis. Their approaches ranged from whole plant physiology through organ physiology, biochemistry, photochemistry and biophysics. We commend them for this breadth, and for the durability, magnitude and insight of their research.

References

BORTHWICK, H. A.MITRAKOS K., SHROPSHIRE W., eds. Phytochrome. Academic Press: New York, 1972:3.

BORTHWICK, H. A.MITRAKOS K., SHROPSHIRE W., eds. Phytochrome. Academic Press: New York, 1972:27.

BORTHWICK, H. A., HENDRICKS, S. B., PARKER, M. W. Bot. Gaz. 1948; 110:103.

BORTHWICK, H. A., HENDRICKS, S. B., PARKER, M. W. Proc. Nat. Acad. Sci. U.S.A. 1952; 38:929.

BORTHWICK, H. A., HENDR...