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The diel cycle of Serianthes nelsonii leaflet movements was characterized under four levels of shade from full sun to 22% sunlight transmission to determine the photoprotective components of diurnal leaflet movements and the relationship to patterns of nocturnal leaflet movements. Treatments also included negating paraheliotropism by re-orienting plants every 15min throughout the photoperiod such that the plants never experienced a predictable solar vector. The timing of leaflet closure to avoid high light, the shape of the diurnal curve depicting leaflet angle, and the maximum extent of leaflet closure were influenced by the shade treatments. Protection of leaf function by paraheliotropism was also influenced by shade treatment, with the full sun plants exhibiting the greatest level of protection. Leaflet heat gain was reduced 50% by leaflet movement as determined by direct measurements of leaf-to-air temperature differences. Midday quantum efficiency of photosystem II was increased 120% by leaflet movement as determined by direct measurements of pulse modulated chlorophyll fluorescence. The extent of nyctinastic leaflet closure was greatest in the high light plants that moved the most midday and least in the shaded plants that moved the least midday, indicating the extent of diurnal paraheliotropism controlled the amplitude of nocturnal leaflet movement. Serianthes nelsonii is highly skilled at using movement to reduce leaflet exposure to the solar vector, providing instantaneous behavioral control over heat gain and photoinhibition. This case study of an endemic tree species in Micronesia has added to the nascent field of conservation physiology, and indicated that heliotropism of S. nelsonii leaves may provide the species with the ability to minimize high light damage during increased temperatures associated with climate change.
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Barlow, P.W. (2015). Leaf movements and their relationship with the lunisolar gravitational force. Annals of Botany 116: 149â€“187.
Berry, J., & O. Bjorkman (1980). Photosynthetic response and adaptation to temperature in higher plants. Annual Review of Plant Physiology 31: 491â€“543.
Cooke, S.J., L. Sack, C.E. Franklin, A.P. Farrell, J. Beardall, M. Wikelski & S.L. Chown (2013). What is conservation physiology? Perspectives on an increasÂingly integrated and essential science. Conservation Physiology 1(1): 1â€“23. https://doi.org/10.1093/conphys/cot001 DOI: https://doi.org/10.1093/conphys/cot001
Dodd, A.N., N. Salathia, A. Hall, E. Kevei, R. Toth, F. Nagy, J.M. Hibberd, A.J. Millar & A.A. Webb (2005). Plant circadian clocks increase photosynthesis, growth, survival, and competitive advantage. Science 309: 630â€“633.
dos Santos, A., L. Rosa, L. Franke & C. Nabinger (2006). Heliotropism and water availability effects on flowering dynamics and seed production in Macroptilium lathyroides. Revista Brasileira de Sementes 28: 45â€“52.
Ehleringer, J. & I. Forseth (1980). Solar tracking by plants. Science 210: 1094â€“1098.
Eisenstein, E.M., D. Eisenstein, & J.C. Smith (2001). The evolutionary significance of habituation and sensitization across phylogeny: a behavioral homeostasis model. Integrative Physiological & Behavioral Science 36: 251â€“265.
Forseth, I.N. (1990). Function of leaf movements. pp. 238-261. In: Satter, R.L., H.L. Gorton & T.C. Vogelmann (eds.). The Pulvinus: Motor Organ for Leaf Movement. American Society of Plant Physiology. Rockville, MD, U.S.A, 264pp.
Forseth, I.N. & J.R. Ehleringer (1983). Ecophysiology of two solar tracking desert winter annuals. III. Gas exchange responses to light, CO2 and VPD in relation to long-term drought. Oecologia 57: 344â€“351.
Fu, Q.A. & J.R. Ehleringer (1989). Heliotropic leaf movements in common beans controlled by air temperature. Plant Physiology 91: 1162â€“1167.
Gagliano, M., M. Renton, M. Depczynski, & S. Mancuso (2014). Experience teaches plants to learn faster and forget slower in environments where it matters. Oecologia 175: 63â€“72.
Genty, B., J.M. Briantais, & N.R. Baker (1989). The relationship between the quantum yield of photosynthetic electron-transport and quenching of chlorophyll fluorescence. Biochimica et Biophysica Acta 990: 87â€“92.
Genty, B., Y. Goulas, B. Dimon, G. Peltier, J.M. Briantais, & I. Moya (1992). Modulation of efficiency of primary conversion in leaves, mechanisms involved at PS2, pp. 603â€“610. In: Murata, N. (ed.). Research in photosynthesis, Vol. IV: Proceedings of IXth International Congress on Photosynthesis. Nagoya, Japan, 793pp.
Gorton, H.L. & R.L. Satter (1983). Circadian rhythmicity in leaf pulvini. BioScience 33: 451â€“457.
Kao, W.-Y. & I.N. Forseth (1992). Responses of gas exchange and phototropic leaf orientation in soybean to soil water availability, leaf water potential, air temperature, and photosynthetic photon flux. Environmental Experimental Botany 32: 153â€“161.
Mooney, H.A. & J.R. Ehleringer (1978). The carbon gain benefits of solar tracking in a desert annual. Plant Cell Environ. 1: 307â€“311.
Murchie, E.H. & T. Lawson (2013). Chlorophyll fluorescence analysis: a guide to good practice and understanding some new applications. Journal of Experimental Botany 64: 3983â€“3998.
Nilsen, E.T. & I N. Forseth (2018). The role of leaf movements for optimizing photosynthesis in relation to environmental variation. pp.401â€“423. In: Adams III, W. & Terashima, I. (eds.). The Leaf: A Platform for Performing Photosynthesis. Advances in Photosynthesis and Respiration, Vol. 44. Springer, Cham, 575pp.
Ueda, M. & Y. Nakamura (2007). Chemical basis of plant leaf movement. Plant & Cell Physiology 48: 900â€“907.
USFWS (1987). Endangered and threatened wildlife and plants; determination of endangered status for Serianthes nelsonii Merr. (Hayun Lagu or Tronkon Guafi). United States Fish and Wildlife Service Federal Register 52(32): 4907â€“4910. (Including correction of tabular error: Federal Register 52(42): 6651.)
USFWS (1994). Recovery plan for Serianthes nelsonii. United States Fish and Wildlife Service, Portland, Oregon.
van Zanten, M., T.L. Pons, J.A.M. Janssen, L.A.C.J. Voesenek & A.J.M. Peeters (2010). On the relevance and control of leaf angle. Critical Reviews Plant Science 29: 300â€“316.
Wikelski, M. & S.J. Cooke (2006). Conservation physiology. Trends in Ecology and Evolution 21: 38â€“46.
Wiles, G. & E. Williams (2017). Serianthes nelsonii. The IUCN Red List of Threatened Species: e.T30437A98715973. Accessed 5 May 2019. https://doi.org/10.2305/IUCN.UK.2017-3.RLTS.T30437A98715973.en DOI: https://doi.org/10.2305/IUCN.UK.2017-3.RLTS.T30437A98715973.en