Is leaf pubescence of Cape Proteaceae a xeromorphic or radiation-protective trait?

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doi:10.1071/BT11231

Southern Hemisphere Botanical Ecosystems

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Protocols in ecological and environmental plant physiology

Is leaf pubescence of Cape Proteaceae a xeromorphic or radiation-protective trait?

R. P. Skelton ^A ^D, J. J. Midgley ^A, J. M. Nyaga ^A, S. D. Johnson ^B and M. D. Cramer ^A ^C

^A Department of Botany, University of Cape Town, Private Bag XI, Rondebosch 7701, South Africa.
^B School of Biological and Conservation Sciences, University of KwaZulu-Natal, Private Bag X01, Scottsville, Pietermaritzburg 3209, South Africa.
^C School of Plant Biology, Faculty of Natural and Agricultural Sciences, The University of Western Australia, 35 Stirling Highway, WA 6009, Australia.
^D Corresponding author. Email: skelrob@gmail.com

Australian Journal of Botany 60(2) 104-113 http://dx.doi.org/10.1071/BT11231
Submitted: 8 September 2011 Accepted: 13 January 2012 Published: 6 March 2012





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Abstract

Although pubescence has traditionally been considered to be related to the water economy of plants, the results are ambivalent and vary between different species. We tested two contrasting hypotheses for the functional significance of leaf pubescence of Proteaceae species from the Cape Floristic Region. First, we hypothesised that pubescence is a xeromorphic trait that conserves water by increasing the boundary layer resistance to diffusion. Water loss was measured in two morphotypes of Leucospermum conocarpodendron (L.) Buek that differ in the degree of leaf pubescence, using both gas exchange and gravimetric techniques. Pubescence contributed less than 5% of total leaf resistance and pubescent leaves transpired at least as rapidly as glabrous leaves due to having larger numbers of small stomata per leaf area. Although pubescence was not associated with drier sites in L. conocarpodendron, there was a weak negative correlation between rainfall and pubescence across 18 other Proteaceae species. We also hypothesised that pubescence is a radiation-protective trait. We assessed the effect of pubescence on light reflectance, leaf temperature, fluorescence and gas exchange characteristics in situ. Pubescent leaves of L. conocarpodendron were 19.2 ± 0.08% more reflective than glabrous leaves and had significantly greater pre-dawn photochemical efficiency. There was a positive association between leaf pubescence and habitat temperature in Proteaceae. We conclude that although pubescence is unlikely to be a xeric adaptation, it could serve a role in reducing photoinhibition and heat loading in Proteaceae species.

References

Allsopp N, Stock WD (1994) VA mycorrhizal infection in relation to edaphic characteristics and disturbance regime in three lowland plant communities in the south-western Cape, South Africa. Journal of Ecology 82, 271–279.
| CrossRef |

Benz BW, Martin CE (2006) Foliar trichomes, boundary layers, and gas exchange in 12 species of epiphytic Tillandsia (Bromeliaceae). Journal of Plant Physiology 163, 648–656.
| CrossRef | CAS |

Benzing DH, Henderson K, Kessel B, Sulak J (1976) The absorptive capacities of Bromeliad trichomes. American Journal of Botany 63, 1009–1014.
| CrossRef |

Brodribb TJ, McAdam SAM, Jordan GJ, Feild TS (2009) Evolution of stomatal responsiveness to CO₂ and optimisation of water-use efficiency among land plants. New Phytologist 183, 839–847.
| CrossRef |

Close DC, McArthur C (2002) Rethinking the role of many plant phenolics – protection from photodamage not herbivores? Oikos 99, 166–172.
| CrossRef | CAS |

Close DC, Davidson NJ, Shields CB, Wiltshire R (2007) Reflectance and phenolics of green and glaucous leaves of Eucalyptus urnigera. Australian Journal of Botany 55, 561–567.
| CrossRef |

Ehleringer J (1984) Ecology and ecophysiology of leaf pubescence in North American desert plants. In ‘Biology and chemistry of plant trichomes’. (Eds E Rodriguez, PL Healey, I Mehta) pp. 113–132. (Plenum Press: New York)

Ehleringer J, Mooney HA (1978) Leaf hairs: effects on physiological activity and adaptive value to a desert shrub. Oecologia 37, 183–200.
| CrossRef |

Ehleringer J, Björkman O, Mooney HA (1976) Leaf pubescence: effects on absorptance and photosynthesis in a desert shrub. Science 192, 376–377.
| CrossRef | CAS |

Farquhar GD, Ehleringer JR, Hubick KT (1989) Carbon isotope discrimination and photosynthesis. Annual Review of Plant Physiology and Plant Molecular Biology 40, 503–537.
| CrossRef | CAS |

Franks PJ, Beerling DJ (2009) Maximum leaf conductance driven by CO₂ effects on stomatal size and density over geologic time. Proceedings of the National Academy of Sciences of the United States of America 106, 10343–10347.
| CrossRef | CAS |

Galley C, Linder HP, Zimmermann NE (2009) Pentaschistis (Poaceae) diversity in the Cape Mediterranean region: habitat heterogeneity and climate stability. Global Ecology and Biogeography 18, 586–595.
| CrossRef |

Galmés J, Medrano H, Flexas J (2007) Photosynthesis and photoinhibition in response to drought in a pubescent (var. minor) and a glabrous (var. palaui) variety of Digitalis minor. Environmental and Experimental Botany 60, 105–111.
| CrossRef |

Hassiotou F, Evans JR, Ludwig M, Veneklaas EJ (2009) Stomatal crypts may facilitate diffusion of CO₂ to adaxial mesophyll cells in thick sclerophylls. Plant, Cell & Environment 32, 1596–1611.
| CrossRef | CAS |

Johnson HB (1975) Plant pubescence: an ecological perspective. Botanical Review 41, 233–258.
| CrossRef |

Jordan GJ, Dillon RA, Weston PH (2005) Solar radiation as a factor in the evolution of scleromorphic leaf anatomy in Proteaceae. American Journal of Botany 92, 789–796.
| CrossRef |

Jordan GJ, Weston PH, Carpenter RJ, Dillon RA, Brodribb TJ (2008) The evolutionary relations of sunken, covered, and encrypted stomata to dry habitats in Proteaceae. American Journal of Botany 95, 521–530.
| CrossRef |

Kramer PJ, Boyer JS (1995) ‘Water relations of plants and soils.’ (Academic Press: San Diego)

Lamont BB, Groom PK, Cowling RM (2002) High leaf mass per area of related species assemblages may reflect low rainfall and carbon isotope discrimination rather than low phosphorous and nitrogen concentrations. Functional Ecology 16, 403–412.
| CrossRef |

Linder HP (2003) The radiation of the Cape flora, southern Africa. Biological Reviews of the Cambridge Philosophical Society 78, 597–638.
| CrossRef | CAS |

Martin TA, Hinckley TM, Meinzer FC, Sprugel DG (1999) Boundary layer conductance, leaf temperature and transpiration of Abies amabilis branches. Tree Physiology 19, 435–443.

Maxwell K, Johnson GN (2000) Chlorophyll fluorescence – a practical guide. Journal of Experimental Botany 51, 659–668.
| CrossRef | CAS |

Meinzer F, Goldstein G (1985) Some consequences of leaf pubescence in the Andean giant rosette plant Espeletia timotensis. Ecology 66, 512–520.
| CrossRef |

Mozafar A, Goodin JR (1970) Vesiculated hairs: a mechanism for salt tolerance in Atriplex halimus L. Plant Physiology 45, 62–65.
| CrossRef | CAS |

Nishiyama Y, Allakhverdiev SI, Murata N (2006) A new paradigm for the action of reactive oxygen species in the photoinhibition of photosystem II. Biochimica et Biophysica Acta - Bioenergetics 1757, 742–749.
| CrossRef | CAS |

Nobel PS (2005) ‘Physicochemical and environmental plant physiology.’ (Elsevier Academic Press: Amsterdam)

Procheş Ş, Cowling RM, du Preez DM (2005) Patterns of geophyte diversity and storage organ size in the winter-rainfall region of southern Africa. Diversity & Distributions 11, 101–109.
| CrossRef |

Rebelo T (2001) ‘Proteas: a field guide to the proteas of southern Africa.’ (Fernwood Press: Cape Town)

Richardson DM, Cowling RM, Bond WJ, Stock WD, Davis GW (1995) Links between biodiversity and ecosystem function in the Cape Floristic Region. In Mediterranean-type ecosystems: the function of biodiversity (Eds GW Davis, DM Richardson). pp. 285–333. (Springer-Verlag: Berlin)

Ripley BS, Pammenter NW, Smith VR (1999) Function of leaf hairs revisited: the hair layer on leaves of Arctotheca populifolia reduces photoinhibition, but leads to higher leaf temperatures caused by lower transpiration rates. Journal of Plant Physiology 155, 78–85.
| CrossRef | CAS |

Rotondi A, Rossi F, Asunis C, Cesaraccio C (2003) Leaf xeromorphic adaptations of some plants of a coastal Mediterranean macchia ecosystem. Journal of Mediterranean Ecology 4, 25–35.

Rourke JP (1972) Taxonomic studies on Leucospermum R.Br. Journal of South African Botany 8, 1–194.

Schuepp PH (1993) Tansley Review no. 59. Leaf boundary layers. New Phytologist 125, 477–507.
| CrossRef |

Schulze RE (1997) ‘South African atlas of agrohydrology and climatology.’ (Water Research Commission: Pretoria)

Skaltsa H, Verykokidou E, Harvala C, Karabourniotis G, Manetas Y (1994) UV-B protective potential and flavonoid content of leaf hairs of Quercus ilex. Phytochemistry 37, 987–990.
| CrossRef | CAS |

Smith M (1986) Camp’s Bay reservoir revegetation. Honours Thesis, University of Cape Town.

Thimijan RW, Heins RD (1983) Photometric, radiometric, and quantum light units of measure: a review of procedures for interconversion. HortScience 18, 818–822.

Turner IM (1994) Sclerophylly: primarily protective? Functional Ecology 8, 669–675.
| CrossRef |

Verboom GA, Linder HP, Stock WD (2004) Testing the adaptive nature of radiation: growth form and life history divergence in the African grass genus Ehrharta (Poaceae: Ehrhartoideae). American Journal of Botany 91, 1364–1370.
| CrossRef |

Witkowski ETF, Mitchell DT (1987) Variations in soil phosphorous in the Fynbos biome, South Africa. Journal of Ecology 75, 1159–1171.
| CrossRef |

Wuenscher JE (1970) The effect of leaf hairs of Verbascum thapsus on leaf energy exchange. New Phytologist 69, 65–73.
| CrossRef |

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