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Impact of light quality on leaf and shoot hydraulic properties: a case study in silver birch (Betula pendula)
- SELLIN, ARNE, SACK, LAWREN, ÕUNAPUU, EELE, KARUSION, ANNIKA
- Plant, cell and environment 2011 v.34 no.7 pp. 1079-1087
- Betula pendula, blue light, branches, canopy, case studies, energy, exposure duration, forest stands, gas exchange, leaf blade, leaf conductance, light intensity, light quality, petioles, receptors, red light, shade, shoots, steady flow, temperate forests, trees, white light
- Responses of leaf and shoot hydraulic conductance to light quality were examined on shoots of silver birch (Betula pendula), cut from lower (‘shade position') and upper thirds of the crowns (‘sun position') of trees growing in a natural temperate forest stand. Hydraulic conductances of leaf blades (Klb), petioles (KP) and branches (i.e. leafless stem; KB) were determined using a high pressure flow meter in steady state mode. The shoots were exposed to photosynthetic photon flux density of 200-250 µmol m⁻² s⁻¹ using white, blue or red light. Klb depended significantly on both light quality and canopy position (P < 0.001), KB on canopy position (P < 0.001) and exposure time (P = 0.014), and none of the three factors had effect on KP. The highest values of Klb were recorded under the blue light (3.63 and 3.13 × 10⁻⁴ kg m⁻² MPa⁻¹ s⁻¹ for the sun and shade leaves, respectively), intermediate values under white light (3.37 and 2.46 × 10⁻⁴ kg m⁻² MPa⁻¹ s⁻¹, respectively) and lowest values under red light (2.83 and 2.02 × 10⁻⁴ kg m⁻² MPa⁻¹ s⁻¹, respectively). Light quality has an important impact on leaf hydraulic properties, independently of light intensity or of total light energy, and the specific light receptors involved in this response require identification. Given that natural canopy shade depletes blue and red light, Klb may be decreased both by reduced fluence and shifts in light spectra, indicating the need for studies of the natural heterogeneity of Klb within and under canopies, and its impacts on gas exchange.