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Leaf respiration

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Protocols
This section is intended for protocols relating to:
- oxygen electrodes,
- IRGAs
- leaf/root material
- temperature response of respiration

Summary

Characterising leaf dark respiration (Rleaf) in a fashion that enables comparison among species and especially among sites and times of year is challenging, given the sensitivity and acclimation of Rleaf to temperature. However Rleaf under typical field conditions is valuable because it is both a measure of basal metabolism and a rough correlate of average realised night-time respiratory C flux. Rleaf scales with other metabolic, structural, chemical and longevity aspects of the leaf economic spectrum and, along with those other variables, enables scaling to canopy processes of whole ecosystems.

Contributing author

This article is modified from Perez-Harguindeguy et al (2013). The "New handbook for standardised measurement of plant functional traits worldwide" is a product of and is hosted by Nucleo Diversus (with additional Spanish translation). For more on this trait and on its context as part of the entire trait handbook visit its primary site Nucleo DiverSus at http://www.nucleodiversus.org/?lang=en

Procedure

What, when and how to measure?

Sample young to medium-aged fully expanded leaves (see SLA) to ensure negligible respiration associated with biosynthesis (‘growth respiration’). Do not make measurements during or soon after atypical conditions (such as e.g. heat or cold stress, water stress), unless that is the focus of the research. Sample foliage from parts of the canopy sunlit during daytime, unless one is specifically focussed on the shaded understorey taxa. If possible, measure intact leaves at night. In any case, leaves must have been in the dark for ~30 min to minimise variation resulting from very recently fixed photosynthate or transient light-induced respiratory CO2 losses.

Any reliable leaf gas-exchange system that can control leaf temperature can be used. If possible, it is best to measure intact foliage. Detached leaves should be kept moist, cool (to minimise C and water loss), and in the dark until measurement. If possible, tests of intact v. detached foliage should be made for a subsample, to ensure that similar rates are observed. See Light saturated photosynthetic rate for any subsequent leaf handling.

Leaf dark respiration(Rleaf) can be measured while measuring photosynthetic rate (see Light saturated photosynthetic rate), merely by turning off, or shielding, the chamber completely from incident light. However, flux rates for Rleaf are roughly an order of magnitude lower than those for Amax and, therefore, the signal to noise ratio of the typical portable photosynthesis system may be suboptimal for taxa with lower flux rates. One can reduce flow rates and/or increase the amount of foliage into the chamber, to alleviate this problem; however, this is not always sufficient to obtain reliable measurements. In such cases, using specialised chambers (which may hold more foliage) and/or choosing a standardised temperature that is at the high rather than low end of the candidate range (next paragraph) can help ameliorate this problem by increasing the flux rate.

For comparative Rleaf measurements, one typically chooses a standardised temperature appropriate for the site conditions (e.g. 25°C in the tropics, 20°C in the temperate zone, 10°C or 15°C in cold boreal or summer tundra conditions). However, because cross-study comparisons are often made of taxa grown in and/or measured under different temperatures, instantaneous temperature response functions can help in calibrating respiration across temperature regimes. Where possible, measure (subsets of) leaves at appropriate contrasting measurement temperatures, with 10°C intervals, or ideally at least four different temperatures over a 15–35°C range.

Literature references

References on theory,significance and large datasets

Atkin OK, Bruhn D, Hurry VM, Tjoelker MG (2005) The hot and the cold: unravelling the variable response of plant respiration to temperature. Functional Plant Biology 32, 87–105. doi:10.1071/FP03176
 
Reich PB, Tjoelker MG, Walters MB, Vanderklein DW, Bushena C (1998) Close association of RGR, leaf and root morphology, seed mass and shade tolerance in seedlings of nine boreal tree species grown in high and low
light. Functional Ecology 12, 327–338. doi:10.1046/j.1365-2435.1998.00208.x
 
Reich PB, Tjoelker MG, Pregitzer KS, Wright IJ, Oleksyn J, Machado JL (2008) Scaling of respiration to nitrogen in leaves, stems and roots of higher land plants. Ecology Letters 11, 793–801. doi:10.1111/j.1461-0248.2008.01185.x
 
Rodriguez-Calcerrada J, Atkin OK, Robson TM, Zaragoza-Castells J, Gil L, Aranda I (2010) Thermal acclimation of leaf dark respiration of beech seedlings experiencingsummerdrought in highandlowlight environments. Tree Physiology 30, 214–224. doi:10.1093/treephys/tpp104
 
Tjoelker MG, Oleksyn J, Reich PB (2001) Modelling respiration of vegetation: evidence for a general temperature-dependent Q10. Global Change Biology 7, 223–230. doi:10.1046/j.1365-2486.2001.00397.x
 
Wright IJ, Reich PB, Westoby M, Ackerly DD, Baruch Z, Bongers F, Cavender-Bares J, Chapin T, Cornelissen JHC, Diemer M, Flexas J, Garnier E, Groom PK, Gulias J, Hikosaka K, Lamont BB, Lee T, Lee W, Lusk C, Midgley JJ, NavasML, Niinemets U, Oleksyn J, Osada N, Poorter H, Poot P, Prior L, Pyankov VI, Roumet C, Thomas SC, Tjoelker MG, Veneklaas EJ, Villar R (2004) The worldwide leaf economics spectrum. Nature 428, 821–827. doi:10.1038/nature02403

 


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