Variations in dark respiration and mitochondrial numbers within needles of Pinus radiata grown in ambient or elevated CO2 partial pressure

Home

Editors

Contents

Contact

Tree Physiology, 24:347–353

[ Free PDF ] [ Return to Contents ] [ Export citation ]

Variations in dark respiration and mitochondrial numbers within needles of Pinus radiata grown in ambient or elevated CO₂ partial pressure

Kevin L. Griffin (1, 2), O. Roger Anderson (1), David T. Tissue (3), Matthew H. Turnbull (4) and David Whitehead (5)

1. Lamont-Doherty Earth Observatory of Columbia University, Palisades, NY 10964, USA / 2. Corresponding author (griff@LDEO.columbia.edu) / 3. Department of Biology, Texas Tech University, Lubbock, TX 79409, USA / 4. Department of Plant and Microbial Sciences, University of Canterbury, Christchurch, New Zealand / 5. Landcare Research, P.O. Box 69, Lincoln 8152, New Zealand / Received April 3, 2003; accepted September 5, 2003; published online January 2, 2004

Summary

Within-leaf variations in cell size, mitochondrial numbers and dark respiration rates were compared in the most recently expanded tip, the mid-section and base of needles of Pinus radiata D. Don trees grown for 4 years in open-top chambers at ambient (36 Pa) or elevated (65 Pa) carbon dioxide partial pressure (p(CO₂)_a). Mitochondrial numbers and respiratory activity varied along the length of the needle, with the highest number of mitochondria per unit cytoplasm and the highest rate of respiration per unit leaf area at the base of the needle. Regardless of the location of the cells (tip, middle or basal sections), needles collected from trees grown in elevated p(CO₂)_a had nearly twice the number of mitochondria per unit cytoplasm as those grown in ambient p(CO₂)_a. This stimulation of mitochondrial density by growth at elevated p(CO₂)_a was greater at the tip of the needle (2.7 times more mitochondria than in needles grown in ambient CO₂) than at the base of the needle (1.7 times). The mean size of individual mitochondria was unaffected either by growth at elevated p(CO₂)_a or by position along the needle. Tree growth at elevated p(CO₂)_a had a variable effect on respiration per unit leaf area, significantly increasing respiration in the tip of the needles (+25%) and decreasing respiration at the mid-section and base of the needles (–14% and –25%, respectively). Although a simple relationship between respiration per unit leaf area and mitochondrial number per unit cytoplasm was found within each CO₂ treatment, the variable effect of growth at elevated p(CO₂)_a on respiration along the length of the needles indicates that a more complex relationship must determine the association between structure and function in these needles.

Keywords: peroxisomes, transfusion tissue, ultrastructure.