Carbon efflux rates of fine roots of three tree species decline shortly after excision

• Published in: Environmental and experimental botany 1997-12, Vol.38 (3), p.243-249
• Main Authors: Rakonczay, Zoltán, Seiler, John R., Kelting, Daniel L.
• Format: Article
• Language: English
• Subjects: Acer rubrum; Agronomy. Soil science and plant productions; Biological and medical sciences; Economic plant physiology; Fundamental and applied biological sciences. Psychology; Metabolism; Net assimilation, photosynthesis, carbon metabolism. Photorespiration, respiration, fermentation (anoxia, hypoxia); Nutrition. Photosynthesis. Respiration. Metabolism; Photosynthesis, respiration. Anabolism, catabolism; Pinus strobus; Plant physiology and development; Quercus rubra; Root respiration; Time response
• ISSN: 0098-8472; 1873-7307
• DOI: 10.1016/S0098-8472(97)00014-2

Fine roots (diameter ≦2 mm) of Acer rubrum, Quercus rubra and Pinus strobus were used to determine whether respiration rates (measured as CO 2 efflux rates) remain sufficiently stable for the 1 min to 10 h interval after excision to allow reliable measurements to be taken. Roots of five individuals of each species were excavated from the upper 10 cm of the soil. From each tree, two samples of roots (dry weights between 0.21 and 1.18 g) were excised and immediately subjected to one of two treatments. The attached soil was removed mechanically with (wet treatment) or without (dry treatment) the further removal of soil by submersion in and rinsing with water. Within 1 min of excision, roots were placed in a gas exchange system and their respiration was measured. The measurements were repeated 5, 15, 30 min and 1, 2 ( Acer and Pinus), 3 ( Quercus), 6 and 10 h after excision. For all species, carbon efflux rates showed a marked decline over time, dropping significantly ( p ≤ 0.05) over 5 min for Acer and Pinus and over 15 min for Quercus (by 37, 52 and 33%, respectively). The initial rates (12.9, 9.2 and 8.7 nmol CO 2 g −1 s −1 at 25 °C for Acer, Quercus and Pinus, respectively) declined to a minimum (4.2, 2.9 and 4.4 nmol CO 2 g −1 s −1) in 30 ( Pinus) or 60 ( Acer and Quercus) min then levelled off ( Acer and Quercus) or started to increase ( Pinus). Possible mechanisms causing the decline are discussed.