Response of root respiration and root exudation to alterations in root C supply and demand in wheat |
| |
Authors: | Paul Hill Yakov Kuzyakov David Jones John Farrar |
| |
Institution: | (1) School of Biological Sciences, University of Wales, Bangor, Gwynedd, LL57 2UW, Wales, UK;(2) Department of Agroecosystem Research, University of Bayreuth, 95440 Bayreuth, Germany;(3) School of the Environment and Natural Resources, University of Wales, Bangor, Gwynedd, LL57 2UW, Wales, UK |
| |
Abstract: | Rising atmospheric CO2 concentrations have highlighted the importance of being able to understand and predict C fluxes in plant-soil systems. We
investigated the responses of the two fluxes contributing to below-ground efflux of plant root-dependent CO2, root respiration and rhizomicrobial respiration of root exudates. Wheat (Triticum aestivum L., var. Consort) plants were grown in hydroponics at 20°C, pulse-labelled with 14CO2 and subjected to two regimes of temperature and light (12 h photoperiod or darkness at either 15°C or 25°C), to alter plant
C supply and demand. Root respiration was increased by temperature with a Q
10 of 1.6. Root exudation was, in itself, unaltered by temperature, however, it was reduced when C supply to the roots was reduced
and demand for C for respiration was increased by elevated temperature. The rate of exudation responded much more rapidly
to the restriction of C input than did respiration and was approximately four times more sensitive to the decline in C supply
than respiration. Although temporal responses of exudation and respiration were treatment dependent, at the end of the experimental
period (2 days) the relative proportion of C lost by the two processes was conserved despite differences in the magnitude
of total root C loss. Approximately 77% of total C and 67% of 14C lost from roots was accounted for by root respiration. The ratio of exudate specific activity to CO2 specific activity converged to a common value for all treatments of 2, suggesting that exudates and respired CO2were not composed of C of the same age. The results suggest that the contributions of root and rhizomicrobial respiration
to root-dependent below-ground respiration are conserved and highlight the dangers in estimating short-term respiration and
exudation only from measurements of labelled C. The differences in responses over time and in the age of C lost may ultimately
prove useful in improving estimates of root and rhizomicrobial respiration. |
| |
Keywords: | Respiration Rhizodeposition Root exudation CO2 Temperature Light |
本文献已被 SpringerLink 等数据库收录! |
|