Article

Plant and Soil

, Volume 254, Issue 2, pp 317-327

First online:

Turnover and distribution of root exudates of Zea mays

  • Y. KuzyakovAffiliated withDepartment of Soil Science and Land Evaluation, Institute of Soil Science and Land Evaluation (310), Hohenheim University Email author 
  • , A. RaskatovAffiliated withDepartment of Soil Science and Land Evaluation, Institute of Soil Science and Land Evaluation (310), Hohenheim UniversityDepartment of Ecology, Moscow Agricultural Academy
  • , M. KaupenjohannAffiliated withDepartment of Soil Science, Institute of Ecology

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Abstract

Decomposition and distribution of root exudates of Zea mays L. were studied by means of 14CO2 pulse labeling of shoots on a loamy Haplic Luvisol. Plants were grown in two-compartment pots, where the lower part was separated from the roots by monofilament gauze. Root hairs, but not roots, penetrated through the gauze into the lower part of the soil. The root-free soil in the lower compartment was either sterilized with cycloheximide and streptomycin or remained non-sterile. In order to investigate exudate distribution, 3 days after the 14C labeling, the lower soil part was frozen and sliced into 15, one-mm thick layers using a microtome. Cumulative 14CO2 efflux from the soil during the first 3 days after 14C pulse labeling did not change during plant growth and amounted to about 13–20% of the total recovered 14C (41–55% of the carbon translocated below ground). Nighttime rate of total CO2 efflux was 1.5 times lower than during daytime because of tight coupling of exudation with photosynthesis intensity. The average CO2 efflux from the soil with Zea mays was about 74 μg C g−1 day−1 (22 g C m−2 day−1), although, the contribution of plant roots to the total CO2 efflux from the soil was about 78%, and only 22% was respired from the soil organic matter. Zea mays transferred about 4 g m−2 of carbon under ground during 26 days of growth. Three zones of exudate concentrations were identified from the distribution of the 14C-activity in rhizosphere profiles after two labeling periods: (1) 1–2 (3) mm (maximal concentration of exudates) 2) 3–5 mm (presence of exudates is caused by their diffusion from the zone 1); (3) 6–10 mm (very insignificant amounts of exudates diffused from the previous zones). At the distance further than 10 mm no exudates were found. The calculated coefficient of exudate diffusion in the soil was 1.9 × 10−7 cm2 s−1.

14C pulse labeling exudate diffusion rhizosphere CO2 root exudates soil sterilization Zea mays