plant surface microbiology.pdf

3 Methaogenic Microbial Communities Asociated with Aquatic Plants 39
Fig. 2. Transfer of carbon via rice
plants to the soil and into CH 4 .
Above After pulse labeling of the
rice plants with 14 CO 2 , radioactivity
transiently accumulates in soil
organic compounds and is ultimately
converted to 14 CH 4 ; below
specific radioactivities indicate
that radioactive compounds are
converted in the sequence lactate>propionate>acetate>CH
4
(taken from Dannenberg and Conrad
1999)
Radioactivity [Bq ml -1 ]
Specific radioactivity [Bq nmol -1 ]
500
400
300
200
100
Experiment #1
lactate
propionate
acetate
CH 4
0
0 2 4 6 8 10 12 14 16
Time [d]
0
0 2 4 6
Besides the more direct effect of photosynthesis through root exudation,
CH 4 production in wetlands is furthermore stimulated by plant debris. This
may be decaying roots or dead aboveground plant material. In rice fields, for
example, rice straw from the previous season is often plowed under to
improve soil quality. Also, composted plant material is used as soil fertilizer.
There are numerous studies which show that addition of such organic matter
dramatically increases CH 4 emission rates (Denier van der Gon 1999).
Decomposition of isotopically labeled rice straw contributes significantly to
production and emission of CH 4 during the early season (Chidthaisong and
Watanabe 1997; Watanabe et al. 1998, 1999)
8
7
6
5
4
3
2
1
Time [d]
A
lactate
propionate
acetate
CO 2
CH 4
B