Effects of drought and root injury on plant-generated CS2 emissions in soil

Abstract

Conditions under which some plants emit carbon disulfide (CS2) in the soil are unknown. A pot assembly was constructed to measure soil CS 2 emissions by Mimosa pudica under conditions of undisturbed growth, root injury, and drought stress. When M. pudica was grown without disturbance, soil CS 2 emissions were below the limit of detection (~<0.1 ngCS2 mL -I) for the entire 8-wk sampling period. However, when the roots of 6-wk-old M. pudica plants were cut to a depth of 10cm, a maximum of 0.5 and 0.4ngCSzmL -I was emitted within minutes at the 5-and 10-cm depths, respectively. These emissions declined slowly to undetectable levels after 50 min. No detectable CS 2 emissions were observed at the 0-and 15-cm depths. No CS 2 was emitted when 6-wk-old M. pudica plants were subjected to drought stress, however, when the same plants were watered, a maximum of 0.3, 0.4, and 0.5 ng CS 2 mL -1 was emitted within minutes at the 5-, 10-and 15-cm depths, respectively. These emissions were detectable for at least 2hr at the 10-and 15-cm depths. No detectable CS 2 emissions were observed at the 0-cm depth after watering. No detectable CS 2 emissions were observed at any depth under any conditions of undisturbed growth, root injury, or drought stress followed by watering for assemblies containing either no plants or Albizia julibrissin, a plant that is closely related to M. pudica but does not emit CS 2. Mimosa pudica emitted detectable CS 2 under conditions of root injury and rewetting of dry soil but not under conditions of undisturbed growth. Release of such a biocidal sulfide only during conditions of root injury or rewetting of dry soil would be advantageous to M. pudica.

Mechanosensitivity below Ground: Touch-Sensitive Smell-Producing Roots in the Shy Plant Mimosa pudica

“…In the course of these studies and in agreement with previous reports (Hartel and Reeder, 1993;Piluk et al, 1998), we detected a pungent, unpleasant sulfurous odor when 7-d-old gnotobiotically grown plants were dislodged from soil. However, more often than not, it was also observed that, when left undisturbed, neither seedlings germinated in soil nor plants germinated aseptically on agar exhibited an odor detectable to the human subjects performing the experiments.…”

“…S5). This implies that these compounds, when observed previously by GC-MS, were artifacts of the experimental protocol used for their detection (Haines et al, 1989;Farkas et al, 1992;Hartel and Reeder, 1993;Feng and Hartel, 1996;Piluk et al, 1998).…”

“…The identity of the compound represented by m/z 239 is unknown. Despite previous reports that the odor emitted by M. pudica roots is caused by CS 2 (Hartel and Reeder, 1993;Piluk et al, 1998), we never detected CS 2 by DART-HRMS, even though we analyzed more than 100 seedling roots of different ages, under various growth conditions (in soil and on agar), and at different periods in the growing season (spring, summer, fall, and winter). Since CS 2 was detected previously by GC-MS, we conducted GC-MS analyses of SPME fibers exposed to M. pudica root volatiles for 5 min under conditions Figure 3.…”

“…Published studies on the analysis of CS 2 production in Mimosoideae species are similar in that they have all involved (1) detection of CS 2 after root tissue disruption; (2) a significant time delay between tissue disruption and CS 2 analysis; and (3) detection of CS 2 under high GC injector temperature conditions (100°C-250°C; Haines, 1991;Hartel and Reeder, 1993;Feng and Hartel, 1996;Piluk et al, 1998), a factor known to result in rapid and facile degradation of labile organosulfur compounds (Block, 2011). The fact that optimal CS 2 production has been observed only after tissue disruption and a significant delay between tissue rupture and analysis time could mean that the chemistry resulting in the appearance of CS 2 was subsequent to earlier stage reactions that rapidly produced compounds that served as a first line of chemical defense and that were later degraded to CS 2 .…”

“…In previous studies where odor emission from M. pudica roots was reported (Hartel and Haines, 1992;Hartel and Reeder, 1993;Piluk et al, 1998), roots from gnotobiotically grown plants were detached from the aerial parts, washed with water, and subsequently crushed in an air-tight plastic syringe. After a 7-min delay, the headspace of the crushed roots was analyzed by gas chromatography-mass spectrometry (GC-MS).…”