Sudden cold temperature delays plant carbon transport and shifts allocation from growth to respiratory demand

[摘要] Since substrates for respiration are supplied mainly by recentphoto-assimilates, there is a strong but time-lagged link between short-termabove- and belowground carbon (C) cycling. However, regulation of thiscoupling by environmental variables is poorly understood. Whereas recentstudies focussed on the effect of drought and shading on the link betweenabove- and belowground short-term C cycling, the effect of temperatureremains unclear.

We used a ¹³CO₂ pulse-chase labelling experiment to investigate theeffect of a sudden temperature change from 25to 10 °C onthe short-term coupling between assimilatory C uptake and respiratory loss.The study was done in the laboratory using two-month-old perennial rye-grassplants (Lolium perenne L.). After label application, the δ¹³C signal of respired shoot and root samples was analysed at regulartime intervals using laser spectroscopy. In addition, δ¹³C wasanalysed in bulk root and shoot samples.

Cold temperature (10 °C) reduced the short-term coupling betweenshoot and roots by delaying belowground transfer of recent assimilates andits subsequent respiratory use, as indicated by the δ¹³C signal ofroot respiration (δ¹³C_RR). That is, the time lag fromthe actual shoot labelling to the first appearance of the label in¹³C_RR was about 1.5 times longer under cold temperature.Moreover, analysis of bulk shoot and root material revealed that plants atcold temperature invest relatively more carbon into respiration compared togrowth or storage. While the whole plant C turnover increased under coldtemperature, the turnover time of the labile C pool decreased, probablybecause less ¹³C is used for growth and/or storage. That is, (almost)all recent C remained in the labile pool serving respiration under theseconditions. Overall, our results highlight the importance of temperature as adriver of C transport and relative C allocation within the plant–soil system.

[学科分类] 地球化学与岩石