Radiocarbon Suggests the Hemiparasitic Annual Melampyrum Lineare Desr. May Acquire Carbon from Stressed Hosts
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Hemiparasitic plants obtain water and solutes from their hosts, but much remains to be learned about these transfers. We used a forest girdling experiment to investigate how leaf gas exchange, carbon and nitrogen cycling in the root hemiparasite Melampyrum lineare Desr. responded to disturbance and changes in physiology of potential host trees. By preventing belowground C allocation by 35% of the canopy, girdling decreased the starch and soluble sugar contents of bulk forest floor fine roots. Photosynthetic rates of M. lineare were statistically significantly lower in the girdled plot, but their hypothesized drivers (foliar N, stomatal conductance and transpiration) had no statistically significant differences between girdled and non-girdled plots. However, M. lineare in the girdled plot had higher foliar C concentrations and Δ14C than in the control plot, suggesting possible photosynthetic down-regulation in the girdled plot due to influx of older (e.g., host-derived) C into the leaves of M. lineare. Within the girdled plot (but not the control plot), M. lineare foliar C concentrations were positively correlated with foliar Δ14C and δ15N, suggesting that M. lineare may respond to changes in both C and N biogeochemistry during the decline of dominant canopy species.
Keywordsnonstructural carbohydrates; physiological stress; photosynthesis; plant mixotrophy; transpiration
Nave, Lucas E; Heckman, Katherine A; Muñoz, Alexandra B; Swanston, Christopher W. 2018. Radiocarbon Suggests the Hemiparasitic Annual Melampyrum Lineare Desr. May Acquire Carbon from Stressed Hosts. Radiocarbon. 60(01): 269-281. https://doi.org/10.1017/RDC.2017.97.