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Summary High concentrations of dissolved inorganic carbon in stems of herbaceous and woody C3plants exit leaves in the dark. In the light, C3species use a small portion of xylem‐transported CO2for leaf photosynthesis. However, it is not known if xylem‐transported CO2will exit leaves in the dark or be used for photosynthesis in the light in Kranz‐type C4plants.Cut leaves ofAmaranthus hypochondriacuswere placed in one of three solutions of [NaH13CO3] dissolved in KCl water to measure the efflux of xylem‐transported CO2exiting the leaf in the dark or rates of assimilation of xylem‐transported CO2* in the light, in real‐time, using a tunable diode laser absorption spectroscope.In the dark, the efflux of xylem‐transported CO2increased with increasing rates of transpiration and [13CO2*]; however, rates of13CeffluxinA. hypochondriacuswere lower compared to C3species. In the light,A. hypochondriacusfixed nearly 75% of the xylem‐transported CO2supplied to the leaf.Kranz anatomy and biochemistry likely influence the efflux of xylem‐transported CO2out of cut leaves ofA. hypochondriacusin the dark, as well as the use of xylem‐transported CO2* for photosynthesis in the light. Thus increasing the carbon use efficiency of Kranz‐type C4species over C3species.
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How megadrought causes extensive mortality in a deep‐rooted shrub species normally resistant to drought‐induced dieback: The role of a biotic mortality agent
Abstract Southern California experienced unprecedented megadrought between 2012 and 2018. During this time,Malosma laurina, a chaparral species normally resilient to single‐year intense drought, developed extensive mortality exceeding 60% throughout low‐elevation coastal populations of the Santa Monica Mountains. We assessed the physiological mechanisms by which the advent of megadrought predisposedM. laurinato extensive shoot dieback and whole‐plant death. We found that hydraulic conductance of stem xylem (Ks, native) was reduced seven to 11‐fold in dieback adult and resprout branches, respectively. Staining of stem xylem vessels revealed that dieback plants experienced 68% solid‐blockage, explaining the reduction in water transport. Following Koch's postulates, persistent isolation of a microorganism in stem xylem of dieback plants but not healthy controls indicated that the causative agent of xylem blockage was an opportunistic endophytic fungus,Botryosphaeria dothidea. We inoculated healthyM. laurinasaplings with fungal isolates and compared hyphal elongation rates under well‐watered, water‐deficit, and carbon‐deficit treatments. Relative to controls, we found that both water deficit and carbon‐deficit increased hyphal extension rates and the incidence of shoot dieback.
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- Award ID(s):
- 1950350
- PAR ID:
- 10477801
- Publisher / Repository:
- Wiley-Blackwell
- Date Published:
- Journal Name:
- Plant, Cell & Environment
- ISSN:
- 0140-7791
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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