Journal
PHYSIOLOGIA PLANTARUM
Volume 175, Issue 5, Pages -Publisher
WILEY
DOI: 10.1111/ppl.14035
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This study investigated the physiological responses of a resurrection plant during the dehydration and rehydration process. The results showed that the plant adjusted its photosynthesis and stomatal conductance to delay dehydration and prepare for desiccation. Complete rehydration occurred rapidly in the mesophyll, while the refilling of xylem and subsequent recovery of photosynthesis occurred at later stages. These findings highlight the importance of stomata in protecting the vascular system from embolism even in desiccation-tolerant plants.
The main parameters determining photosynthesis are stomatal and mesophyll conductance and electron transport rate, and for hydraulic dynamics they are leaf hydraulic conductance and the spread of embolism. These parameters have scarcely been studied in desiccation-tolerant (resurrection) plants exposed to drought. Here, we characterized photosynthesis and hydraulics during desiccation and rehydration in a poikilochlorophyllous resurrection plant, Barbacenia purpurea (Velloziaceae). Gas exchange, chlorophyll fluorescence, and leaf water status were monitored along the whole dehydration-rehydration cycle. Simultaneously, embolism formation and hydraulic functioning recovery were measured at leaf level using micro-computed tomography imaging. Photosynthesis and leaf hydraulic conductance ceased at relatively high water potential (-1.28 and -1.54 MPa, respectively), whereas the onset of leaf embolism occurred after stomatal closure and photosynthesis cessation (<-1.61 MPa). This sequence of physiological processes during water stress may be associated with the need to delay dehydration, to prepare the molecular changes required in the desiccated state. Complete rehydration occurred rapidly in the mesophyll, whereas partial xylem refilling, and subsequent recovery of photosynthesis, occurred at later stages after rewatering. These results highlight the importance of stomata as safety valves to protect the vascular system from embolism, even in a plant able to fully recover after complete embolism.
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