Plant water transport and photosynthesis in water-limited environments
| dc.contributor.advisor | Katul, Gabriel G | |
| dc.contributor.author | Mrad, Assaad | |
| dc.date.accessioned | 2021-01-12T22:27:20Z | |
| dc.date.available | 2021-01-12T22:27:20Z | |
| dc.date.issued | 2020 | |
| dc.department | Environment | |
| dc.description.abstract | Terrestrial ecosystems depend on vegetation for many indispensable services including carbon fixation from the atmosphere, food production, and the maintenance of the global water and carbon cycles. As the climate changes, temperature and precipitation patterns shift and extreme climatic events become more frequent. In many areas, droughts are increasing in intensity and frequency, posing a challenge to ecosystem health and food security. Plants depend on water for physiological functioning including photosynthesis. The ability of plants to continue supplying water to the leaves from the soil during droughts depends on the anatomy and structure of its vascular network, the xylem. Droughts cause gas bubbles, or embolisms, to spread within the xylem, blocking water movement. A combination of modeling water flow in xylem of flowering plants and theoretical considerations derived from graph theory is used to explain the response of different xylem functional types to droughts. An open-source model of plant xylem hydraulics was developed with which it was shown how 'network' effects, such as the spatial distribution of anatomy throughout growth rings, alter the response of Maples to drought. The xylem of similar flowering plants was further investigated through the model in addition to the the physics of percolation. This was the first instance percolation theory has ever been applied to embolism spread inside xylem. It was shown how embolism spread inside the xylem can be represented by an edge percolation process. The results indicate that an increased connectivity among the conduits in the xylem is a necessary feature in plant organs that are resistant to droughts. The detrimental effects of droughts on plant water translocation cascade to inhibit photosynthesis. Soil-to-leaf resistance to drought is represented by a vulnerability to embolism curve (VC) that plots the percent loss in plant hydraulic conductivity as water potential declines. The whole-plant VC affects plant CO2 fixation under drought. The results show how different VC shapes give rise to typical isohydric and anisohydric plant responses to drought. To arrive at this conclusion, the calculus of variations is used to integrate plant hydraulics into the trade-off between CO2 fixation and transpiration during a drought. | |
| dc.identifier.uri | ||
| dc.subject | Environmental science | |
| dc.subject | Drought | |
| dc.subject | Embolism | |
| dc.subject | Percolation | |
| dc.subject | Photosynthesis | |
| dc.subject | Xylem | |
| dc.title | Plant water transport and photosynthesis in water-limited environments | |
| dc.type | Dissertation |