Degree
Doctor of Philosophy (PhD)
Department
School of Plant, Environmental, and Soil Sciences
Document Type
Dissertation
Abstract
In sweetpotato, successful storage root (SR) initiation requires the establishment of sink strength in competent ARs capable of attracting and utilizing photoassimilates. Sucrose synthase (SuSy), a key enzyme involved in sucrose cleavage and carbon partitioning, is recognized as a marker of sink strength in competent ARs; however, the signals regulating its induction during SR initiation remain unclear. This work tested the hypothesis that declining phosphorus (P) and nitrogen (N) availability enhance sink strength in competent ARs through increased SuSy activity and investigated root system architecture (RSA) traits associated with adaptation to episodic drought. Greenhouse experiments evaluated SuSy responses to P and N availability, cultivar-specific nutrient responsiveness, and RSA and SR development under simulated episodic drought. Results revealed that adventitious root proximal tissue (APT), the tissue-specific associated with anomalous cambium formation, exhibited the strongest SuSy induction during SR initiation among the tissues examined. Declining P and N availability increased SuSy activity at 10 and 15d, whereas complete nutrient deprivation failed to sustain elevated responses, demonstrating a threshold-dependent relationship between nutrient availability and sink establishment. Cultivars differed in SuSy responsiveness to declining N and P, with ‘Beauregard’, ‘Bayou Belle’, and ‘Orleans’ exhibiting stronger induction than ‘Evangeline’ and ‘Okinawa. Under episodic drought, the breeding line LA11-88 maintained greater root growth following episodic drought and more stable SR development, indicating greater RSA plasticity and recovery capacity. Taken together, the results provide a physiological framework for understanding nutrient-mediated sink establishment and identify nutrient responsiveness and RSA plasticity as potential targets for cultivar selection and breeding to improve SR formation, yield stability, and adaptation to variable growing environments.
Date
10-6-2026
Recommended Citation
Barbosa, Marissa B., "From Signals to Sinks: Integrating Nutrient Signaling and Root Architectural Traits to Enhance Sink Strength and Drought Adaptation in Sweetpotato" (2026). LSU Doctoral Dissertations. 7210.
https://repository.lsu.edu/gradschool_dissertations/7210
Committee Chair
LaBonte, Don
LSU Acknowledgement
1
LSU Accessibility Acknowledgment
1