Ecophysiology and Evolution of Resource Use and Low-resource Resistance in Helianthus
Author | : Ashley Marie Rea |
Publisher | : |
Total Pages | : 256 |
Release | : 2018 |
ISBN-10 | : OCLC:1076490355 |
ISBN-13 | : |
Rating | : 4/5 (55 Downloads) |
Book excerpt: A foundational goal of plant ecology is to identify co-varying traits across the climatic and soil environments plants contend with through ecological and evolutionary time. These patterns can be observed in ecological time through trait-trait relationships in favorable and stress environments, and through evolutionary time through trait-trait relationships among species. This dissertation focuses on trait-trait and trait-environment relationships in Helianthus at the ecological and evolutionary scale. Using controlled environmental and ontogenetic conditions, I explored variation in drought resistance and nutrient use efficiency in cultivated H. annuus, and variation in nutrient resorption across wild Helianthus species. In water limitation response studies, I found that resistant genotypes of cultivated H. annuus (as assessed by geometric mean productivity and absolute achene mass of the primary head) exhibit high early stem elongation rate under well-watered conditions. In nutrient limitation response studies, I found that nitrogen and phosphorus acquisition and utilization efficiencies often related differently to performance than predicted by single-nutrient limitation studies. I further find evidence suggesting that root nutrient use efficiency traits are independent are independent from shoot nutrient efficiency traits at lower nutrient levels, and that nitrogen and phosphorus efficiency traits are positively associated. At the evolutionary scale, I examine patterns of nutrient resorption variation across wild Helianthus species in light of the paired influences of constraints and selective pressure on foliar nutrient resorption evolution. Using phylogenetically-informed analyses, I found that nutrient resorption capacity is greater in slower-growing species exhibiting a relatively more resource-conservative leaf functional strategy. Furthermore, native habitat soil fertility does not predict nutrient resorption capacity in this genus. This suggests that nutrient resorption evolution is more closely tied to resource economic strategy than native habitat. In conclusion, this dissertation has expanded knowledge of how individual traits predict yield and productivity across resource supply in the globally important sunflower crop, and elucidated the evolutionary relationship between nutrient resorption, leaf functional traits, and native habitat. These insights may inform studies exploring the genetic or physiological basis of the trait relationships I here describe, which will be important for the development of sunflower as a valuable and sustainable oilseed crop.