Date of Award

Spring 1-1-2018

Document Type

Thesis

Degree Name

Master of Arts (MA)

First Advisor

Barbara Demmig-Adams

Second Advisor

William W. Adams III

Third Advisor

Stacey D. Smith

Abstract

Principal component analysis was used to investigate variation in the anatomical features of the leaf minor veins among several summer annual crops (four symplastic versus four apoplastic phloem loaders) and three ecotypes of Arabidopsis thaliana (winter annual apoplastic loader) grown under multiple environmental conditions. The relationship between photosynthetic capacity and the first two principal components emerging from each analysis was then evaluated to identify the primary minor vein features underpinning photosynthetic capacity. Significant linear relationships between photosynthetic capacity and a principal component loaded by tracheary element cross-sectional areas and volumes per unit leaf area (water flux capacity proxy) was present for all species, emphasizing the importance of water delivery to the leaf in support of photosynthesis regardless of phloem loading mechanism. Significant linear relationships were also found between photosynthetic capacity and principal components loaded by phloem cell numbers and tracheary elements per minor vein as well as the latter two normalized for vein density (proxy for apoplastic phloem loading capacity involving membrane transporters) for all apoplastic loaders (summer annuals and winter annual Arabidopsis thaliana). Lastly, a significant linear relationship between photosynthetic capacity and a principal component loaded by phloem cell cross-sectional areas and volumes per unit leaf area (proxy for symplastic loading capacity involving cytosolic enzymes for companion cells) was revealed for summer annual symplastic loaders as well as for A. thaliana (in the case of sieve elements, a proxy for sugar export capacity from the leaves).

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Plant Biology Commons

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