Master's Theses

Document Type

Thesis

Date of Award

Spring 2019

Degree Name

Master of Science (MS)

Department

Biology

Advisor

Dr. Brian Maricle

Abstract

to the heterogeneity of habitats, all plants are exposed to at least some degree of shade during their lifetime. Reduced light intensity, drops in R:FR ratio, and limited blue light are cues for plants to perceive competition; the shade avoidance syndrome (SAS) is common for grassland species while shade tolerance (ST) is common for forest species when competition is perceived. SAS is characterized by elongation of stems and petioles, reduced branches, decreased leaf area, decreased shoot biomass, and increased number of ramets. ST is characterized by little elongation of stems and petioles, high chlorophyll content and high chlorophyll a/b ratio in leaves, low root-shoot ratio, and thinner leaves. In this study, germination of six native Asteraceae species was tested against 10%, 50%, and 100% of natural light in a greenhouse. Measurements of growth and reproduction were made in two species under the same light conditions. Shaded conditions decreased germinabilities of seeds in all species that were tested. Increased light conditions resulted in increased growth for both species. When exposed to shaded conditions, both species displayed several traits that are related with shade tolerance modifications such as little elongation of stems and petioles, higher specific leaf area, higher chlorophyll a/b ratio, reduced leaf area and root/shoot biomass, and fewer and thinner leaves. In summary, plants displayed unexpected strategies and a high resilience to grow and develop under shaded conditions.

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Rights

© 2019 Aline Rodrigues de Queiroz

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