Author Identifiers

Melissa Karlinski
ORCID: 0000-0003-0362-5447

Date of Award

2019

Degree Type

Thesis

Degree Name

Master of Science (Biological Sciences)

School

School of Science

First Advisor

Professor Ray Froend

Second Advisor

Dr Paul Drake

Field of Research Code

010900, 010903

Abstract

Fluctuating environmental conditions place plants at risk of mortality if they cannot adapt, particularly to warmer temperatures and drier environments. Plants are known to modify their morphology, physiology and anatomy to thrive under these conditions, and xylem anatomy and hydraulic architecture are common traits studied to understand plant adaptations and responses to changeable water availability. However, little is known about the changes to the hydraulic architecture of groundwater dependent plants during their early establishment in water-limited environments. By exposing young seedlings of two Banksia species to contrasting groundwater availability treatments in a glasshouse experiment, it was possible to analyse the xylem vessel traits (vessel diameter (Vd), maximum vessel diameter (Dmax), vessel density (Dv) and vessel length (VL)) in root and stem tissue samples using ImageJ software. Analysis of vessel traits identified significant vascular tapering in both Banksia attenuata and B. littoralis, i.e. a low density of large diameter vessels found in roots, and a higher density of small diameter vessels found in the stem. Vessel traits of B. attenuata and B. littoralis seedlings with access to an artificial water table did not differ significantly to those with access to only unsaturated soil. This lack of significant difference was surprising as studies have shown variation in xylem anatomy of plants exposed to contrasting water availabilities, commonly referred to as the hydraulic efficiency and safety trade-off theory. However, the traits did vary between the two species, with significantly larger mean Vd and Dv in B. attenuata seedling roots, and significantly higher mean Dv in B. littoralis seedling roots. VL also differed, with B. attenuata having significantly longer vessels than B. littoralis. These differences may relate to the contrasting habitat requirements of the chosen species. B. attenuata occurs across varying gradients in depth to groundwater, while B. littoralis is found in low-lying swampy areas. This could suggest that B. attenuata may be more ‘flexible’ in its xylem development, whereas B. littoralis develops a more rigid anatomy, affording protection in case of disconnection from groundwater. The findings from this study provide a better insight into how the xylem anatomy of groundwater-dependent species varies in relation to groundwater availability, and how and why species of the same genus may develop significantly different vessel traits.

Available for download on Thursday, June 24, 2021

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