Date of Award:

5-2024

Document Type:

Thesis

Degree Name:

Doctor of Philosophy (PhD)

Department:

Plants, Soils, and Climate

Committee Chair(s)

Youping Sun

Committee

Youping Sun

Committee

Amita Kaundal

Committee

Grant Cardon

Committee

Shital Poudyal

Committee

Shaun Bushman

Abstract

Soil salinity is a significant global issue that adversely impacts the growth and development of landscape plants. One of the effective strategies to prevent salinity damage to landscape plants is to cultivate species that are tolerant to the prevailing salinity levels. Salinity tolerance varies among plant species and cultivars. Therefore, this research aimed to investigate the salinity tolerance of nine landscape plants [Albizia julibrissin (mimosa tree), Arctostaphylos uva-ursi (kinnikinnick), Cercocarpus ledifolius (curl-leaf mountain mahogany), Cercocarpus montanus ‘Coy’ (alder-leaf mountain mahogany), Penstemon barbatus ‘Novapenblu’ (rock candy blue® penstemon), Penstemon strictus ‘Rocky Mountain’ (rocky mountain beardtongue), Punica granatum ‘Wonderful’ (pomegranate), Shepherdia ×utahensis ‘Torrey’ (hybrid buffaloberry), and Sophora japonica (Japanese pagoda tree)] and determine their responses to salinity stress. These landscape plants were tested for salinity tolerance in four separate greenhouse experiments. The effects of salinity levels ranging from electrical conductivity (EC) of 1.0 to 10.0 dS·m-1 were investigated. During the 8-week experiments, minimal to no foliar salt damage, such as leaf tip burn, leaf burn, or necrosis, was observed on A. julibrissin, P. granatum ‘Wonderful’, S. japonica, and S. ×utahensis ‘Torrey’. Whereas A. uva-ursi and C. montanus ‘Coy’ were dead when irrigated with saline solution at an EC of 10.0 dS·m-1. Two penstemon species had severe foliar salt damage or were dead when irrigated with saline solution at an EC of 10.0 dS·m-1. Elevated salinity reduced the shoot dry weight and photosynthesis of all plants. Furthermore, sodium (Na+) and chloride (Cl-) contents in plant tissues were affected by the elevated salinity levels. Chloride accumulation was greater in leaves than in stems or roots. However, Na+ accumulation was greater in roots compared to that in stems and leaves. Albizia julibrissin, P. granatum ‘Wonderful’, and S. japonica were able to maintain less Na+ content in their leaf tissue across all treatments. In conclusion, landscape plants exhibited different responses to salinity stress, A. julibrissin, S. japonica, S. ×utahensis ‘Torrey’, and P. granatum ‘Wonderful’ were relatively tolerant, while A. uva-ursi, C. montanus ‘Coy’, and two penstemons were relatively sensitive.

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