Effects of high light intensity and desiccation stress on moss species.
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Date
2021
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Abstract
Bryophytes are desiccant tolerant non-vascular plants, capable of growing and surviving in
extreme conditions. They are divided into three groups: liverworts, hornworts, and mosses.
Most mosses grow in shady and moist environments, although some formpart of arid soil crusts
where they protect soil from erosion. The moss flora of the Afromontane vegetation around
Pietermaritzburg is dominated by two acrocarpous mosses, Atrichum androgynum, and
Dicranella subsubulata. A. androgynum tends to grow in wetter, more shaded habitats and is a
rather delicate species, while D. subsubulata grow in open, drier habitats and is more robust.
Rarely, the species grow together, for example at the transition of a shaded indigenous
woodland to plantations. We hypothesized that the more robust species has higher stress
tolerance and has largely constitutive stress tolerance mechanisms. By contrast, we
hypothesized that the more delicate species is less tolerant and may have inducible tolerance
mechanisms. In the present study, desiccation tolerance and tolerance to high light stress were
investigated in A. androgynum and D. subsubulata. Results confirmed that D. subsubulata was
more tolerant of high light stress than A. androgynum. Exposure to moderate light intensities
did not increase tolerance to subsequent high light stress in either species. Similarly, D.
subsubulata was more desiccation tolerant than A. androgynum. Not consistent with our
original hypothesis, mild desiccation, and treatment ABA-induced tolerance to desiccation in
both species. Furthermore, detailed studies of the antioxidant enzyme peroxidase showed that
enzyme activity was induced during slow drying in both D. subsubulata than A. androgynum.
It appears that inducible tolerance mechanisms are present in both species. The work
presented here represents a contribution to the autecology of two important mosses in the
KwaZulu-Natal midlands Afromontane vegetation.
Description
Masters Degree. University of KwaZulu-Natal, Pietermaritzburg.