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Victoria University of Wellington (2020)

Evaluating the functional role of betacyanin in salinity tolerance of Horokaka (Disphyma australe)

Whyte Alexandra

Titre : Evaluating the functional role of betacyanin in salinity tolerance of Horokaka (Disphyma australe)

Auteur : Whyte Alexandra

Université de soutenance : Victoria University of Wellington (NZ)

Grade : Master of Science in Ecology and Biodiversity 2020

Résumé partiel
Yield loss in agriculture due saline soils is a growing problem in arid and semi-arid regions as traditional crop species are inherently sensitive to salinity in the root zone. In the face of diminishing fresh water resources it is necessary to explore the traits which allow naturally salt tolerant species to exploit high saline environments. In the hope of transferring these traits via genetic modification to traditional crop species, or utilising these species as niche crops in their own right. While a majority of plants appear green, red pigmented plants are commonly associated with marginal environments. In these leaves anthocyanins or less commonly betalains are responsible for leaf reddening. The betalains are small class of tyrosine derived chromo alkaloids found in the core Caryophyllales and in some Basidiomycetes. There are two structural groups : the red/violet betacyanins and the yellow/orange betaxanthins. Due to this distribution pattern, betalain pigments are thought to function in salinity stress tolerance. However, minimal research has been conducted to support this salinity tolerance hypothesis due to a lack of an appropriate model species. Horokaka (Disphyma australe) exhibits colour dimorphism among populations, green and red morphs grow contiguously in coastal environments where the frequency of red morphs positively correlates with increased substrate salinity. Betacyanins have previously been implicated in serving a photo protective for D. australe. In dimorphic populations D. australe along the south Wellington coastline, the red morph has been shown to be more tolerant to the combination of high light and salinity, as measured by higher CO2 assimilation rates, reduced inhibition of PSII and enhanced water use efficiency relative to the green morph. In these studies, betacyanin production in the red morphs was shown to depend on duel exposure to both salinity and high light, however the green morph was unable to produce betacyanin under the same conditions (Jain & Gould, 2015)

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