Doctor Fikadu Biru


Graduated PhD 2023

Thesis Title

The effects of atmospheric CO2 on silicon accumulation, plant defensive traits and herbivore attack

Research Project

Fikadu BiruSilicon (Si) is the second most abundant element after oxygen in the earth's crust. Si is one of the plant mineral nutrients captured from the soil in the form of solid silica (SO2) but is initially absorbed and transported in the form of monosilicic acid [(HSO)4] which is deposited in the plant tissues in the form of phytoliths. Si deposition in plant tissue has a wide range of roles in plant defence against multiple environmental stresses. For example, Si accumulation by the plants confers plant defences against insect herbivores.

Further, Si-rich grasses expanded greatly during the Miocene which were associated with Si phytoliths that potentially played a role in resisting the effects of co-evolving herbivores. With the high metabolic costs of several defensive chemicals, some plant species potentially substitute Si for carbon-based defences under low atmospheric carbon dioxide concentrations during Miocene when carbon was less abundant. This idea is speculative, although it is true that the contrary occurs (lower Si uptake) in higher CO2. My PhD project aims to address how climate changes, particularly atmospheric CO2 alter Si accumulation in a model grass Brachyodium distachyon and the consequences for insect herbivory.

Given, the growing importance of atmospheric CO2 impacts on plant defences, it is particularly novel to study Si uptake under lower CO2 concentration since the majority of the research, which only amounts to a handful of studies, has focused on rising CO2 concentrations and Si uptake.

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Biru FN, Cazzonelli CI, Elbaum R, Johnson SN, (2022) 'Contrasting impacts of herbivore induction and elevated atmospheric CO2 on silicon defences and consequences for subsequent herbivores', Entomologia Experimentalis et Applicata vol.170, no.8, pp 681-688

Johnson SN, Cibils-Stewart X, Waterman JM, Biru FN, Rowe RC, Hartley SE, (2022) 'Elevated atmospheric CO 2 changes defence allocation in wheat but herbivore resistance persists', Proceedings of the Royal Society B: Biological Sciences, vol.289, no.1969, Article no.20212536

Biru FN, Islam T, Cibils-Stewart X, Cazzonelli CI, Elbaum R, Johnson SN, (2021) 'Anti-herbivore silicon defences in a model grass are greatest under Miocene levels of atmospheric CO2', Global Change Biology, vol.27, no.12, pp 2959-2969

Biru, FN, Cazzonelli CI, Elbaum R, Johnson SN, (2020) ‘Contrasting effects of Miocene and Anthropocene levels of atmospheric CO2 on silicon accumulation in a model grass’, Biology Letters, vol 16, no. 20200608


Associate Professor Scott N. Johnson, Dr Christopher I. Cazzonelli, and Professor Rivka Elbaum