Roots are important for plant survival and growth because of their key functions in water and nutrient uptake, anchoring and support of the plant, symbiosis with beneficial microorganisms, and root-soil interface in relation to environmental stresses, such as drought and salinity. The continuous integration of intrinsic and extrinsic factors related to environmental conditions and soil water and nutrient status leads to the adaptation of root system architecture (RSA), the spatial configuration of a root system in the soil, for maximal plant growth and survival. RSA and its plasticity are therefore vital and dynamic factors controlling agricultural productivity. Although root-related research for crop improvement lagged far behind vegetative and reproductive -related research it was proposed that roots are the hidden half of crop yield and a key factor potentially to a second Green Revolution. Thus, it has triggered massive efforts to understand root traits contributing to crop productivity. Plant hormones such as auxin and abscisic acid (ABA) play key roles in root growth and development The plant steroidal hormone, brassinosteroid (BR), controls root growth and confers tolerance to environmental stresses such as salinity and drought. However, the role of BR in regulating RSA in response to stress, and how BR-mediated RSA is correlated to plant performance under stress, has not yet been studied. This PhD project was conducted to determine 1) the effects of BR on RSA of untreated and BR-treated wild type (WT) and BR-deficient and signalling Arabidopsis thaliana mutant seedlings under no stress and under either drought- or salt- stress conditions, and to correlate these to physiological and growth response (Chapter 3), 2) the relationship of the BR pathway with the signalling molecules, such as reactive oxygen species (ROS), nitric oxide (NO) and Ca2+ (Chapter 4), and 3) the interactions of BR pathway with the pathways involved in salt stress responses (Chapter 5), and 4) the changes in global gene expression in seedling roots under a stress condition where BR effect was most pronounced (Chapter 6). The results of the entire study indicate that BR-mediates changes in RSA of Arabidopsis seedling under salt and dehydration stress conditions are concomitant with robust stress responses and better growth of the seedlings under these conditions. BR confers salinity tolerance by interacting with the SOS pathway, changing the levels of signaling molecules ROS, NO and Ca2+ in root cells, and impacting gene expression changes that are likely to confer salt stress tolerance.
Date of Award | 2022 |
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Original language | English |
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Awarding Institution | - Western Sydney University
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Supervisor | Priti Krishna (Supervisor) |
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- Brassinosteroids
- Roots (Botany) -- Physiology
- Arabidopsis thaliana -- Effect of chemicals on
- Arabidopsis thaliana -- Effect of stress on
Effect of brassinosteroid on root system architecture of Arabidopsis thaliana L. under salt and dehydration stresses
Chakma, S. (Author). 2022
Western Sydney University thesis: Doctoral thesis