Abstract
Phytohormones play key roles in many aspects of plant growth and development, as well as in resistance to abiotic stresses. The presence of heavy metal limits phytohormone endogenous level; however, the application of brassinosteroids (BRs) restores phytohormone homeostasis and reduces unfavorable consequences of heavy metal on plant growth. Therefore, the aim of this study was to (1) broaden previously published analyses/findings to study the effect of 24-epibrassinolide (EBL) and/or lead (Pb) on Acutodesmus obliquus phytohormone level after 5 days of cultivation using LC-QToF-MS quantification technique and (2) extend the total amount of quantified phytohormones in A. obliquus. The study confirmed that exogenous EBL increased the contents of gibberellin A3 (GA3), auxins (AXs) (indole-3-acetic acid, phenylacetic acid), BRs brassinolide, 24-epibrassinolide (EBL), 28-homobrassinolide, castasterone, 24-epicastasterone, typhasterol, cathasterone, 6-deoxotyphasterol, as well as different types of cytokinins (CKs): free bases, ribosides, and conjugates (N- and O-glucosides). On the other hand, treatment with Pb had an opposite effect on BRs, GA3, AXs, and free bases, as well as ribosides of CKs. The abscisic acid (ABA) level decreased under EBL treatment but increased in response to Pb stress. The level of N-glucosides, as well as O-glucosides of CKs, also significantly increased in response to Pb alone. Interestingly, the co-application of EBL and Pb led to an increase in BRs, GA3, AXs, and CKs content in the algae. Principal component analysis revealed that based on treatments, increase of GA3, BRs, and AXs was found to be in the following order: 1 μM EBL > 0.01 μM Pb + 1 μM EBL > 500 μM Pb + 1 μM EBL > control > 0.01 μM Pb > 500 μM Pb. Moreover, very strong significant linear relations between almost all studied AXs and BRs were noted. Summarizing, this research did not only allow to detect the occurrence of ABA, GA3, AXs, BRs, and CKs in A. obliquus for the first time but also to study the combined action of EBL and Pb, as well as compare it with treatment alone.
Highlights
Plant hormones are naturally occurring organic compounds that play a significant role in most physiological processes of plants, such as growth and stress responses
The present study reports the occurrence of abscisic acid (ABA), gibberellin A3 (GA3), AXs (IAA; phenylacetic acid, PAA), different types of BRs: 7oxalactone type (BL, EBL, HBL), 6-oxo type (CS, ECS, TY, cathasterone (CT)), 6-deoxo type (6-deoxytyphasterol, dTY) as well as different types of CKs: free bases, N-glucosides, O-glucosides (cZOG, cZROG, tZOG, tZROG, dihydrozeatin-O-glucoside (DHZOG)), and ribosides in A. obliquus (Table 1)
In terms of quantity, AXs dominated in green alga (25.93 pmol PAA g−1 fresh weight), slightly lower content was detected for CKs (7.96 pmol cZ g−1 fresh weight), ABA (5 pmol g−1 fresh weight), BRs (3.25 pmol CT g−1 fresh weight), and GA3 (1.76 pmol g−1 fresh weight)
Summary
Plant hormones are naturally occurring organic compounds that play a significant role in most physiological processes of plants, such as growth and stress responses The level of endogenous phytohormone is the result of complex metabolic processes, such as biosynthesis, conjugation, degradation, and transport. These processes are subject to coordinated regulation, ensuring hormonal homeostasis, essential for the proper functioning of the plant.
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
