INTERNATIONAL JOURNAL OF APPLIED AND EXPERIMENTAL BIOLOGY (ISSN PRINT: 2790-6523; ISSN ONLINE: 2790-6531) 2023, Vol. 2, NO. 1, 69-78. doi: 10.56612/ijaeb.v2i1.25 https://eminentscientists.com/ *CONTACT Khalid Hussain,  khalid.hussain@uog.edu.pk,  Department of Botany, University of Gujrat, Gujrat, Pakistan TO CITE THIS ARTICLE: Hussain, K., Diyyal, F.A., Nawaz, K., Arshad, N., Ali, U., Qurban, M. (2023). Promoting growth and morpho- physiological attributes in linseed (Linum usitatissimum L.) using indole acetic acid and gibberellic acid applied individually or jointly as foliar spray. International Journal of Applied and Experimental Biology 2(1): 69-78. © 2022 Society of Eminent Biological Scientists (SEBS), Pakistan Promoting growth and morpho-physiological attributes in linseed (Linum usitatissimum L.) using indole acetic acid and gibberellic acid applied individually or jointly as foliar spray Khalid Hussain 1 , Fatima Asghar Diyyal 1 , Khalid Nawaz 1 , Noshia Arshad 1 , Uswa Ali 1 , Mohammad Qurban 2 1 Department of Botany, University of Gujrat, Gujrat, Pakistan 2 Department of Botany, Khwaja Fareed University of Engineering and Information Technology, Rahim Yar Khan, Pakistan Abstract Gibberellic acid (GA 3 ) and indole-3-acetic acid (IAA) are commercially and scientifically important due to their promising impacts on growth, quantity and quality of most crops. The current work intended to observe the effect of foliar applications of plant growth regulators (IAA and GA 3 ) on linseed morpho-biochemical attributes and key antioxidants. Indole-3-acetic acid showed more beneficial effects on growth and antioxidant activities than those by GA 3 . Root length, shoot length, photosynthetic rate, root fresh weight, and N were respectively 38%, 25%, 38%, 60%, and 1.26% higher with combined treatments of IAA+GA 3 than those of the control plants at the vegetative stage. The effect of IAA was highly significant on N percentage, total protein contents and fibre percentage in linseed at both seedling and vegetative stages. Overall, the nutritional value of linseed was boosted by both PGRs, i.e., GA 3 and IAA. Furthermore, it is recommended that IAA, GA 3 and their combined applications can be used to enhance the quality of cereal crops. HANDLING EDITOR Muhammad Ashraf ARTICLE HISTORY Received: 23 Feb, 2022 Accepted: 15 Nov, 2022 Published: 30 Dec, 2022 KEYWORDS Growth enhancement; IAA; GA 3 ; Antioxidant; Proteins Introduction Linseed (Linum usitatissimum L.) is a potential source of quality oil and fibres. Humans have been growing this plant for years (Vaisey-Genser and Morris, 2003). The overall production of linseed in Pakistan is 2,779 tonnes utilizing 4,018 ha for its cultivation (Anon, 2011). Linseed usually contains 5% mucilage, also called viscous fibre and lignin (Muir and Westcott, 2003). Linseed normally contains 40- 50% oil and meal, 23-34% protein and 4% ash, but this composition may vary from cultivar to cultivar as well as under varying environmental conditions (Muir and Westcott, 2003). Linseed crop capacity is not adequately utilized due to various limiting factors for its cultivation, such as an inadequate supply of nutrients and accumulation of nutrients (Oad et al., 2004). Plant growth, development and differentiation are regulated by growth hormones either by inhibition or improvement in a variety of metabolic processes (Naeem et al., 2004). Of different plant hormones reported in the literature, indole acetic acid plays a critical role in cell division and elongation, as well as in several other physiological functions involved in plant growth and development (Aloni et al., 2006; Tian et al., 2014; Zhang et al., 2022). It is believed that it plays a significant role in the regulation of stress tolerance in plants subjected to various stressful cues. Similarly, gibberellic acid is known to boost cell division and elongation, promoting plant height (Shan et al., 2021). However, like IAA, gibberellic acid can also play an essential role in improving stress tolerance in plants by triggering a myriad of metabolic