Abstract
Salinity stress is an emerging abiotic stress that effects the plant growth as well as development. Based upon this emerging problematic threat an experiment was conducted to study the morpho-physiological traits of cotton to find out the effect of foliar application of silicon (T
0
= controlled, T
1
= 200PPM, T
2
= 400 PPM, and T
3
= 600 PPM) on cotton seedlings under salinity stress (S
0
= controlled and S
1
= 500 PPM). Four varieties of upland cotton IUB-13, CIM-707, FH-900, and IUB-4 were sown in polythene bags in wire house of Department of Plant Breeding and Genetics, Faculty of Agriculture and Environment, The Islamia University of Bahawalpur in 2020. Results revealed that the highest values of height of plant (17.50 cm), number of leaf (6.04) and number of nodes (4.61) were recorded in IUB-4 than all others varieties of cotton. Highest value maximum chlorophyll content (13.90 mg/g), in FH-900, stomatal conductance (119.58 mmol H2O m
− 2
s
− 1
) in CIM-707 and proline Content (1.31 µ g g
− 1
FW) in IUB-13 were recorded. Maximum APX (13.506 Units min
− 1
g
− 1
FW), POD (0.4104 Units min
− 1
g
− 1
FW, SOD (207.49 Units min
− 1
g
− 1
FW) and CAT (1.1792 Units min
− 1
g
− 1
FW) were recorded in FH-900, IUB-13 and IUB-4 respectively in cotton with foliar applied Si. The interaction between varieties showed that some traits are positively correlate whereas some are negatively correlate like when the CAT, PC, and POD were increased, APX showed a positive and substantial effect. Similarly, APX showed a non-significant increase in the levels of CC, NL, and NN. When the APX, CAT, CC, and PC were elevated under stress, the SC showed a negative and significant effect. For NL, PH, and POD, however, there was a negative and negligible connection with stomatal conductance. For APX, CC, NN, PC, PH, and SC, there was a positive and insignificant connection with SOD. For CC, NL, and NN, the PH had a positive and very significant effect. POD had a positive and significant effect on APX and CAT as well. Foliar silicon helpful for enhancing salt tolerance in cotton and improving its growth and antioxidant activities.