Author(s):

Dr. P Madhana Kumara and S Eswaramoorthy

Abstract: An experiment was conducted to find out the ability to challenge salinity stress in aggregatum onion (<em>Allium cepa var aggregatum</em>) using plant growth regulators. The experiment was carried out at Department of Horticulture, Faculty of Agriculture, Annamalai University. The bulbs of Gnanamedu local variety were selected to undergo the physiological performance for yield improvement under salinity. To fix the critical threshold level of salinity and to understand the mechanism of stress with the concentration of NaCl from 10 mm to 70 mm. Among the various NaCl concentration (10-70mM), concentration beyond 50mM showed more than 75% reduction in dry matter. Thus 50mM of NaCl concentration was identified as the threshold level upto which management strategies would work to restore the elastic strain. Then the seedlings were treated with plant growth regulators viz. Hexaconazole, Triadimefon, Propiconazole and Tetraconazole for mitigating the salinity stress. The data on various physiological attributes indicated that the reduction was brought out by the ionic, osmotic and secondary stresses. The activity of sodium and potassium got changed and enhanced the production of proline, increased the membrane stability and reduced electron leakage. Further increased proline content indicates the role of plant growth regulators in osmoregulation and maintenance of cell integrity. The result on various biometric traits reveals that increased yield was mainly contributed by increased number of bulbs, bulb length, bulb diameter and individual bulb weight. Thus, it is concluded that under salinity stress within the threshold limit, exogenous application of hexaconzole @ 5 ml per lit would mitigate the salinity stress to about 80 per cent.

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