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The effect of 2 growth regulators, betaine and thiourea, was examined to learn the extent to which they can alleviate salinity-induced dormancy of wheat seeds. Germination velocity (as measured by Timson index) progressively decreased with increasing salinity, while thiourea and betaine, alone or in combination, elevated the germination velocity of wheat seeds. | Turk J Bot 30 (2006) 321-330 © TÜB‹TAK Research Article Alleviation of Salinity-Induced Dormancy by Growth Regulators in Wheat Seeds Zamin Shaheed SIDDIQUI*, Syed Shahid SHAUKAT, Arif-Uz-ZAMAN Stress Physiology & Environmental Pollution Lab., Department of Botany, University of Karachi, Karachi, 75270 - PAKISTAN Received: 13.06.2005 Accepted: 25.04.2006 Abstract: The effect of 2 growth regulators, betaine and thiourea, was examined to learn the extent to which they can alleviate salinity-induced dormancy of wheat seeds. Germination velocity (as measured by Timson index) progressively decreased with increasing salinity, while thiourea and betaine, alone or in combination, elevated the germination velocity of wheat seeds. Timson index showed significant improvement in germination velocity when thiourea was used at 225 mM NaCl. Likewise, the adverse effect of salinity on growth parameters, like root and shoot lengths and fresh and dry weights, was also alleviated considerably when growth regulators were added. The application of growth regulators in combination with NaCl resulted in increased level of reducing sugars in the embryo and a decrease in the endosperm coupled with enhanced amylase activity, suggesting significant recovery in the mobilization rate of soluble sugars from endosperm to embryo. Thiourea was more effective in the mobilization process compared to betaine. Significance of growth regulators in alleviating the salt stress in crop plants is discussed. Key Words: Salinity, thiourea, betaine, germination velocity, reducing sugars Introduction Growth promoters such as GA and kinetin, regulators, i.e., nitrate and thiourea, and compatible osmotica, like proline and betaine, are well-known to alleviate salinityinduced dormancy in wild plants (Plyler & Proseus, 1996; Yoshiba et al., 1997; Khan et al., 1999; Khan & Ungar, 2001). Growth regulators like nitrate, nitrite, and thiourea often stimulate germination (Esashi et al., 1979; Aldosaro et al., .
