EFFECT OF GAMMA RAYS, ABSCISIC ACID AND PUTRESCINE ON PRODUCTION OF WHEAT P.,LANTS MORE TOLERANT TO SALINITY: ~ A· GROWTH, CHEMICAL COMPOSITION, HORMONAL lSI TATUS, AND PRODUCTIVITY OF WHEAT PLANTS GROWN IN POTS UNDER SALINE CONDITIONS

Pot experiment were carrlec out during two successive seasons;
1999-2000 and 2000-2001, to investigate the effectiveness of the exogenous
applications of gamma rays, abscisic acid and putrescine in improving the
salinity tolerance of the salt-sensitive Giza 167 wheat cullivar aiming to
approach nearly similar tolerance and productivity of the untr~ated salt-
tolerant Sakha 8 cultivar, when both of them were irrigated with 15%, 30%
and 45% sea water, l.e. 4950, 9900 and 14850 ppm respectively, in addition
to the fresh (tap) water, I.e. 147 ppm in the control treatment. The obtained
data strongly confirmed the absolute superiority of the weekly spraying either
with 10IJM putrescine or 2 ppm ABA as well as the grains irradia ion with 15
KR gamma rays treatments, especially the first one, in inducing the highest
degree of the physioloqical tolerance to salinity in the treated sensitive Giza
167 cullivar plants which enables them to be adapted to the all applied levels
of salinity, and even could confirmed their superiority at least, up to 30% sea
water level in comparison with the salt-tolerant Sakha 8 cullivar plant under
the same conditions, This physiological tolerance to salinity brought about by
creating more negative osmotic potentials (Osmotic Adjustment) through the
accumulation of much more quantities of inorganic osmotica, t.e. • P. K+. Mg
'2 Ca+² and the highest K+'Na+ ratio as well as the lowest quan ities of Na'
and lowest Na+'Ca+² ratio in addition to considerable accumulation of organic
protective osrnolytes, l.e, s:..ga,s, pfoline, free amino acids and protein in their
growing tissues as well as the produced grains which greatly exceeded the all
other treatments especially both sensitive and tolerant untreated controls up
to 30% sea water level. This was accompanied with an ndogenous
hormonal status, induced by these three treatments, in favor 0 increasing
tolerance to salinity, i.e. the accumulation of cytokinin in the stressed roots
alongside the sugars, associated with another accumulation of I~, GA3 and
ABA in the stressed shoots, in addition to the lowest invertase activity in the
stressed leaves in favor of accumulation more non-reducing sugars,
Moreover, the most interesting feature of the obtained data is that, the
superiority of these treatments as regards growth, dry matter a cumulation,
chemical composition, endogenous hormonal status. invertase activity. was
reflected in much more pronounced degree on the productivity 0 the treated
plants, so much so that, it could highly significantly surpassed the
corresponding productivity of the all other treatments even t~at the salt-
tolerant untreated control up to 30% sea water level. Therefore, re obtained