The aim of tne present work was to study the effectiveness of Argon-laser
irradiation ( 0.0.40.0.80.0, 120.0 and 160.0 minutes) in improving drought tolerance
of the micropropagated sugarcane plants grown under differenllevels of peG (0.0
4.0. 8.0, 12.0 and 16.0 % ). For this reason. experiments were conducted during 2001
and 2002 seasons. The obtained results clearly confirmed the absolute superiority of
lower dose (40 min.) of laser irradiation treatment. which significantly increases in the
growth parameters of sugarcane grown in vitro ( survival percentage. shoellet length.
No. of leaves I shootlet. No. of roots I planUet and fresh as well as dry weight of
shootlet ) and ex vitro ( culm length, culm diameter. No. of leaves I plant and shool
dry weight ) • yield components ( cane and sugar yield I plant) and juice quality
characters ( percentage of sucrose. purity. sugar recovery and total soluble solids)
over the untreated control treatment. Also. the sugarcane plantlets derived from shoot
tip treated with the lower dose ( 40 min. ) of laser rays were tolerant up to 8 % PEG
level and were able to continue their growth under glasshouse conditions till maturity
and cane production. The data also revealed that tolerance which was more
pronounced as a result of the lower rate of laser rays and was associated with high
accumUlation of much more quantities inorganic osrnonca.l.e. N. P • K. Mg and Ca as
well as lowest quantities of Na. in addition to considerable accumulation of organic
protective osmolytes ( sucrose. proline. amino acids and total soluble phenols).
photosynthetic pigments (carotenoids and chlorophylls ) and endogenous hormones
( IAA. GA3 and ABA ) in the sugsrcane g~own in vitro and ex vitro. Such
accumulation increased as the PEG level was Increased. Such behavior seems to
induce more ability for sugarcane plants to continue their growth till maturity and
production of cane even under 8 % PEG level. The obtained data suggested the
possibility of successful application of the Argon-laser rays to improve drought
tolerance of economic crops such as sugarcane.