The current investigation was carried out during the two successive seasons
of 1998/1999 and 1999/2000 in order to enhancement seed germination and produce
vigorous transplants inS panish mahogany by different methods of application with
GA3. Therefore , seeds of Spanish mahogany were soaked in different concentrations
of GAJ ( 0.0,50 , 100 ,200 and 400 ppm) or plants, three months old, were sprayed
with 25 , 50 and 100 ppm GAJ. The percentage of seed germination , vegetative growth characters , photosynthetic pigments , total sugars , endogenous phytohormones and stem anatomy of Swietenia mahogani (L.) Jacq.as affected by GAJ treatments were
'investigated . The obtained results revealed that all seed soaking treatments
increased the percentage of seed germination in both studied seasons and maximum
significant increase was recorded at 400 ppm GAJ which in turn being statistically
indifferent with that of 200 ppm GAJ . Also , it was found that different methods of GAJ
application had, in general, beneficial effects on all studied characters of vegetative
growth ( plant height, total leaf area/plant and fresh and dry weights of shoot 1 plant) .
The maximum beneficial effect was 0 btained at foliar application with 50 ppm GAJ
which induced vigorous growth in both studied seasons . It is realized that seed
soaking treatments as well as foliar application treatments with GAJ increased
chloroplast pigments, total sugars and endogenous 1M and GAJ in leaves of Spanish
mahogany , 10 months old ,. Whereas , endogenous ABA was decreased in this
respect. Worthy to note that among seed soaking treatments, 400 ppm GAJ was the
promising concentration . While , among foliar application treatments , 50 ppm GAJ
was the best concentration in this concern . Moreover , it was found that foliar
application with 50 ppm GAJ caused considerable thickness of main stem by
increasing the thickness of all included tissues. Thickness of periderm , cortex ,
phloem tissue and xylem tissue as well as pith diameter were increased in treated
plants.