EFFECT OF NITROGEN SOURCES AND GIBBERELLIC ACID RATES ON GROWTH AND CHEMICAL COMPOSITION OF CYCAS PLANTS (Cycas revoluta THUMB.)

The present work was designed to study the effect of different nitrogen sources
(ammonium nitrate, ammonium sulphate and urea) and gibberellic acid rates (0, 250
and 500 p.p.m. /plant) on growth of Cycas revoluta seedlings, that were one-year-old,
during two experiments of 2003 and 2004 in the green-house at Antoriiades Branch,
Hon. Res. Inst., A.R.C. Alexandria. Egypt.
The results indicated that ammonium nitrate significantly increased most of the
studied vegetative growth characteristics (number of leaves? plant, leaf length , leaflet
length and number/ leaf, fresh and dry weights of leaves? plant, fresh weight of stem
and its circumference, leaves content of total chiorophylls and nitrogen percent of dry
Leaves), compared to ammonium sulphate and urea.
Gibberellic acid had insignificant effects on most characteristics of vegetative growth
while reduced the others.
In general, using ammonium nitrate (33.5%) as source of nitrogen at the rate of
1.5g / plant monthly during the growth of Cycas revoluta seedlings was the best
treatment without using GA3 in the green-house.