Two field experiments were carried out at the Experimental Farm of Cultivation
and Production of Medicinal and Aromatic Plants Dept. National Research Centre at
Giza, during two successive seasons, to study the effect of foliar application of two
tropane alkaloid precursors, phenylalanine (0, 100 and 200 ppm) and/or putrescine (0,
50 and 100 ppm) on some growth parameters and alkaloid contents of D. stramonium
and D. innoxia plants that originated from Bulgaria. Datura stramonium showed the
superiority of all growth parameters, except root weight at flowering stage, while at
fruiting stage. Datura innoxia showed visible increment of all growth parameters.
Application of phenylalanine 100 ppm+ putrescine 50 ppm was sufficient to accelerate
the growth parameters of D. stramonium at flowering and fruiting stages and D innoxia
at fruiting stage. At flowering stage, significant promotion in all growth parameters of
D. innoxia was observed due to foliar application of phenylalanine 100+ putrescine
100 ppm. D. stramonium with high level of phenylalanine and putrescine separately
significantly increased crude protein in leaves at flowering stage, while D. innoxia had
an opposite trend. The highest value of free amino acids in leaves at flowering stage
was obtained from D. stramonium plants treated with putrescine 50 ppm, while the
maximum percentage for D. innoxia was observed in plants treated with phenylalanine
100+ putrescine100 ppm. Hyoscine and hyoscyamine alkaloids were determined in
leaves and fruits at flowering and fruiting stages using HPLC. Most of phenylalanine
and putrescine treatments tended to increase hyoscine and hyoscyamine contents
(mg/g dry matter and mg/plant) of two Datura spp, throughout the growing seasons.
Foliar spraying with phenylalanine and putrescine connectively increased greatly
hyoscine, hyoscyamine and total alkaloids contents in Datura spp more than
individually ones, in most cases. Application of phenylalanine 100 + putrescine 50
ppm gave the highest values of hyoscyamine mg/plant, while treatment of
phenylalanine 100 + putrescine100 gave the highest levels of total alkaloids mg Iplant
in both Datura spp.