Thi-; study was conducted a\ the Department of Ornamental Horticultur~. Faculty of Agriculture Cairo University. Giza, and the Fann 01 Medicinal and AromatiC
Plants. Faculty of Pharmacy, Cairo University. Giza. during the two sl)CcesSiV~
seasoos of 1997 ana 1996. with tl1e aim of investigating the effect of irrigatio~
intervals and chemical NPI< fertilization on the chemical composition and production
of active constituents in senna (Cassia aculi'1Olia. Delile) plants. Cassia aculifolia were irrigated every 1. :2 or 3 weeks. and were supplied with
chemical NPK fertilization :.Jsing combinations 01 N al the rates of 0, 25. 50 or 75
kglfed. (No. N1, N2 and N3, respecfively), P,Os at 0, 25 or 50 kg/fed. (Po. Pl and pzi
respectively) and I< at 25 kglfed. (1<1). In addition, plants receiving no Chemica
fertilization (NoPo~) were used as the centrol.! The percentages of sennoside B in the leaves and pods were generally
higher than those of sennoside A. and the percentages of both sennosldes were
higher in the pods than in the leaves. Irrigation every 3 weeks gave Ihe highest means
for ~ercentages of tolal sennosides in leaves and pods, sennosides yielQ rrom
leaves/plant. and percentages ot sen nos ides A and B in glycosides extracted from
leaves and pods, whereas irrigation every 2 weeks gave the highest sennosldes yield
trom pods/plant and the highest total sennostdes yield (from leaves + podr.)lplant, 8S
well as the highest percentages 01 N, P and I< in the leaves and stems. On the other
hand, the highest contents of leaf pigmenls (chlorophyll a, band carotenoids) were
obtained with weekly irrigation, In seneral, the difterent fertilization treatments
decreased the total percentages of sennosldes, as well as the percentages of
sennosides A and 8 in leaves and pees, but increased the sennosides yield from
leaves/plant and podslptant (with NZP2K1 giving the highest values). the leaf pigments
con lent , as well as the N, Pend K contents in leaves and stems (with NJP₂K1 giving
the highest values for these characteristics). For each of Ihe different characteristics
that were studi~. lhe highesl values wele obtained when the best irrigation interval
for the studied characteristic was combined wilh using the best fertilization treatment.