Plant cultivars with high biomass production may have a high potential for being used in integrated water
treatment and plant production system. The highly productive hybrid Napier grass cultivar, Pennisetum
purpureum Pennisetum americanum cv. Pakchong1, may be a candidate species for being used in such
systems. We studied the effects of inorganic nitrogen form (NH4
+
, NH4NO3 or NO3
) on growth,
morphology, N uptake, water content and mineral allocation in this species under hydroponic conditions
at equimolar concentrations (500mmol N L1
). Generally, the N-form significantly affected growth,
biomass allocation and tissue nutrient and mineral composition of the plants. The hybrid Napier grass
grew better on NH4
+ compared to NO3
, and the plants supplied with NH4
+ contained three times more
chlorophylls than plants supplied with NO3
alone or NO3
combined with NH4
+
. The morphology of the
plants was, however, not affected by N source, exceptfor the shootto root ratio, which was lower in NH4
+
-
fed plants. The relative water content of the leaves was lowest in the NH4
+
-fed plants, but the
transpiration rate was not affected, indicating that NH4
+ nutrition and the associated low tissue
concentration of K had negative effects on the water use efficiency of the plants.
The study suggests that this hybrid Napier grass cultivar may be a new candidate species for use in
integrated water treatment and plant production systems.
ã 2