摘要：The seasonal allocation of carbohydrates in water hyacinth was
evaluated to determine the physiological weak points in the life
cycle of this plant in three large, moderately polluted freshwater
canals north of the Nile Delta (Egypt). Monthly plant samples were
divided into laminae, petioles, stolons, stem-bases and roots to
determine the seasonal changes in water-soluble carbohydrates
(WSC), starch and total non-structural carbohydrates (TNC) for each
plant organ. Generally, water hyacinth allocated 2.2% of its total
biomass to stolons, 4.5% to stem-bases, 19.0% to roots, 21.1% to
laminae and 53.1% to petioles. The proportion of biomass allocated
to the root system (stolons, stem-bases and roots) decreased from
38.5% in April to 17.2% in July, while that of the shoot system (laminae
and petioles) increased from 61.5% to 82.8% during the same
period. Stem-bases were found to contain the highest concentrations
of WSC, starch and TNC throughout the water hyacinth’s life
cycle. Starch represented the greatest part of the TNC pool, surpassing
the concentration of WSC by 3.1- to 8.3-fold. The highest contents
(g/m2
) of WSC, starch and TNC were found in petioles. The
period in the seasonal cycle when water hyacinth is expected to be
most vulnerable to a control technique is when the carbohydrate
contents are at the lowest. Based on the present study, this would
be in April before complete mobilization of stored carbohydrates in
the stem-bases and stolons have allowed expansion of the leaf
material and the maximum growth rate.
关键词：Carbohydrate allocation ; floating macrophytes ; irrigation canals ; life history ; Nile Delta ; weed management
