ffect of nutrient solution on the growth of P. helferi
The growth of P. helferi was studied using the DFT involving
nutrient solutions at five different EC levels from 0.4 mS/cm to
2.0 mS/cm. It was found that the differing EC levels significantly
affected the height and shoot number of P. helferi but did not
significantly affect the diameter of the shrubs (Table 6). The specimens
of P. helferi cultured at EC levels of 1.6 mS/cm had the greatest
growth with respect to their height with a significant increase in
the number of shoots (Table 6). After 6 wk, the specimens of
P. helferi cultivated at the EC level of 1.6 mS/cm began to grow better
than those under the other treatments. The height increased to be
7.47 ± 0.44 cm taller than the plants of other treatments experiment
which was significant until the experiment was terminated at
10 wk.
For the specimens of P. helferi grown at different levels of EC for
10 wk, there was a noticeable difference in the diameter of the
shrubs by the second week which resulted in different sizes among
different EC treatments in the second week. However, by the end of
the fourth week and throughout the remaining culture period,
there was no significant difference in the diameter of the shrubs.
A comparison of the average number of new shoots on the
P. helferi grown in nutrient solutions with differing EC levels found
that there were significantly more shoots on the plants grown at an
EC of 1.6 mS/cm at the start of week 8 than on any other plants.
Previous studies have reported that some species of aquatic
plants can grow well in EC conditions of 0.5e1.0 mS/cm for
example, Bolbitis heteroclita, one popular freshwater aquarium
plant, can grow well in sand culture without soil at an EC level of0.5 mS/cm (Wangwibulkit and Laohavisuti, 2009). Likewise, the
Java fern Microsorium pteropus can grow well when bound onto
wood and then cultured underwater in ponds at an EC level of
1.0 mS/cm (Wangwibulkit and Laohavisuti, 2006). Wangwibulkit
(2003) reported that culturing Cryptocoryne balansae at an EC
level of 0.5 mS/cm using the DFT provided the highest overall
production and Barclaya longifolia can grow well at an EC level of
0.75 mS/cm (Kasam, 2009). Some other aquatic plants, however,
have been reported to require more nutrients, such as Echinodorus
africanus, which requires an EC level of 2.0 mS/cm (Mitrnoi, 2007).
The nutrient requirement of plants depends on many factors and
variability exists among genera, species and even ages. In the current
trial, the most suitable nutrient solution that was tested for
P. helferi growth in a hydroponics system was found to be at an EC
level of 1.6 mS/cm, which provided the best growth for a 10 wk
culture period. The plants were observed to grow well, with height
(±SE) increasing to be 7.47 ± 0.44 cm taller than the plants of the
other treatments and the average number of shoots (±SE) increased
to 5.45 ± 0.47. However, the differing ECs did not significantly affect
the diameter of the shrubs.