Page 2 Plant-Bacteria Interactions Edited by Iqbal Ahmad, John ...

inorganic industrial effluents containing metal ions [55,76,81,82,87]. Being highly
adaptive to severe conditions, free-floating and capable of rapid vegetative reproduction
and surviving in diverse habitats, water hyacinth is well distributed throughout
the world. With a maximum productivity as high as 54.4 g of dry weight m 2
day 1 [55,87], plants grow rapidly during warm season and can cover 15% more
surface area every day. Optimum conditions for growth are temperatures ranging
between 26 and 35 C, pH 6–7 and 240 000 lx h [87,107,108].
15.4.4
Environmental Impact
Water hyacinth grows so abundantly in rivers and other navigable waters that it
obstructs the passage of ships and water flow in irrigation channels and hinders
hydroelectric power generation. Water hyacinth has devastating impacts also on
fresh water ecosystems in various ways [55,87,109]. The extensive growth of water
hyacinth depletes oxygen completely, as the rate of organic matter production is so
high that large amounts of dead organic matter accumulates in the water. The
decomposing organic matter depletes oxygen and hence kills biota and generates
obnoxious odors [55,109]. Decomposition also releases free CO2 that reacts with
water to produce H 2CO 3, which decreases the pH of water [55,87]. Excessive growth
of water hyacinth causes the reduction of light penetration into water bodies, which
leads to the reduction of water temperature and affects the growth of phytoplanton
[55].
15.4.5
Management of Water Hyacinth
15.4 Biology of Water Hyacinthj293
Because of its high reproductive rate, ability to adapt to adverse environments and
free-floating nature, it is difficult to restrict the growth of water hyacinth
[55,87,109,110]. Numerous studies have been conducted to develop suitable management
techniques to control its prolific growth [87]. In a conference organized by
the Common Wealth Council, various control measures involving chemical, biological
and mechanical devices including using pesticides, herbivorous aquatic mammals
and fish, insects and microbial plant pathogens have been suggested and
practiced [111–113]. Mechanical removal has been reported as the most complete
and effective method to control water hyacinth, but the process is relatively slow,
expensive and labor-intensive [87,110]. Another method to control growth of water
hyacinth is economic utilization. Studies have reported that water hyacinth has
potential as an effective absorber of organic and inorganic water pollutants
[55,87]. Extensive studies have been conducted on the possibility of using water
hyacinth for secondary and tertiary treatment of sewage and various industrial
effluents [55].
Water hyacinth contains about 26% crude protein, 26% fiber, 17% ash and 8%
available carbohydrate on a dry weight basis [87]. Because of its high protein content,
water hyacinth can be considered as a protein source for nonruminant animals and