Overview of Wolffia arrhiza (L.) Horkel ex Wimm.
Wolffia arrhiza, also known as rootless duckweed or spotless watermeal, is a floating aquatic plant and the smallest flowering plant in the world. It belongs to the duckweed family (Lemnaceae) and is found in many parts of the world, including North America, Europe, and Asia.
General Appearance of Wolffia arrhiza (L.) Horkel ex Wimm.
The plant is tiny and measures about 1-3mm in length and 0.5-1.5 mm in width. It is oval shaped, flattened, and has a green color. Wolffia arrhiza does not have roots but has a small cavity on its underside that helps it to float on the water surface. The plant reproduces vegetatively and can form dense floating mats on the water surface.
Common Names of Wolffia arrhiza (L.) Horkel ex Wimm.
Wolffia arrhiza has several common names, including rootless duckweed, spotless watermeal, and lesser duckweed. In some areas, it is also referred to as simply duckweed.
Uses of Wolffia arrhiza (L.) Horkel ex Wimm.
Wolffia arrhiza has various uses, including as food for fish and livestock. It is rich in protein and can be used as a source of food for humans. The plant is also used in wastewater treatment as it can absorb certain pollutants from the water.
Light Requirements
The plant Wolffia arrhiza grows best in bright light. It requires at least 4-6 hours of direct sunlight per day to thrive. However, it can also tolerate moderate shades to some extent. When grown indoors, it is recommended to place the plant near a south-facing window to provide sufficient sunlight.
Temperature Requirements
The ideal temperature for the growth of Wolffia arrhiza is between 20-30°C (68-86°F). This plant does not tolerate frost or extreme temperatures. In cold regions, the plant can be grown in a greenhouse or indoors in a warm, humid environment.
Soil Requirements
Wolffia arrhiza does not require soil as it is an aquatic plant. It prefers to grow in stagnant, still water bodies such as ponds, lakes, and slow-moving streams. The water should be free from pollutants, and the pH level should be between 6.5-7.5. The plant can grow in different types of water such as freshwater, brackish, or saline water.
Cultivation
The plant Wolffia arrhiza (L.) Horkel ex Wimm. is a type of duckweed and is known for its aquatic nature. It can grow and thrive in slow-moving water with a depth ranging from 3-20 cm and a pH range of 6-9. The plant can quickly multiply, covering the entire surface of the water body if not checked in time. The ideal temperature for the plant's growth ranges between 24-30°C.
Watering Needs
Being an aquatic plant, the Wolffia arrhiza (L.) Horkel ex Wimm. plant relies on water for its survival. The plant gets all its nutrients from the water-body where it grows. Therefore, there is no need to water it externally.
Fertilization
The Wolffia arrhiza (L.) Horkel ex Wimm. plant takes all its nutrients from the water where it grows. In case of insufficient nutrients in the water, the plant might require fertilizing. Fertilizers rich in nitrogen and phosphorus are ideal for the growth of the plant. Doses of the fertilizer can be periodically added to the water source to enhance growth.
Pruning
Pruning is not necessary for Wolffia arrhiza (L.) Horkel ex Wimm. plants. The plant can grow and propagate without any trimming. However, if there is excessive growth to the extent that it is blocking sunlight or oxygen for other aquatic plants and organisms, the plant can be thinned out. The process involves skimming off the excess plant material, making sure not to remove all the plants as the remaining ones will propagate and grow back to fill the space.
Propagation methods of Wolffia arrhiza (L.) Horkel ex Wimm.
Propagation is essential for plant growth and development. Wolffia arrhiza can reproduce itself via asexual and sexual reproduction methods.
Asexual propagation
Wolffia arrhiza produces new plants through vegetative reproduction. The plant produces buds, which can develop into new plant individuals. The buds form on the mother plant's body and are capable of floating away and forming independent plants, or they might remain attached to the mother plant and create small colonies or chains. Because each plant is a hermaphrodite, each offspringed Wolffia may produce other offspring for propagation in similar ways, which speeds up the formation of large colonies.
Sexual propagation
Wolffia arrhiza also flowers and produces seeds. The tiny white flowers are hermaphroditic and located inside a small pouch. They open for less than a day, and the tight space keeps them from being pollinated by their own flowers. Insects and wind pollinate Wolffia arrhiza flowers.
Two ovules in the Wolffia flower penetrate the ovaries. The embryos are then enclosed in protective covers, which form seeds. However, sexual propagation is less effective than asexual propagation in the case of Wolffia arrhiza.
Propagation of Wolffia arrhiza helps it to colonize underwater environments quickly. The plant's small size and ability to reproduce rapidly through asexual propagation minimize the pressure to produce flowers and seeds. Consequently, the plant usually relies on vegetative or asexual propagation methods for survival and proliferation.
Disease Management
Wolffia arrhiza plants are generally considered to be resistant to diseases due to their small size and floating nature. However, there are still some diseases that may affect the plant, including fungal leaf spots, root rot, and bacterial wilt. To manage fungal leaf spots, infected plants should be removed immediately to prevent the spread of the disease. Keeping the water in which the plants are growing clean and well-oxygenated can also help prevent the development of leaf spots. Root rot can be prevented by avoiding overwatering and ensuring that the plant is not submerged for too long in standing water. The use of a well-draining substrate can also help prevent root rot. Bacterial wilt is a more severe disease compared to fungal leaf spots and root rot. Unfortunately, there is no known treatment for this disease. The best approach is to prevent its occurrence by maintaining a clean growing environment, avoiding overwatering, and frequently changing the water.
Pest Management
Common pests that may affect Wolffia arrhiza include mosquito larvae, snails, and aphids. Mosquito larvae can be controlled by adding mosquito fish to the water or using biological mosquito control agents such as Bacillus thuringiensis israelensis (Bti). Snails, on the other hand, can be removed by hand or by using traps. Aphids can be treated with insecticidal soap or neem oil. However, it is important to be careful when using pesticides as they may harm other aquatic organisms in the ecosystem. Prevention is always better than cure when it comes to pest management. Keeping the growing environment clean, reducing overcrowding, and regularly inspecting the plant for signs of pests can help prevent infestations from occurring.
