Tag: botany

Like all green plants, algae produce oxygen during the daylight hours as a by-product of photosynthesis. This is usually a major source of oxygen in fish ponds. In darkness, however, all plants consume oxygen, including algae. Algae blooms in natural water bodies or fish ponds normally produce much more oxygen in the daylight than they consume during the night, but some situations reduce the amount of oxygen a bloom produces without reducing its nighttime oxygen consumption. Trace minerals or nutrients needed by the algae are occasionally used up, causing some or even all, of the bloom to die back temporarily. The resulting bacterial decomposition and loss of normal oxygen production can lead to oxygen depletions and fish kills. Pond water generally changes from a deep green to black, gray, brown or clear after a phytoplankton die-off. 

Facultative parasites are organisms which do not completely depend on a host for completing its life cycle, but may become parasitic in absence of food or other favorable conditions

Cuscuta (Doddar) plant is obligate or total stem parasite. It completely lacks chlorophyll and has no connection with the soil after the seeding stage. Therefore it is totally dependent on the host for organic food materials and supply of water and minerals salts.

a) Pathology deals with the study of the nature and causes of diseases. 

Viscum is a partial stem parasite among the following because it depends on its host for only water and minerals. It can prepare its own food through photosynthesis as it is chlorophyllous.