All living things are dependent either on other animals or plants for their food. Animals must constantly go in search of food. But plants remain fixed at one place. Some plants make their own food by using energy from sunlight to convert carbon dioxide from the air and water from the soil to make sugar.
Green leaves of the plants contain chlorophyll that carry out this process called photosynthesis. But a large number of plants are unable to produce their own food because of the absence of chlorophyll. These plants, therefore, feed on other plants or dead animals.
Plants that feed on other plants are called ‘parasites’. Those plants that feed on dead organic matter are called ‘saprophytes’. Saprophytes play an important role in the decay process by digesting and absorbing nutrients from dead material. All fungi and bacteria are saprophytes and they cannot produce food through photosynthesis. Some of the flowering plants are also saprophytes.
True fungi are mushrooms, toadstools, truffles, rusts, mildew and bread moulds. Mould is a collective name given to fungi that are not mushrooms. The fur moulds are sometimes seen on bread or vegetables. They grow on these food items and secrete an enzyme to break down the food into tiny parts that they can easily absorb.
Some plants are parasites. That is, they do not make food on their own but get water, minerals and food from other plants. Parasitic plants may or may not have chlorophyll. Plants like the mistletoe have green leaves and make some of their own food and take only water and minerals from the host plant through specially developed roots, which secure the parasite to the host and grow into the host’s stem.
True parasites such as dodders, which is a kind of morning glory, and cuscuta, are entirely devoid of chlorophyll and rely entirely on the host for food. Others like the mistletoe and rafflesia are partial parasites. Some are parasites of the stem and others attach themselves to the root.
The mistletoe can only grow if its seeds are left on branches or tree trunks. When the seeds sprout it sends a single root that ends up as a sucker (or sucking mechanism). It slowly enters the host tree and eventually may surround an entire branch.
When a dodder seed germinates, the young plant begins to grow in a circular fashion, searching for a mother plant. Once it gets a host, the thin stem of this plant twines around the host’s stem and starts taking food from the host. Broomrape and figwort are parasites of the root.
The most remarkable parasite plant is the rafflesia found in Southeast Asia. One species of this plant, the Rafflesia arnoldii found only in Sumatra, grows the largest flower which is over three feet across and weighs up to seven kg. Its flowers are purplish red and the entire flower can be smelt a mile away as it gives a distinct smell of rotting flesh! Though it grows large flowers, its roots and stems are small as it grows right on the forest floor attaching itself to roots of vines.