Plants need nutrients for the growth of their own body and in doing various functions. Nutrition is defined as the uptake and utilization of chemicals by a living organism for its normal growth and development. Plants show the following types of nutrition.
The plants which show this type of nutrition are known as autotrophs. They are green in colour and make their own food. They have chlorophyll and do photosynthesis in presence of carbon dioxide and water and light (sun rays). Therefore all plants are photoautotrophs. Some bacteria are chemoautotrophs.
The plants which show this type of nutrition are known as heterotrophs. They are normally not green and take their nutrition from some other sources. They are of the following types-
These are the non-green plants that live on some green autotrophic hosts. They take out ready-made food from the bodies of the host with the help of parasitic roots known as haustoria. These roots enter into the body tissues of host plants and absorb the food materials. Some parasites live on the stem of the host and are known as the total stem parasite. Example- Cuscuta (dodder plant or akashabela or amarbel).
Orobanche and rafflesia live on the roots of host plants and therefore, is known as total root parasite. Some plant grows as semiparasites or partial parasites on the hosts. They bear green leaves and can make their own food but depend upon the host plants for water and minerals. Example- Viscum is the partial stem parasite. Santalum is the partial root parasite.
These are the heterotrophic non-green plants that get their food from the dead organic matter. For example- fungi and some bacteria live as saprophytes.
Some plants show autotrophic nutrition but at the same time, they also show heterotrophic nutrition. They are known as mixotrophs. Such plants normally grow in soil that is poor in nitrogen. These plants get their nitrogen by trapping and killing insects. These plants are also known as insectivorous plants or carnivorous plants. Example- nepenthes, drosera, utricularia and dionaea are insectivorous plants.
Nepenthes or Pitcher Plant:
This plant grows in the north-eastern region of India and is an endangered plant. Its leaves are highly modified to trap insects. The basal part of the petiole is flat, broad and green and does photosynthesis. The rest of the petiole is very long and coiled. The lamina of the leaf is modified into a pitcher which has bright and attractive colours. The apex of the leaf is modified into an attractive lid. The pitcher has an opening known as the mouth or ostiole. The pitcher contains water and digestives enzymes. Insects get attracted to the pitcher because of its colours and nectar produced within it. Those insects which enter into the pitcher fall in the water and are not able to come out of the pitcher. The pitcher rim has got a large number of inwards directed hairs. These hairs don’t let the insect come out of the pitcher. Due to the irritation done to the hairs by the insect, the lid closes down. This way the trapped insects get killed inside the body of the pitcher and decomposed by the microorganisms and enzymes present in the pitcher water. The nutrients set free from the insect body are absorbed by the walls of the pitcher.
Droserra or Sundew Plant:
This plant also uses leaves in making food as well as trapping insects. The plants have rosette-like leaves with having a large number of hairs on their lamina. These hairs are glandular and secrete sticky droplets of fluid which even glitter (glinse) in presence of sunlight. This shine attracts the insects. The landing insects are trapped by these hairs and their sticky droplets. Then the hairs produce the enzymes which digest the body of the insects. The nutrient of a digested insect body is absorbed by the leaf lamina.
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