7/28/2019 bgfhf

1/4

Saprophytes are those plants which grow and live on dead and decaying

organic matter of animals and plants. Many bacteria and fungi have this

mode of nutrition. Saprophytes are of great economic importance because

the convert complex organic substance of dead organisms into minerals.

Souring of milk, formation of curd and vinegar are examples of the activity

of saprophytic bacteria. Many fungi are saprophytic e.g., Yeast, Mucor,

Penicillium,Agaricus. Fungi growing on wet bread, leather goods and wood

are example of saprophytes. Splanchnwn and Hipnum mosses are examples

of saprophytes. In Pteridophytes Botrychium and some species of

Lycopodium are partial or complete saprophytes. Some Angiosperms are

also saprophytes.

E.g., Neottia, and Monotropa. Neottia is known as Bird's nest orchid. It

grows on humus rich soil. The plant has underground rhizome which form

a cluster of roots. The root hairs are absent. The roots of Neottia are

associated with endotrophic mycorrhiza. The fungus absorbs from humus

its food and the cortex cells of the root digest even the cell walls of fungus.

Thus they absorb their food from fungus. Actually Neottia is a parasite on

fungus. The plant produces aerial shoots which is fleshly and light brown.

This stem bears a few brown scale leaves and a spike of orange coloured

flowers.

Insectivorous plant

Plant that can capture and digest live prey (normally insects), to obtainnitrogen compounds that are lacking in its usual marshy habitat. Some are

passive traps, for example, the pitcher plants Nepenthes and Sarracenia.

One pitcher-plant species has container-traps holding 1.6 l/3.5 pt of the

liquid that digests its food, mostly insects but occasionally even rodents.

7/28/2019 bgfhf

2/4

Others, for example, sundews Drosera, butterworts Pinguicula, and Venus

flytraps Dionaea muscipula, have an active trapping mechanism.

Insectivorous plants have adapted to grow in poor soil conditions where the

number of micro-organisms recycling nitrogen compounds is very much

reduced. In these circumstances other plants cannot gain enough nitratesto grow. See alsoleaf.

Near-carnivorous plants are unable to digest insects, but still trap them on

their sticky coated leaves. The insects die and decay naturally, with the

nutrients eventually becoming washed into the soil where they finally

benefit the plant.

Symbiotic Relationships

Two important symbioses involve fungi: the mycorrhizae that

occur on the roots of almost all vascular plants and the lichens

that have evolved entirely different body forms from those of

their symbionts.

Mycorrhizae

Fungi and the roots of almost all vascular plants form mutualistic

associations calledmycorrhizae (singular, mycorrhiza). The

fungus gets its energy from the plant, and the plant acquires an

efficient nutrient absorbing mechanismthe actively growing

hyphae that penetrate regions of the soil untapped by root hairs.

Phosphate uptake especially is increased when mycorrhizae are

present.

Two general types of mycorrhizae occur, differentiated by

whether the hyphae livewithin the cortical cells of the roots or

http://www.talktalk.co.uk/reference/encyclopaedia/hutchinson/m0007919.htmlhttp://www.talktalk.co.uk/reference/encyclopaedia/hutchinson/m0007919.htmlhttp://www.talktalk.co.uk/reference/encyclopaedia/hutchinson/m0007919.htmlhttp://www.talktalk.co.uk/reference/encyclopaedia/hutchinson/m0007919.html

7/28/2019 bgfhf

3/4

remain outside the cells: endomycorrhizae(endo = within;

myco = fungus; rhizae = roots) and ectomycorrhizae (ecto =

outside). Zygomycete taxa are components of most

endomycorrhizae while basidiomycetes and a few ascomycetes

form ectomycorrhizae.

Lichens

The symbiotic relationship of fungi with either algae or

cyanobacteria produces a bodya lichenso distinctly different

from either of its symbionts that it is treated as a separate

organism. The fungal hyphae give the lichenthallus

itscharacteristic shape, and the cells of its photosynthetic partner

are dispersed among them. While the algal or cyanobacterial

member can live independently, the fungus cannot, so the fungus

in essence is a parasite on the photosynthesizer in the lichen

thallus. The fungus, however, provides a home for the

photosynthetic cells as well as absorbing water and nutrients thatthe photobiont uses. This makes the symbiosis mutualistic as

much as parasitic in the view of some biologists.

Life is becoming precarious for lichens in many urban

environments today. Many lichens are intolerant of air pollutants.

They have no means of getting rid of the elements, toxic or

useful, which they absorb. Sulfur is particularly toxic to many,

and sulfur dioxide released from burning coal has eliminated

many susceptible species from cities. Lichens can be used as

biomonitorsand warningsof the quality of the air we breathe.

7/28/2019 bgfhf

4/4