- Plants grown as green manure
in India are sunn-hemp
- Farmyard manure consists of
a mixture of cattle dung and crop residue. FYM increases the aeration in
the soil, makes the soil loose and permits easy penetration of soil.
- Rhizobium is a Gram -ve bacterium. The protein lecithin present on the
root surfaces of a particular leguminous plant acts as a recognition
chemical between the plant and Rhizobium
to form nodules. Nitrogen fixation by Rhizobium
is better in the presence of phosphorus. Nitrogen fixation by Rhizobium takes place in the presence of leghaemoglobin, which is a pigment.
- Anabaena azollae is a cyanobacterium
present in the leaf cavities of Azolla.
An appreciable increase by 50% is observed in the yield of rice by the
use of Azolla.
- Azotobacter is a Gram -ve, aerobic, free living bacterium. Clostridium
and Chlorobium are anaerobic nitrogen
fixing bacteria. Rhodospirillum is an
example of photosynthetic and nitrogen fixing bacteria. The presence of Azospirillum lipoferum
was reported in Brazil. This nitrogen fixing
bacterium forms a loose association with the roots of maize, grass, etc.
- In the filamentous forms of cyanobacteria like Nostoc,
Anabaena, etc, there is a special, thick-walled cell called
heterocyst, which is a site of nitrogen fixation.
- The fungal hyphae in mycorrhiza
increase the absorption of water and some nutrients like nitrogen,
phosphorus, potassium and calcium.
- According to their chemical
composition, pesticides are classified into different groups such as organochlorines, organophosphates, carbamates, pyrethroids, triazines.
- DDT, BHC, aldrin are the examples of organochlorines.
These are chlorinated organic compounds, which get deposited in the
fatty tissues of animals and are called lipophilic.
These are contact poisons.
- Malathion, parathions, diazinon and fenitrothion
are organophosphates. Constituent of 'Flit' is malathion. They have a strong effect on the
nervous system, and thus, act as neurotoxins.
- Carbamates are the pesticides that
interfere with the nervous system functions. 'Baygon'
is chemically a carbamate called propoxur.
- Pyrethroids are the synthetic
derivatives of pyrethrin. They are obtained
from the inflorescence of Chrysanthemum cinerarifolium.
They act as insect repellents.
- Triazines are derived from urea. They
inhibit the Hill reaction of photosynthesis in weeds, and thus, control
- The growth of milk weed vine
in citrus plantation can be controlled by a mycoherbicide
developed from a fungus Phytophthora
- Lady bird beetles are used
to control a common pest called fluted scale insect on citrus trees.
- Gambusia fish feeds on the larvae of
mosquito, thus, controlling the mosquito population.
- Azadirachtin from neem
and nicotine from tobacco are effective insecticides.
- Protein toxins called thuriosides are produced by some bacteria like Bacillus
thuringinesis. These are highly toxic to
- Rotenone is a bioinsecticide extracted from the roots of Derris
- DDT is dichloro
It was discovered by Paul Muller.
- Bordeaux mixture consists of
lime (calcium hydroxide) and copper sulphate
dissolved in water.
- 'Devine' and 'Collego' are the fungal spore products recently
introduced to control weeds.