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n, 2n

The notations for the genetic and zygotic (diploid) or somatic chromosome number of a plant, e.g., 2n = 24 in rice.

Narrow brown leaf spot

A disease of rice caused by the fungus Cercospora janseana and Sphaerulina oryzina , which produces short, linear, brown lesions, most commonly on the leaves.

Narrow cross

A cross between parents that have many genes in common and only differ in a few.

Narrow leaved weeds

The monocot weeds are referred as narrow leaved weeds.

Narrow row planting

A method of planting in which the seed is planted in uncommonly narrow rows, closer than normal, for the given crop.   

Native crops

Crops which have been developed in a country, and not brought in from other Countries.

Natural cross pollination

Pollination of the plant by insects, wind, or floral parts without human intervention.

Natural insecticide

An insecticide produced from plant extracts.

Natural selection

The growing and survival of the best adapted plants in a given location, with selection occurring naturally without human intervention.

Neck blast

A form of blast disease where the rice panicle base becomes dark thereby called "rotten neck"; the panicles may fall over; the symptoms appear also on panicle branches.

Neck node

The nearly solid node between the uppermost internode of the culm and the panicle axis.


The panicle is enclosed by a spathe-like leaf or leaf sheath arising at the panicle base. Occasionally, additional bracts may arise at the base of the panicle branches.

Necrotic mosaic

A viral disease caused by the rice necrotic mosaic virus (rnmv). Polymyxa graminis is considered to be the vector of the rnmv. The disease occurs in Central and Southern Japan. Infected plants have elongate or spindle-shaped, yellow flecks and streaks on the basal portions of stems and sheaths. Plants may be moderately stunted with reduced tiller number and spreading growth habit. It can be transmitted by mechanical means and through the soil. There has been no evidence that insects or seeds transmit the disease.


Parasitic fungi that do not need a living host to be able to reproduce.


Swimming animals capable of navigation.


A chemical compound or physical agent that kills or inhibits nematodes.


Any of the class or phylum nematoda of elongated cylindrical worms parasitic in animals or plants free living in soil or water. Generally microscopic, worm like animals that live saprophytically in water or soil.

Net assimilation rate

The rate of plant weight increase per unit leaf area.

Net income

Gross farm income minus total farm costs.


A group of people or institutes located in different places but working together for a common goal.

Neutral soil

Specifically, a soil in which the surface layer, at least down to normal plough depth, is neither acid nor alkaline in reaction. Practically, a soil in which the pH of the surface soil ranges between 6.6 and 7.4.


Role and function of an organism specific in its habitat.


A chemical for the colorimetric determination of amino acids, which becomes violet to red when in contact with honeydew on filter paper. It is used to determine the feeding activity of the brown planthopper.

Nitrate assimilation

Uptake of nitrate by living organisms and conversion to cell substances.


The biochemical oxidation of Ammonium (NH4+) to Nitrate (NO3-).

Nitrification inhibitor

A chemical product used to slow down the release of Nitrate in organic manure.

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