Necrosis. Death of a cell or group of cells, while still part of the living plant.

Nectar - (1) A sugar fluid which is produced in the nectaries of some insect- pollinated flowers.
(2) A similar solution produced by fungi, to attract insects to disperse spores.

Nectary - A gland in some flowers, or other part of the plant, which is secreting nectar.

Neo-Darwinism - Used for describing the expanded and modified version of darwin's theory of evolution in terms of genetic and molecular biology. Collection of all such studies into a coherent evolutionary theory is known as modern synthesis.

Neoteny - Used for describing to phenomenon of arrested development of all cells in an organism except the cells in germ line. It results in an organism that is sexually mature but otherwise is having juvenile characteristic.

Neotype - Said of the plant specimen which is selected to act as standard taxonomic reference after irretrievable loss of all type material of the taxon.

Neritic - Living in the sea at a depth of less than 200 m.

Nerve - The midrib, or large vein in a leat.

Nervicolous - Said of a parasitic fungus which lives on the veins of leaves.

Net Assimilation Rate - The rate of increase in dry weight per unit of a leaf. This is approximately equivalent to the rate of photosynthesis.

Net Primary Production - Referring to the total amount of energy (in the form of bond energy of organic food material) which is made available in unit time by producers in an ecosystem to all the consumers of that ecosystem for their use.

Net Production - Referring to the total amount of energy made available in the form of food by a trophic level to its next higher trophic level (s) in unit time. This term is used for trophic levels except the producers.

Neutral Theory of Molecular Evolution - A theory postulating that there occurs random drift of selectively equivalent mutant genes as the cause of evolutionary change at the molecular level rather than the process of natural selection.

Neuromotor Apparatus - An organelle which is found in the motile cells. It is probably including gametes and zoospores, of the Chlorophyta. It is intimately associated with the nucleus, and is responsible for the production of flagella.

Neuter - (1) Aparently sexless, especially of strains of fungi which usually show sexuality.
(2) Of flowers in which the androecium and gynoecium are functionless or absent.

Neutral Spore - An asexual spore produced by some algae. The are produced in various ways, but are never in sporangia.

Niche - A term used for describing the status of a plant or animal in its community, i.e., its biotic and trophic relationship.

nif-Genes.Said of the genes governing fixation of atmospheric nitrogen in certain microorganisms particularly the bacteria.

Night Break Effecl - Used for the phenomenon of interference in normal flowering rhythm by permitting light artificially during night even for a very short duration or in low intensity. The effect is exhibited by many plants.

Night Temperature - Said of temperature which is prevailing around an organism during the period of darkness. In many plants, it greatly affects the growth. Low night temperatures are assumed to lower the respiration.

Nitrification - The oxicition of nitrogen-containing ions in the soil, by bacteria, e.g. Nitromonas oxidizes ammonium ions to nitrites and Nitrobacter oxidizes to nitrates.

Nitrogenase - Said of an enzyme system which is isolated from certain bacteria and is responsible for fixation of atmospheric nitrogen. In the presence of A TP and suitable electron donor, it reduces molecular nitrogen to ammonia.

Nitrogen Cycle - The circulation of nitrogen in Nature. Dead organic matter is converted to ammonium compounds during decay in the soil. These are converted to nitrates (see nitrification), which are utilized again by plants. Some of the nitrates are converted to gaseous nitrogen by the denitrifying bacteria, but this loss has been counterbalanced by the fixation of nitrogen by Bacillus radicicola and the tissue of legume root-nodules in which it grow.

Nitrogenfixation - The conversion of atmospheric nitrogen into organic nitrogen compounds. This is carried out by some soil bacteria, or by others living in the nodules on the roots of various plants, e.g., leguminous plants.

Nitrophilous - Said of plants characteristic of places having a high concentration of nitrogen compounds.

Node - (1) The part of stem where the leaf or leaves emerge.
(2) The zone on the thallus of the Charales, which gives rise to the lateral branches and the cortex.

Nomenclatural Type - Used for describing single element e.g., illustration, description, specimen etc., on which description associated with the original publication of a name was based. Type of a taxon may be a holotype, lectotype or neotype.

Non-Conjunction - The complete failure of synapsis.

Non-Disjunction Describing the pnenomenon of failure of paired homologues to separate during anaphase I of meiosis. This results in two gametes that are having both homologues and other two gametes that lack that chromosome. Such gametes are aneupoids.

Non-Persistenl - Used for describing the pesticides that break down and become inactive quite quickly e.g.,natural insecticides derris .and pyrethrum.

Nonsense Codon - Said of the name which was given originally to three triplet codons UAG, UCA and UGG which are not coding for any aminoacid but are acting as signals to stop transcription of mRNA. Two codons AUG and GUG that code for valine or methionine also act as signal to start transcription.

Northern Coniferous Forest. (boreal forest or taiga). Type of cold forest that is having relatively few types of trees, mainly fir, pine and spruce, with some deciduous trees like birches and larches. Conifers in these forests well adapt to long, cold winter sand retain leaves by taking advantage of short growing season. Boreal forests occur in North America and northern Eurasia.

Nucellus - The central tissue of the ovule having the embryo-sac and surrounded by the integuments(s).

Nuclear Budding - The production of. two daughter-nuclei of unequal size by constriction of the parent nuclous.

Nuclear Cap - Of the Blastocladiaceae, a body at one side of the nucleus of a zoospore or gamete.