Glossary Plant Breeding

Mechanical Errors. Errors occurring in the execution of an experiment. These can occur
during layout, management and care of the experiment and data keeping and
recording. These are primarily human errors, and thus cannot be effectively controlled
by statistical techniques. These can make a substantial difference in the experimental
results. Their prevention depends largely on the awareness and the skill of the
researcher in relation to the various operations of the experiment.
Medium. Any material on which experimental cultures are grown. Although composition
of a medium varies according to the objectives of a programme, it usually consists of
sugar (as a source of energy), certain inorganic salts, one or a few phytohormones and
vitamins, and agar (as a solidifying agent if a solid medium is to be prepared).
Median. The middle value of a series of observations arranged in ascending or
descending order of their magnitudes. It divides the series into two equal halves, half
the number of the observations lying above it and half below. If the number of
observations in a series is odd, then (N+1)/2 is the middle item of the series (where N
is the total number of observations). However, in case of an even series data, two
middle items [(N/2) and (N/2+1)] will represent the median.
Mega Base Pairs. One million nucleotide pairs.
Megaenvironment. Broad (not necessarily continuous often transcontinental) area with
similar biotic and abiotic stresses, cropping systems and consumer preferences.
Analysis of megaenvironment is performed by AMMI model.
Megasporangium. A sporangium producing megaspores.
Megaspore. One of the four haploid spores originating from the meiotic division of the
diploid megaspore mother cell in the ovary, and which gives rise to the mega
gametophyte.
Megaspore Mother Cell. The diploid (2n) cell in the ovary that gives rise to four haploid
megaspores through meiosis.
Meiocyte. A cell embarking upon meiosis (or a cell in which meiosis takes place).
Meiosis. A kind of nuclear division occurring in reproductive cells, which results in
production of gametes (animals) or sexual spores (in plants) with haploid (n)
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