Cotton (source code)
= Cotton
<Cotton> denotes <plants> of the <taxonomic genus> <Gossypium>, grown especially for the long fibres associated with their <seeds>. The <plant>, an individual fibre and a textile made from many fibres are different levels of organization.<Gossypium in Plants of the World Online>[Accepted Gossypium genus record and classification]{ref}
A <cotton> fibre is a striking <cell elongation> example: one <cell> grows outward from the <seed coat> <plant epidermis>. A 2001 study described fibres reaching about $2.5$–$3.0\,\mathrm{cm}$ in approximately 16 days after flowering. These long <cells> provide a way to study growth without mistaking an increase in cell number for elongation of one <cell>.<The control of single-celled cotton fiber elongation by developmentally reversible gating of plasmodesmata and coordinated expression of sucrose and K+ transporters and expansin by Y. L. Ruan and others>[Abstract: single-cell origin, length and developmental interval]{ref}
The experiment followed a <fluorescent tracer> from the <seed coat> into growing fibres with <confocal microscopy>. Access through intercellular connections involving a <plasmodesma> changed during development: tracer entry was seen early, blocked around day 10 and seen again around day 16. Transporter expression and <turgor pressure> measurements supplied complementary information about solute entry and growth.<The control of single-celled cotton fiber elongation by developmentally reversible gating of plasmodesmata and coordinated expression of sucrose and K+ transporters and expansin by Y. L. Ruan and others>[Abstract and Figure1: reversible tracer access and coordinated physiological changes]{ref}
For an original calculation, a fibre that adds $30\,\mathrm{mm}$ over 16 days has an average extension rate of $1.875\,\mathrm{mm}$ per day. That quotient is not an instantaneous rate and does not imply uniform growth throughout development. Measuring fibre length at several ages distinguishes a mean rate from a changing growth trajectory.
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