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ELONGATION OF THE COTTON FIBER
by
Joseph Charles O’Kelley
A Dissertation Submitted to the
Graduate Faculty in Partial Fulfillment of
The Requirements for the Degree of
DOCTOR OF PHILOSOPHY
Major Subjeoti Plant Physiology
Approved!
£x £tCL
,.,
Dean of Graduate College
Iowa State College
1950
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UMI Number: DP12887
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TABLE OF CONTESTS
Pag©
introduction....................................... 1
REVIEW OF LITERATURE................................. 3
MATERIAIS AND METHODS................................. 19
Materials . . . . . . . . ............... . . . . . 19
Tissue Cultures . . . . * ............ . ......... . 19
Growth Measurements of Bolls and Fibers.............. 20
Cell Wall Structure ........... 21
Carbohydrate Determinations . . . . . . . . . . . . . . 24
Nitrogen Determinations ................. 26
EXPERBENTAL RESULTS .....................* ........ 29
Growth Measurements and Rates of Fiber Growth . . . . . 29
Structure of the Fiber Wall . . . . . . . . . . . . . . 49
Chemical Changes in Developing Fibers.......... ♦ . 60
Carbohydrate Change© . . . . . . . . . . . . . . . 60
Changes in Nitrogen Content of Cotton Fibers ... 74
DISCUSSION............................ SI
s m w m .......................... 89
LITERATURE CITED................. . 91.
AC«5KIUSG®NTS .................................. 97
T97<? V
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IOTHODTJCTXOH
Cotton fiber growth deserves study not only because of its
economic importance, but also became it is in many ways better
suited than any other plant material for use in investigating the
processes of ceil elongation. Cotton fibers occur within the boll
as an essentially homogeneous tissue and can be easily separated
from the other tissue of the seed and boll. Since the fiber origi-*
nates and ends as a single cell, elongation can be studied free of
the complications that arise in the study of most plant tissues, in
which cell division occurs along with elongation. Primary and
secondary wall formation are distinctly separate processes in the
cotton fiber. Both continue for a relatively long period, making
possible studies that are not easily carried out with more rapidly
growing and maturing tissues, Finally, the great elongation of the
fiber makes it an excellent subject for study.
Previous studies of cotton fiber development have dealt mainly
with secondary wall formation, the differentiation phase of growth*
The elongation phase lias received much less attention. For this reason
this investigation deals primarily with fiber elongation. In certain
cases, however, the study was extended to include differentiating fibers
when such action appeared desirable. The present study proceeded along
three related lines of investigationi
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1* Bates of fiber elongation and factors affecting elongation
rates*
2* the structure of the cell wall during cell elongation*
3* Changes in the carbohydrates and in the nitrogen compounds
of developing fibers*
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REVIEW CF LITERATDRE
The use of cotton for the wearing of cloth appears to hare
originated in India at such an ancient time that it preceded written
records of human life* Although cotton has been cultivated for many
centuries, almost all of what is known concerning the growth of cotton
fibers has been discovered in the last fifty years. In the latter part
of the nineteenth century attention was directed toward chemical and
physical studies of nature cotton fibers and agronomic problems involved
in the cultivation of cotton. Intensive programs of cotton breeding and
studies of cotton diseases were carried out, while the physiology of the
plant and particularly the development of the fiber were largely ignored.
The elongation phase of cotton fiber growth was imperfectly known
at the turn of the century. What was known of it was reviewed by Evans
(1896), At this time it was recognized that the fiber appears a con
siderable time before the seed is full grown, and that it commences as
the development of a cell on the surface of the ovule, Ivans reported
the method of growth, as described by Bowman (1882), to be by the
successive linear development of cells, the and walls of which were
believed to be absorbed until an elongated single cell was produced.
This concept of the growth of the fiber was corrected by Bowman (1998),
who determined that the fiber consists of a single elongated cell,
continuous throughout its own length, and that it originates as a
single call.
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Kbowledge of the origin and early growth of the cotton fiber
remained in tide incomplete state until the intensive studies of
Balls in Egypt. Balls (1912) described the development of the fiber
in considerable detail. Be discovered that the fibers begin develop
ment before fertilization is completed, by radial growth of the epi
dermal cells of the seed coat, that the young fibers at once assume
their mature diameter, about twice that of the unaltered epidermal
cells, that the nucleus lies at the tip of the swelling at first and
after the third day of growth moves to the middle of the cell, whore
it remains alive until the bell opens. He reported that the growth
of the fiber is at first confined to elongation, and that the boll
attains almost full size before any secondary thickening of the fiber
wall occurs. He also believed that the fiber attains its final length
before secondary thickening begins, but did not establish this point
at this time. Balls found the elongation period of the cotton he
studied to be about twenty-five days, approximately half of the total
maturation period*
The time of origin of the lint hairs was a subject of controversy
for several years, beginning with the observation of Balls (1915) that
the density of lint cm the seed is determined the first day after ferti-
/
lization, that lint hairs do net originate after this time. Singh (1931),
studying the early stages of fiber development, found that on the day the
flowers open, epidermal cells of the ovule bulge out in the form of tiny
balloons, and that these are sparsely distributed on the epidermis of the
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©role* He observed that as the fertilized ovule grew the epidermal
cell number increased} that thirty-six hours after fertilization fibers
occurred in different stages of development, and that forty-eight hours
after fertilization almost all epidermal cells were involved in the
formation of fibers. Gulatl (1930), making calculations of the number
of hairs on one-day-old ovules and mature seeds, found a mean value for
the number of hairs on one-day-old ovules of 2,208, and a mean value
for the number of hairs on mature seeds of 14,809, He also observed
epidermal cells in the process of division in ten-day-old ovul.es, and
observed growing fibers of greatly different lengths in close prcxdmity
to one another. He concluded, as did Singh, that fibers continued to
originate after the day of flowering, Parr (1931), on the basis of
observations similar to those of Singh and Gulati, concluded that some
fibers were formed from cells arising as the result of cell divisions
in the ovule epidermis subsequent to fertilization of the ovule, Darrltt
(1932), in a criticism of the findings of Gulatl and Parr, did not confirm
the occurrence of mitotic division of epidermal cells in ovules seven days
after flowering. Additional studies by Parr (1933) on young ovules sup
ported her original conclusion, Ayyar and Ayyangar (1933), Gulati (1934),
and Sheffield (3-936) gave further evidence to support the conclusion that
fibers may be formed after the day of fertilization, Anderson and Kerr
(1938), after studying early growth of the fiber, expressed the opinion
that the fibere originating within two or three days after the date of
flowering become the commercial fibers and that others, which may originate
as late as ten days after flowering, are the linters of the seed, Barritt
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