Experiment Station Record, Volume 92, January-June, 1945 Page: 31
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19453 AGRICULTURAL BOTANY 31
the roots of sand dropseed showed them to respond to the various experimental
solutions' in the same manner as timothy roots. The origin and subsequent growth
of root hairs in the dropseed roots are described, and an explanation to account
for the variable position of the mature hair is discussed.
The effect of lack of oxygen on meiosis in Tradescantia, L. M. STEINITZ.,
(Univ. Calif.). (Amer. Jour. Bot., 31 (1944), No. 7, pp. 428-443, ills. 17).Study
of mitosis in barley seedlings (E, S. R., 90, p. 463) had indicated that
absence of 02 for nonlethal periods may produce cytological aberrations. It remained
to determine whether any phase of the chromosome cycle is more sensitive
than another and to obtain a quantitative measure of the effects of anaerobic treatment;
this phase of the study,was made with Tradescantia. During meiosis in the
microsporocyte, 48 hr. under anaerobiosis resulted in severe injury; 12 hr. of nitrogen
treatment induced abnormalities measurable at the end of the treatment and
during recovery in air. These abnormalities included lengthening of the prophase
and interphase of meiosis; decrease of terminalization of.chiasmata at metaphase;
formation of chromosome fragments, bridges, lagging chromosomes, and restitution
nuclei; induction of irregularities in chromosome distribution; and formation of
giant microspores, as a result of failure of cytokinesis of the sporocyte. These giant
cells degenerated before pollen grain division. The reaction of dividing cells to
lack of 02 indicates that cells undergoing meiosis are much more sensitive than
cells in mitosis as determined in the barley experiments. The most sensitive stage
of meiosis is prophase, and probably late zygotene and early pachytene. Secondary
sensitive stages were found to be metaphase I and interphase.
Veratrine, a new polyploidy-inducing agent, E. R. WITKUS and C. A. BERGER
(Jour. Hered., 35 (1944), No. 5, pp. 130-133, illus. 2).-The cytological effects
of this substance were found similar to those of colchicine but.with a few interesting
differences in the mechanism by which polyploidy is induced. Being effective within
a much narrower range of treatment than colchicine, it will probably prove less
useful as a tool to the plant breeder.
Cell polarity and the development of form in cucurbit fruits, E. W. SINNOTT
(Amer. Jour. Bot., 31 (1944), No. 7, pp. 388-391, illus. 10).--In ovaries of various
lines where the relative rates of growth in length and width had been determined,
a close relation was found between the orientation of the mitotic axes and the
direction of growth of the organ. Where these axes were preponderantly (or
nearly so) parallel to the organ axis, growth in length was the more rapid; where
mitotic figures were oriented equally in all directions, length and width were equal
in growth rates. The orientation of the telophase axis closely approached that of
the actual division, but the anaphase and metaphase did so with progressively less
exactness, suggesting that the figure at first rotates somewhat but later settles down
to its final position. This position seems to be determined by the polarity of the
cytoplasmic body of the cell. The establishment of this cytoplasmic body is the first
visible expression of the morphogenic control of dimensional growth rates and
thus of organic form.
The development of vessels in angiosperms and its significance in morphological
research, I. W. BAILEY (Amler. Jour. Bot., 31 (1944), No. 7, pp. 421-428,
illus. 9).--The irreversible phylogenetic trends in the' origins and specializations of
vessels are so comprehensive and reliable that they are believed ~to deserve serious
consideration in various lines of botanical research. Their significance in the fields
of comparative and developmental morphology are here discussed in some detail.
There are 32 references.
The strophiole and other seed structures associated with hardness in Melilotus
alba L. and M. officinalis Willd., J. N. MARTIN and J. R. WATT (Iowa State Col.
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U.S. Department of Agriculture. Agricultural Research Administration. Office of Experiment Stations. Experiment Station Record, Volume 92, January-June, 1945, book, 1947; Washington. (digital.library.unt.edu/ark:/67531/metadc5064/m1/44/: accessed February 25, 2017), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.