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61.
—The period during which trans-synaptic stimulation is required by the rat superior cervical ganglion for induction of tyrosine hydroxylase by reserpine has been studied. Ganglia were decentralized on one side at various times before or after an injection of reserpine. The tyrosine hydroxylase activity of the denervated and control ganglia was assayed 72 h after drug treatment. When decentralization was performed 8 h after an injection of reserpine the increase in tyrosine hydroxylase activity was blocked in the denervated ganglia. Decentralization 12 h after reserpine treatment or later had no effect on the enzyme induction. The actual increase in tyrosine hydroxylase activity occurred between 24 and 48 h after injection of reserpine. 相似文献
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The genetics of selfing with concurrent backcrossing in breeding hybrid sugar beet (Beta vulgaris altissima L.) 总被引:1,自引:0,他引:1
I. J. Mackay J. P. Gibson P. D. S. Caligari 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1999,98(6-7):1156-1162
Sugar beet hybrids are produced by crossing a cytoplasmic male-sterile (CMS) line with a pollinator. New CMS lines are produced
by crossing a fertile plant to an existing CMS line. The fertile plant is also selfed. In the following generation, one of
the selfed, fertile progeny is paired and isolated with one of the crossed, CMS progeny, to give a second generation of selfing
and crossing. Over a series of such crosses and selfs, a new fertile inbred line and its corresponding, near-isogenic CMS
partner are produced. Selection among lines takes place at one or more stages of the backcrossing programme. A method is presented
here for calculating the genetic variances and covariances within and between lines and generations based on a derivation
of additive genetic relationships modified from an approach widely employed in animal breeding. The genetic variances and
covariances are used to predict response to selection from varying strategies, from which optimum schemes can be determined.
Results suggest that selection should generally take place after three generations of backcrossing when the fertile plant
used to initiate the backcrossing process is not inbred, but can take place after generation two when the fertile plant is
inbred. Doubled haploid production is unlikely to provide an extra advantage that would be worthwhile in such a system. The
method developed here can be used to explore a wide range of more complex breeding systems.
Received: 27 July 1998 / Accepted: 19 October 1998 相似文献
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Wayne A. Mackay 《In vitro cellular & developmental biology. Plant》1999,35(4):283-284
Summary There are many Chihuahuan desert species that have potential as landscape plants for the arid communities of the southwestern
United States [agarita, Berberis trifoliata Moric.; Mexican buckeye, Ungnadia speciosa Endl.; Texas madrone, Arbutus xalapensis var. texana (Buckl.). A. Gray]. Within these plant populations, there are superior genotypes that offer even greater interest for the
landscape. However, it is difficult to clonally propagate many of these species with conventional techniques, and the seed-derived
populations often do not breed true. Therefore, selection of superior genotypes in wild populations coupled with clonal propagation
through tissue culture may offer an attractive option. It is relatively easy to achieve disinfestation of explants from desert
plants due to a general lack of natural surface contamination by fungi and bacteria, even though interference from numerous
trichomes can impede good contact with disinfesting agents. However, there is only a narrow window of time that is ideal for
explant collection, because of the brief, periodic flushes of growth that characterize this unusual plant group. There may
be years when, due to the harsh environment, the amount of suitable explant material is severely limited. Phenolics and exudates
are also problematic in this group of plants, and acclimatization of ex vitro plantlets to the harsh desert environment is
a particular challenge. For these reasons, specific adaptations and modifications were necessary to achieve success with micropropagation
of desert plant species such as Mexican redbud (Cercis canadensis var. mexicana L.). 相似文献
70.
Summary Root hairs have been shown to enhance P uptake by plants growing in low P soil. Little is known of the factors controlling root hair growth. The objective of this study was to investigate the influence of soil moisture and P level on root hair growth of corn (Zea mays L.). The effect of volumetric soil moistures of 22% (M0), 27% (M1), and 32% (M2) and soil (Raub silt loam, Aquic Argiudoll) P levels of, 0.81 (P0), 12.1 (P1), 21.6 (P2), 48.7 (P3), and 203.3 (P4) mol P L–1 initially in the soil solution, on shoot and root growth, P uptake, and root hair growth of corn was studied in a series of pot experiments in a controlled climate chamber. Root hair growth was affected more by soil moisture than soil P. The percentage of total root length with root hairs and the density and length of root hairs on the root sections having root hairs all increased as soil moisture was reduced from M2 to M0. No relationship was found between root hair length and soil P. Density of root hairs, however, was found to decrease with an increase in soil P. No correlation was found between root hair growth parameters and plant P content, further suggesting P plays a secondary role to moisture in regulating root hair growth in soils. The increase in root hair growth appears to be a response by the plant to stress as yield and P uptake by corn grown at M0 were only 0.47 to 0.82, and 0.34 to 0.74, respectively, of that measured at M1 across the five soil P levels. The increase in root hair growth at M0, which represents an increase of 2.76 to 4.03 in root surface area, could offset, in part, the reduced rate of root growth, which was the primary reason for reduced P uptake under limited soil moisture conditions.Journal Paper No. 10,066 Purdue Univ. Agric. Exp. Stn., W. Lafayette, IN 47907. Contribution from the Dep. of Agron. This paper was supported in part by a grant from the Tennessee Valley Authority. 相似文献