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991.
992.
When an excised corn (Zea mays) root pretreated with chloride was exposed for 10 minutes to pulse labeling with 30Cl and then transferred to unlabeled chloride, the activity in the xylem exudate reached a maximum about 4 minutes after pulse labeling was discontinued and then declined sharply. The rate at which labeled chloride was transported across the root into the xylem and basipetally therein was on the order of 75 to 250 centimeters per hour. Consequently, symplasmic movement of chloride in corn roots is fast and may not be rate-limiting in transfer from the root surface to the xylem. Experiments on pulse labeling with 22Na gave similar results. A large fraction of the absorbed 22Na was not translocated into the exudate but was tightly sequestered in a cell compartment, probably the vacuole. 相似文献
993.
Summary
3H-serine+14C-indole were administered to tips of sterily-grown pea seedlings and of non-sterile oat coleoptiles. The Try and IAA produced were extracted and purified by paper chromatography, and their 3H/14C ratios were determined. The 3H/14C ratio of IAA was lower than the 3H/14C ratio of Try. However, the same decrease of the IAA 3H/14C ratio was found when 3H, 14C-Try was supplied instead of 3H-serine+14C-indole. This result supports the view that Try is the native IAA precursor and that no significant bypass from indole to IAA exists in the plant material used.Abbreviations IAA
indole-3-acetic acid
- IPyA
indole-3-pyruvic acid
- Try
tryptophan 相似文献
994.
NUCLEOLAR-DERIVED RIBONUCLEIC ACID IN CHROMOSOMES, NUCLEAR SAP, AND CYTOPLASM OF CHIRONOMUS TENTANS SALIVARY GLAND CELLS 总被引:3,自引:0,他引:3 下载免费PDF全文
The distribution of monodisperse high molecular weight RNA (38, 30, 28, 23, and 18S RNA) was studied in the salivary gland cells of Chironomus tentans. RNA labeled in vitro and in vivo with tritiated cytidine and uridine was isolated from microdissected nucleoli, chromosomes, nuclear sap, and cytoplasm and analyzed by electrophoresis on agarose-acrylamide composite gels. As shown earlier, the nucleoli contain labeled 38, 30, and 23S RNA. In the chromosomes, labeled 18S RNA was found in addition to the 30 and 23S RNA previously reported. The nuclear sap contains labeled 30 and 18S RNA, and the cytoplasm labeled 28 and 18S RNA. On the basis of the present and earlier analyses, it was concluded that the chromosomal monodisperse high molecular weight RNA fractions (a) show a genuine chromosomal localization and are not due to unspecific contamination, (b) are not artefacts caused by in vitro conditions, but are present also in vivo, and (c) are very likely related to nucleolar and cytoplasmic (pre)ribosomal RNA. The 30 and 23S RNA components are likely to be precursors to 28 and 18S ribosomal RNA. The order of appearance of the monodisperse high molecular weight RNA fractions in the nucleus is in turn and order: (a) nucleolus, (b) chromosomes, and (c) nuclear sap. Since both 23 and 18S RNA are present in the chromosomes, the conversion to 18S RNA may take place there. On the other hand, 30S RNA is only found in the nucleus while 28S RNA can only be detected in the cytoplasm, suggesting that this conversion takes place in connection with the exit of the molecule from the nucleus. 相似文献
995.
996.
Summary Experiments were conducted to determine the influence of N, P, and K and of the NP and NK interactions on root yields and
tissue concentrations of N, P, and K of rutabagas grown on a sandy loam soil under greenhouse conditions. Root yields were
increased by applications of N and K but not by added P. The yield response to N was dependent on K supply. The highest dry
matter content in roots was associated with the lowest rates of N and K and the lowest root yields.
The N content of tissue at the early vegetative stage increased with increasing rates of N and decreased with increasing rates
of P and K. The N content of root tissue at harvest increased at the highest rates of N but was unaffected by rates of P and
K. The P and K content of root tissue increased with increasing rates of P and K, respectively.
The levels of nutrients in early vegetative tissue associated with optimum yields were about 2.6, 0.24, and 2.0% for N, P,
and K, respectively. The corresponding values in the leaf tissue at harvest were about 1.2, 0.12, and 1.5% N, P, and K, respectively.
Contribution No.222. 相似文献
997.
Antti Huunan-Seppälä 《Journal of bioenergetics and biomembranes》1971,2(3-4):197-207
The effect of the polybasic substances Polybrene and spermine on the passive and active transport of monovalent cations in mitochondria was studied. These agents were found to stimulate the low amplitude swelling of mitochondria. Volume oscillations were induced by addition of substrate in the presence of spermine. In conditions where weak oscillations were obtained without these substances, oscillations were stimulated and their frequencies increased in the presence of Polybrene and spermine. Their effects were maximal with 100–300 moles spermine per litre and 3–5 mg Polybrene per litre. These results are discussed in relation to an interaction of the agents studied with membrane negative charges which may be important regulators of ion transport. 相似文献
998.
Brother and sister with trisomy 10p: a new syndrome 总被引:4,自引:0,他引:4
999.