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71.
Measurements of net CO2 exchange, malate accumulation, properties and capacity of phosphoenolpyruvate carboxylase (PEPC, EC 4.1.1.31) in leaves of different ages of two short-day dependent Crassulacean acid metabolism (CAM) plants (Kalanchoe blossfeldiana v. Poelln. Tom thumb and K. velutina Welw.) show that, in both species: a) young leaves from plants grown under long days display a CO2 exchange pattern typical of C3 plants; b) leaf aging promotes CAM under long-day conditions; c) short-day treatment induces CAM in young leaves to a higher degree than aging under long days; d) at least in K. blossfeldiana, the PEPC form developed with leaf aging under long days and the enzyme form synthetized de novo in young leaves grown under short days were shown to have similar properties. Short days also promote CAM in older leaves though at a lesser extent than in young leaves: The result is that this photoperiodic treatment increases the general level of CAM performance by the whole plant. The physiological meaning of the control of PEPC capacity by photoperiodism could be to afford a precisely timed seasonal increase in CAM potentiality, enabling the plant to immediately optimize its response to the onset of drought periods.Abbreviations CAM
Crassulacean acid metabolism
- PEP
phosphoenolpyruvate
- PEPC
phosphoenolpyruvate carboxylase (EC 4.1.1.31)
- LD
long day
- SD
short day 相似文献
72.
Summary Pectic strands are shown to connect the lower stomatal ledges and to develop across the posterior chamber of a number of plant species. Similar strands are formed between guard cells and subsidiary cells, and between epidermal cells. 相似文献
73.
Previous work in our laboratory led to the isolation of a cadmium (Cd)-resistant variant (Cdr2C10) of the line CHO Chinese Hamster cell having a 10-fold greater resistance to the cytotoxic action of Cd2+ compared with the CHO cell. This resistance was attributed to an increased capacity of the Cd2+-resistant Cdr2C10 subline to induce synthesis of the Cd2+- and Zn2+-binding protein(s), metallothionein(s) (MT). Evidence that Cd2+ behaves as an analog of the essential trace metal, Zn2+, especially as an inducer of MT synthesis, suggested that the Cdr and CHO cell types could be employed to investigate cellular Zn2+ metabolism. In the present study, measurements were made to compare CHO and Cdr cell types for (a) growth as a function of the level of ZnCl2 added to the culture medium, (b) uptake and subcellular distribution of Zn2+, and (c) capacity to induce MT synthesis. The results of these measurements indicated that (a) both CHO and Cdr cell types grew normally (T
d≊16–18 h) during exposures to Zn2+ at levels up to 100 μM added to the growth medium, but displayed abrupt growth inhibition at higher Zn2+ levels, (b) Cdr cells incorporate fourfold more Zn2+ during a 24-h exposure to the maximal subtoxic level of Zn2+ and (c) the CHO cell lacks the capacity to induce MT synethesis while the Cdr cell is proficient in this response during exposure to the maximal subtoxic Zn2+ level. These findings suggest that (a) the CHO and Cdr cell systems will be useful in further studies of cellular Zn2+ metabolism, especially in comparisons of Zn2+ metabolism in the presence and absence of induction of the Zn2+-sequestering MT and (b) a relationship exists between cellular capacity to induce MT synthesis and capacity for cellular
Zn2+ uptake. 相似文献
74.
Modification of oligosaccharide-lipid synthesis and protein glycosylation in glucose-deprived cells 总被引:9,自引:0,他引:9
S J Turco 《Archives of biochemistry and biophysics》1980,205(2):330-339
Incubation of vesicular stomatitis virus-infected glucose-starved baby hamster kidney cells with [35S]methionine results in the synthesis of all viral proteins. However, as judged by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and tryptic peptide mapping, the G protein is abnormally glycosylated. Metabolic labeling of the oligosaccharide-lipid precursors with [3H]mannose for 15 min, followed by Chromatographic and enzymatic analysis, indicates that the radiolabeled lipid-linked oligosaccharides are devoid of glucose in contrast to the glucosylated oligosaccharide-lipids synthesized by cells grown in the presence of glucose. Also, in contrast to control cells, examination of the glycopeptide fraction reveals the presence of [3H]mannose-labeled glycopeptides which are resistant to erado-β-N-acetylglucos-aminidase H and are smaller in size than glycopeptides from mature vesicular stomatitis virus. In order to observe these effects, a minimum time of 5 h of glucose deprivation is necessary and the addition of 55 μm glucose or mannose to the medium reverses these effects. These results indicate that vesicular stomatitis virus-infected BHK cells deprived of glucose are unable to glucosylate the oligosaccharide-lipid intermediates and, consequently, are unable to glycosylate the G protein normally. 相似文献
75.
Summary In order to explore interrelations between S nutrition, soluble sugars, leaf area, nodulation and N2 fixation, greenhouse experiments were done with several levels of S added to perlite-sand cultures or to a moderately S-deficient soil. Sulfur had indirect effects on nodulation and N2 fixation, possibly by improving sugars supply and N metabolism.In perlite-sand culture, leaf area increased with concentrations of supplied S up to 50 and 200 M for symbiotic and N-treated plants respectively, then decreased at higher concentrations. Plant yield and total sugars content (mg per plant) for the N-treated plants behaved similar to leaf area in response to added S but in the symbiotic plants maximum values were obtained at 100 M S. In soil, Mo had no effect on growth but interacted significantly with S in affecting total sugars content. High levels of S depressed sugars content at low Mo but raised it at high Mo.Sulfur increased the N content of soil-grown plants. It increased the N content of plants grown in perlite-sand culture except at very high levels of S. There was little effect on concentration of N in the shoots. Nitrogen content correlated significantly with leaf area and sugar content, and highly significantly with S concentration in the shoots. 相似文献
76.
Summary Inclusion of sucrose in the solution applied to soybean (Glycine max L. merr.) leaves much reduced the severity of the damage to the leaves from application of urea and, to a lesser extent, from application of phosphorus (P) as orthophosphoric acid. Sucrose had no evident effect on P absorption. Damage to the leaves from joint application of orthophosphoric acid and urea exceeded the sum of the damage caused by the substances individually. Urea did not seem to influence P absorption, but the effect, if any, was not readily determined because nearly all values for P absorption exceeded 90%.Neutralization of orthophosphoric acid with nitrogen-containing organic bases, including choline, guanidine, and guanyl urea, did not prove useful as a technique for increasing the quantity of orthophosphate that could be applied without damage to the leaves.Absorption and translocation of orthophosphate by corn (Zea mays L.) and soybean leaves were not influenced by the pH of the solution within the range from 2 to 10. Absorption of tripolyphosphate by corn leaves decreased with an increase in pH of the solution applied, but translocation of the absorbed P was not influenced by pH. With soybeans, absorption of tripolyphosphate decreased with an increase in pH of the solution. Translocation of P applied to soybean leaves as tripolyphosphate was less than 5% of the amount absorbed within the first 24 hr and decreased with an increase in pH after 10 days. 相似文献
77.
Leaf tissues of Zea mays were examined with a transmission electron microscope and a high-voltage electron microscope. Tubular extensions (invaginations) of the plasmalemma were found in vascular parenchyma cells and thick-walled, lateformed sieve elements of intermediate and small veins, and in epidermal, mesophyll, and sheath cells of all leaves examined. No continuity seems to exist between the tubules and other cellular membranes. 相似文献
78.
The period length of the leaf movement rhythm of Trifolium repens L. is lengthened by continuously offered cAMP (0.5–1.0 mol m-3) and theophylline (0.5–4 mol m-3). At the higher concentrations this effect is more pronounced and the rhythm damps out faster. Imidazole (0.5 and 1 mol m-3) has no effect on the period length; however, after 5 mol m-3 the rhythm is abolished. Offered as 4 h pulses the resulting phase response curves for cAMP and imidazole are similar and show delays of up to 4 h during the day position of the leaves. Theophylline pulses lead to delays of up to 5 h during closure and advances of up to 3 h during opening. No phase shift is brought about by 4-(3,4-dimethoxybenzyl)-2-imidazolidone. The results do not support the cAMP-model of the circadian clock which has been proposed by Cummings (J. theor. Biol. 55, 455–470; 1975). The effect of the substances tested could, however, be based upon influences on the transport of Ca2+.Abbreviations ATP
adenosine triphosphate
- cAMP
cyclic adenosine 35 monophosphate
- AMP
adenosine 5 monophosphate
- AC
adenyl cyclase
- PDE
phosphodiesterase
- LL
continuous light 相似文献
79.
Ryoko Imaichi 《Journal of plant research》1983,96(3):159-170
The third petiolar bud ofHypolepis punctata appears on the basiscopic lateral side of the petiole above the fairly developed first petiolar bud. This investigation clarified
the fact that the third bud is formed neither by the activity of the meristem of the first bud nor by the meristem directly
detached from the shoot apical meristem, but is initiated in the cells involved in the abaxial basal part of the elevated
portion of the leaf primordium. Thus the third bud is of phyllogenous origin. This investigation further revealed that the
cells to initiate the third bud are originally located in the abaxial side of the leaf apical cell complex like the cells
to initiate the first bud, but are not incorporated into the meristem of the first.
After the first, second and third petiolar buds have been initiated, they are carried up into fairly high regions on the petiolar
base by the intercalary growth which occurs in the leaf base below the insertion level of the first and the second buds. 相似文献
80.
Margit M.K. Nass 《Gene》1983,21(3):249-255
A precise physical map, containing the structurally and operationally defined D-loop origin, terminal region, and direction of heavy-strand replication, has been constructed for mitochondrial DNA (mtDNA) from ovary (CHO-KI) and lung cells of Chinese hamster (Cricetulus griseus 2 N = 22), and compared with our previously established genome coordinates for mtDNA from Syrian hamster ( Mesocricetus auratus 2 N = 44). All four HpaI sites in Cricetulus are conserved in Mesocricetus (8 sites). Extensive variation exists for hexanucleotides cleaved by EcoRI HindIII PstI. KpnI and BamHI. Sequence divergence between Chinese and Syrian hamster mtDNAs, as reflected from analysis of the mapped recognition sites for these six endonucleases, is estimated as 5–9% base substitutions. mtDNAs from both hamster and several other mammalian species contain a commonly conserved HpaI site in the region of light strand initiation. 相似文献