摘要:

[8‐14C]Benzyladenine (BA) and [8‐14C]trans‐zeatin(tZ) were fed through the petiole to mature, detached green, yellow and variegated leaves ofSchefflera arboricola.Recovery of radioactivity from the plant material ranged between 4.2 and 22.1%. More radioactivity was recovered when tZ was applied compared to BA. Green leaves or the green parts of variegated leaves yielded more radioactivity than the yellow leaf material. BA was metabolized much faster than the endogenous cytokinin tZ. It would appear that while lower amounts of radioactivity were present in yellow leaves, as well as in yellow parts of variegated leaves, the rate of cytokinin metabolism was nevertheless faster. Metabolites that were formed to a greater extent in these yellow parts were the nucleotides of both cytokinins. Currently it is not known whether or not cytokinins influence chlorophyll and other pigment development in chimeric variegated l

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1994.tb02194.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

The increased supply of photosynthate from maternal tissue is known to promote grain growth in several crop species. However, the effect of increasing photosynthate supply on grain growth receives little attention in rice. This study was aimed at evaluating the effect of increasing photosynthate supply through CO2enrichment (650 μl I‐1) on grain growth in three rice cultivars differing in grain size. CO2enrichment was applied to the pot‐grown plants between anthesis and final harvest. The results indicated that high CO2treatment enhanced the CO2exchange rate of leaf tissue, and subsequently increased the sucrose level of peduncle exudate, but it did not promote starch accumulation in the developing grains. This phenomenon was linked to the poor CO2responses for the grain activities of sucrose synthase, UDP‐glucose pyrophosphorylase. ADP‐glucose pyrophosphorylase, and starch synthases involved in the conversion of sucrose to starch. Significant cultivar differences also existed for the activities of sucrose to starch conversion enzymes with larger grain size cultivars tending to have higher enzymes activities (expressed on a grain basis), resulting in a greater carbohydrate accu

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1994.tb02195.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

Nitrogen‐fixing (effective) nodules from various legume‐Rhizobiumcombinations were analyzed for trehalose and other soluble carbohydrates using gas chromatography and for trehalase activity using biochemical assays. Whereas the bacterial disaccharide trehalose was present only in the minority of the nodules, trehalase activity was found in all of them. Extracts from determinate nodules had a higher trehalase activity than extracts from indeterminate nodules. More detailed studies were done on soybean nodules formed in interactions with two effective and 5 ineffectiveBradyrhizobium japonicumstrains. Only in effective soybean nodules colonized by the strain 61‐A‐101 was trehalose a major soluble carbohydrate. Irrespective of the wildtype strains used. effective soybean nodules contained about 10 nkat trehalase g−1fresh weight, whereas the ineffective nodules colonized by mutant strains derived from these wildtype strains contained 2 to 30 times less trehalase. However, a clear correlation between trehalose content and trehalase activity could not be es

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1994.tb02196.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

Light interception, stomatal conductance and chlorophyll fluorescence were measured in potato (Solanum tuberosumL.) grown either irrigated, or droughted from the time of plant emergence. Compared with the irrigated treatment, drought reduced both light interception and stomatal conductance. In both treatments, the yields of variable fluorescence in the dark‐ and light‐adapted states (Fy/Fmand F′v/F′m, respectively) were negatively correlated with photosynthetic photon flux density (PPFD) and mirrored daytime changes in PPFD. Photochemical quenching was positively correlated with PPFD, but the dominant effect of F′v/F′mresulted in a decrease in the quantum yield of photosystem II (PSII) electron transport with increasing PPFD.Drought had no significant effect on the functioning of PSII and the balance between photochemical and non‐photochemical quenching was unaffected. Non‐photochemical quenching was not increased by drought and the quantum yield of PSII electron transport was unaffected. It is concluded that, in leaves of droughted plants, excess energy, resultant of stomatal limitation of photosynthesis, was dissipated by photochemical quenching such as increased p

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1994.tb02197.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

Oscillatory changes of the electrical resistance across the nodal complex ofNitellopsis obtusa(Desv. in Lois) J. Gr. were observed in experiments performed for 40–150 min with the use of external electrodes and microelectrodes. Three main patterns of node resistance oscillations were similar to those found for membrane potential and resistance. The presented findings indicate an oscillatory behaviour of the plasmodesmata system at the node, which may be connected with e.g. pulsatile variations in the number of open plasmodesmat

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1994.tb02198.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

In areas with short growing seasons, poor early vegetative growth of soybean (Glycine max[L.] Merr.) is often attributed to the restrictive effect of cool soil conditions on nodulation and N2‐fixation by this subtropical grain legume. However, there are few studies regarding potential genetic variability of soybean andBradyrhizobium japonicumgenotypes for nodulation at cool root‐zone temperatures (RZT). Experiments were conducted to (1) test for a threshold temperature for low RZT inhibition of soybean nodulation and (2) ascertain whether this threshold temperature response depends mainly on the micro‐ or macrosymbiont. In experiment 1 soybean seedlings (Glycine max[L.] Merr. cv. Maple Arrow) were inoculated with 1 ml of a log phase culture ofB. japonicumstrain 532C, H8 or H15 (the latter two strains were isolated from cold soils of Hokkaido, northern Japan) and maintained at either 16, 17.5, 19 or 25°C RZT. In experiment 2 seedlings of cv. Maple Arrow and a cold‐tolerant Evans isoline were combined with strain 532C and two Hokkaido strains (H5, H30) at both 19 and 25°C RZT. Results indicated that N2‐fixation at 44 days after inoculation was substantially reduced (30–40%) by RZT as high as 19°C, due to development of less nodule mass and to a delay in the onset of N2‐fixation and a small decrease in the number of nodules formed. However, the number of nodules formed was sharply reduced and the time required for the first appearance of nodules was significantly delayed below an RZT of 17.5°C. Differences between cultivars for nodulation and N accumulation were apparent at 25°C, but were abolished by growth at 19°C, indicating that, in spite of differences in growth potential between the cultivars under optimum RZT, both cultivars were equally limited by low RZT. Differences betweenB. japonicumstrains were consistent across temperatures and were largely attributable to higher rates of specific nodule activity recorded for strain 532C, which seemed well adapted to low RZT. These results suggest that the host plant mediates the sensitivity of N2‐fixation under low RZT and that inoculation withB. japonicumstrains from cold environments is unlikely to enhance soybean N2‐fixation und

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1994.tb02199.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

Studied with the fluorochrome 3,3‐dihexyloxacarbocyanine iodide [(DIOC6(3)], the dynamic system of the endoplasmic reticulum (ER) in epidermal cells of onion bulb scales consists of long, tubular strands moving together with organelles in the deeper cytoplasm, and of a less mobile network composed of tubular and lamellar elements at the cell periphery. Treatment with the sulfhydryl‐reagent N‐ethylmaleimide (NEM) inhibited organelle and ER movement, and caused the fusion of ER‐tubules into flat sheets. Fixed, long, tubular ER strands were formed by lowering the cytosolic pH of NEM‐treated cells. Both these observations indicate the involvement of myosin in the dynamics of organelles and ER. Using a monoclonal antibody against murine skeletal muscle myosin (known to cross‐react with plant myosin; Tang et al. 1989, J. Cell Sci. 92: 569–574), myosin was identified by immunofluorescence microscopy. Mapping the distribution of myosin, actin filaments, ER, and organelles in different phases of recovery after centrifugation of epidermal cells, co‐localization of myosin with ER and organelles but not with actin filaments was observed, supporting the hypothesis that a membrane bound motor protein exists in onion epidermal cells, which translocates organelles and the endoplasmic reticulum along

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1994.tb02200.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

The oxidation of putrescine and spermidine were studied in embryogenic and nonembryogenic cell cultures ofPicea abies(L.) Karst., with [1,4‐14C]‐putrescine and [1,4‐14C]‐spermidine as substrates. Activities of putrescine and spermidine oxidation varied at every developmental stage in both cultures. Putrescine was oxidized ca 5 times as fast both in embryogenic and non‐embryogenic tissue as spermidine. Diamine and especially polyamine oxidase activity increased markedly in both tissues towards the end of the culturing. In maturing embryos and in ageing non‐embryogenic cultures, enzyme activities were lower than in non‐differentiated embryogenic calli. Aminoguanidine (1 mM) inhibited di‐ and polyamine oxidation in non‐embryogenic tissue by>60% and>30%, respectively. The pH optimum for putrescine oxidation was 8.0, but in non‐embryogenic tissue spermidine was degraded even more actively at pH 5.0. [14C]‐Spermidine was catabolized to [14C]‐putrescine. Pyrroline dehydrogenase activity was observed in non‐embryogen

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1994.tb02201.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

Two herbaceous perennials, alfalfa (Medicago sativaL. cv. Arc) and orchard grass (Dactylus glomerataL. cv. Potomac), were grown at ambient (367 μmol mol−1) and elevated (729 μmol mol−1) CO2concentrations at constant temperatures of 15, 20, 25 and 30°C in order to examine direct and indirect changes in nighttime CO2efflux rate (respiration) of single leaves. Direct (biochemical) effects of CO2on nighttime respiration were determined for each growth condition by brief (<30 min) exposure to each CO2concentration. If no direct inhibition of respiration was observed, then long‐term reductions in CO2efflux between CO2treatments were presumed to be due to indirect inhibition, probably related to long‐term changes in leaf composition. By this criterion, indirect effects of CO2on leaf respiration were observed at 15 and 20°C forM. sativaon a weight basis, but not on a leaf area or protein basis. Direct effects however, were observed at 15, 20 and 25°C inD. glomerata; therefore the observed reductions in respiration for leaves grown and measured at elevated relative to ambient CO2concentrations could not be distinguished as indirect inhibition. No inhibition of respiration at elevated CO2was observed at the highest growth temperature (30°C) in either species. CO2efflux increased with measurement and growth temperature forM. sativaat both CO2concentrations; however, CO2efflux inD. glomeratashowed complete acclimation to growth temperature. Stimulation of leaf area and weight by elevated CO2levels declined with growth temperature in both species. Data from the present study suggest that both direct and indirect inhibition of respiration are possible with future increases in atmospheric CO2, and that the degree of each type of respiratory inhibition is a function of growt

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1994.tb02202.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

The effects of the acylcyclohexanedione‐type growth retardant prohexadione calcium on seedling growth and endogenous levels of immunoreactive phytohormone‐like substances in shoots of wheat (Triticum aestivumL. cv. Kanzler) and oilseed rape (Brassica napusL. ssp.napuscv. Lirajet) were studied. After treatment of seedlings with increasing retardant concentrations in hydroponics, plant height and fresh weight of shoots were reduced by up to 40%. Concomitantly, the amount of immunoreactive gibberellins decreased, on a fresh weight basis, when compared with levels in the shoots of control plants. In contrast, the levels of abscisic acid and dihydrozeatin riboside and isopentenyladenosine‐type cytokinins were considerably elevated by the growth retardant. The content of 3‐indoleacetic acid decreased slightly. These results suggest that, in addition to its effect on gibberellin content, prohexadione calcium also influences the levels of endogenous abscisic acid and cyt

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1994.tb02203.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY