Internode length and anatomical changes in Pisum genotypes crys and cryc in response to extended daylength and applied gibberellin A1

Dwarf pea (Pisum sativum L.) plants with genotypes cry^c and cry^s responded differently when an 8 h photoperiod (8 h daylight, 16 h dark) was extended to 24 h (8 h daylight, 16 h incandescent light). Genotype cry^c showed up to a 4-fold increase in internode length, sustained by increases in both cell length (particularly of epidermal cells) and cell number (particularly of cortical cells) while cry^s plants showed up to a 2-fold increase in internode length sustained mostly by an increase in cell number. Under an 8 h (daylight) photoperiod the two genotypes did not differ in their sensitivity to applied gibberellin A₁ (GA₁) and they showed a similar pattern of response. GA₁ significantly increased internode length, cell length and cell number in both genotypes. Incandescent light did not increase the size of the response to GA₁ except for cry^s plants at high dose rates of GA₁ (29–58 nmol). At saturating doses of GA₁ the two genotypes attained a similar peak internode length; incandescent light increased the peak by about 40%. GA₁ increased the rate of leaf appearance by up to 33% while incandescent light reduced the rate by 4–7%. The elongation response of the more mature internodes of cry^c plants to GA₁ or incandescent light was due primarily to an increase in cell length whereas increased cell number made a significant contribution in the case of internodes which were relatively immature at the time the stimulus was applied. The progressive increase in internode length of both genotypes during ontogeny was due primarily to an increase in cell number. In conclusion, alleles cry^c and cry^s (background le La) do not confer a difference in sensitivity to GA₁ and the increase in internode length in response to incandescent light is probably not the result of a real or perceived increase in GA₁ level. Allele cry^s may partially block a phytochrome mediated response to light and the key difference between genotypes cry^s and cry^c may lie in the greater elongation (extensibility?) of cry^c epidermal cells in incandescent light.     

Oxidation of NADH by plant mitochondria: Kinetics and effects of calcium ions

The kinetics of NADH oxidation by the outer membrane electron transport system of intact beetroot (Beta vulgaris L.) mitochondria were investigated. Very different values for V_max and the K_m for NADH were obtained when either antimycin A-insensitive NADH-cytochrome c activity (V_max= 31 ± 2.5 nmol cytochrome c (mg protein)^?1 min^?1; K_m= 3.1 ± 0.8 μM) or antimycin A-insensitive NADH-ferricyanide activity (V_max= 1.7 ± 0.7 μmol ferricyanide (mg protein)^?1 min^?1; K_m= 83 ± 20 μM) were measured. As ferricyanide is believed to accept electrons closer to the NADH binding site than cytochrome c, it was concluded that 83 ± 20 μM NADH represented a more accurate estimate of the binding affinity of the outer membrane dehydrogenase for NADH. The low K_m determined with NADH-cytochrome c activity may be due to a limitation in electron flow through the components of the outer membrane electron transport chain. The K_m for NADH of the externally-facing inner membrane NADH dehydrogenase of pea leaf (Pisum sativum L. cv. Massey Gem) mitochondria was 26.7 ± 4.3 μM when oxygen was the electron acceptor. At an NADH concentration at which the inner membrane dehydrogenase should predominate, the Ca²⁺ chelator, ethyleneglycol-(β-aminoethylether)-N,N,-tetraacetic acid (EGTA), inhibited the oxidation of NADH through to oxygen and to the ubiquinone-10 analogues, duroquinone and ubiquinone-1, but had no effect on the antimycin A-insensitive ferricyanide reduction. It is concluded that the site of action of Ca²⁺ involves the interaction of the enzyme with ubiquinone and not with NADH.     

Human non-lineage antigen,CD46 (HuLy-m5): purification and partial sequencing demonstrates structural homology with complement-regulating glycoproteins

CD46, until recently known as HuLy-m5, is a non-lineage restricted surface antigen ubiquitously expressed by almost all human cells except erythrocytes. The CD46 antigen is identified by the E4.3 monoclonal antibody (mAb) and exists at the surface of human peripheral blood lymphocytes (PBLs) as two acidic, non-disulfide bonded chains, and , ofM _r 66 000 and 56 000. Receptor density analysis showed that CD46 was of moderately low abundance on PBLs with 7.5×10³ molecules present on each cell. The two chains of CD46 were purified (144 000-fold) by immunoaffinity-chromatography with E4.3 mAb from the plasma membranes of a human spleen infiltrated with chronic myelogenous leukemia cells. Amino acid sequence analysis of the NH₂-terminal of both and chains yielded the same sequence; XEEPPQ/TFEAMELIGKPKPYYEIGE. Peptide mapping studies confirmed that both CD46 chains were closely related, except for one peptide fragment. This amino acid sequence is identical to that of the NH₂-terminal of the recently cloned membrane co-factor protein (MCP), a membrane protein that binds the C3b and C4b fragments of complement and acts as a co-factor for I protein-mediated decay of the complement convertases. CD46 shares a cross-reactive epitope with some primate retroviruses, and this may indicate that some retroviruses mimic the mechanisms used by autologous human cells to evade complement-mediated immune clearance. Offprint requests to: I. F. C. McKenzie.     

Solubilization and Mineralization of Lignin by White Rot Fungi

The white rot fungi Lentinula edodes, Phanerochaete chrysosporium, Pleurotus sajor-caju, Flammulina velutipes, and Schizophyllum commune were grown in liquid media containing ¹⁴C-lignin-labelled wood, and the formation of water-soluble ¹⁴C-labelled products and ¹⁴CO₂, the growth of the fungi, and the activities of extracellular lignin peroxidase, manganese peroxidase, and laccase were measured. Conditions that affect the rate of lignin degradation were imposed, and both long-term (0- to 16-day) and short-term (0- to 72-h) effects on the production of the two types of product and on the activities of the enzymes were monitored. The production of ¹⁴CO₂-labelled products from the aqueous ones was also investigated. The short-term studies showed that the different conditions had different effects on the production of the two products and on the activities of the enzymes. Nitrogen sources inhibited the production of both products by all species when differences in growth could be discounted. Medium pH and manganese affected lignin degradation by the different species differently. With P. chrysosporium, the results were consistent, with lignin peroxidase playing a role in lignin solubilization and manganese peroxidase being important in subsequent CO₂ production.     

The effects of light and temperature on photosynthate partitioning in Antarctic freshwater phytoplankton

The effects of temperature and radiation flux on the partitioningof photosynthetically fixed carbon into four intracellulai metabolicpools was investigated for natural phytoplankton assemblagesfrom an Antarctic freshwater lake. At ambient temperature, proteinsynthesis was saturated at low photon flux densities (30–40µmol m^–2 s^–1) and above this flux fixed carbonwas increasingly stored as lipid and polysaccharide. Increasingtemperature raised both the saturated rate of protein synthesisand the photon flux at which saturation occurred. There wasa corresponding decline in the accumulation of reserve products,particularly at low radiation fluxes. The consequences of thispattern of uptake for the phytoplankton is discussed.     

Developmental regulation of expression of the malate synthase gene in transgenic plants

The cucumber malate synthase (MS) gene, including 1856 bp of 5 non-trnascribed sequence, has been transferred into Petunia (Mitchell) and Nicotiana plumbaginifolia plants using an Agrobacterium binary vector. The transferred gene is found in variable copy number in different transformants, and is stably transmitted in each case as a single Mendelian character. Transgene mRNA accumulates in the seedling during the first three days of germination, then declines in amount as the cotyledons emerge from the seed. The decline is more pronounced in light-grown seedlings than in dark-grown seedlings. Expression of the MS transgene is also detected at a low level in petals of transformed Petunia plants. In these respects the pattern of MS gene expression is similar in cucumber and in trnasformed plants, showing that the transferred DNA fragment contains a functional MS gene. A 1076 bp fragment of 5 sequence was linked to the -glucuronidase reporter gene and transferred into Nicotiana, where it was shown to direct temporal and spatial patterns of expression similar to that of the complete MS gene. However, histochemical localisation of -glucuronidase activity demonstrated that the chimaeric gene is expressed not only in cotyledons of transgenic plants, but also in endosperm and some hypocotyl cells during early germination. The relevance of these findings to the control of malate synthase gene expression is discussed.     

Characteristics and N-terminal amino acid sequence of a manganese peroxidase purified from Lentinula edodes cultures grown on a commercial wood substrate

Summary Extracellular culture filtrates from ligninolytic cultures of the lignin-degrading basidiomycete Lentinula (syn. Lentinus) edodes (Berk.) Pegler contained one major peroxidase when grown on a commercial oak-wood substrate. The peroxidase was purified by polyethylenimine clarification, anion-exchange chromatography, and hydrophobic-interaction HPLC. The enzyme (MnP1) was a heme-iron protein with an apparent molecular weight of 44 600 on sodium dodecyl sulfate-polyacrylamide gel electrophoresis gels and an isoelectric point of pH 3.2. The native enzyme had an absorption maximum at 407 nm, which shifted to 420 nm upon H₂O₂ addition. The pyridine-hemochrome-absorption spectrum indicated that one heme group was present per enzyme as protoporphyrin IX. N-terminal amino acid sequencing showed that MnP1 had higher sequence homology with manganese peroxidases than with lignin peroxidases reported from Phanerochaete chrysosporium. L. edodes MnP1 was capable of oxidizing lignin and lignin-model compounds in the presence of manganese and H₂O₂.On leave from the Department of Biochemistry, University of Otago, P. O. Box 56, Dunedin, New Zealand.Research carried out while a visiting scientist at the USDA Forest Products Laboratory from the National Chemistry Laboratory, Pune, India 41 1008 Offprint requests to: I. T. Forrester     

Distribution and hydraulic significance of large woody debris in a lowland Australian river

The line-intersect technique was used to measure the loading of large woody debris in a 1.8 km reach of the Thomson River, Victoria (catchment area of 3540 km²). A debris census (measuring every item present) was done over 0.775 km of this reach. The transect technique over-estimated the actual loading revealed by the census. The loading of debris 0.01 m in diameter for the total 1.8 km reach was 0.0172 m³ m^–2, which is higher than that measured in many headwater streams in other parts of the world. The volume loading of debris measured from low level aerial photographs was only 4.8% of the value estimated by the line-intersect technique. The line-intersect estimates were biased due to non-random orientation of debris in the stream (causing estimated errors of +8% for volume loading and +16% for surface area loading). It is recommended that to avoid this problem, when using the line-intersect transect technique in lowland rivers, each line should comprise at least two obliquely-angled transects across the channel. The mean item of debris (0.1 m in diameter) had a trunk basal diameter of 0.45 m, a length of 7.4 m, and volume of 0.7 m³. The riparian trees and the in-channel debris were of similar dimensions. The debris tended to be close to the bed and banks and was oriented downstream by the flow at a median angle of 27°. Because of this orientation, most debris had a small projected cross-sectional area, with the median value being only 1 m². Thus, the blockage ratio (proportion of projected area of debris to channel cross-sectional area) was also low, ranging from 0.0002 to 0.1, with a median value of 0.004. The average item of debris, which occupied only 0.4% of the cross-section, would have minimal influence on banktop flow hydraulics, but the largest items, which occupied around 10%, could be significant. Judicious re-introduction of debris into previously cleared rivers is unlikely to result in a large loss of conveyance, or a detectable increase in flooding frequency.     

Black tea,green tea,and tea polyphenols

Previous studies have shown that tea consumption can impair trace element metabolism, particularly iron status, and increase the risk of anemia in humans and animals. More recently, however, evidence has been accumulating to show that, in animals, consumption of green tea or its polyphenols is associated with a reduction of the incidence and severity of a variety of experimentally induced cancers. In this study we have monitored the growth, trace element status, including hematological parameters of weanling rats given either (1) water, (2) 1% black tea, (3) 1% green, tea, or (4) 0.2% crude green tea extract as their sole drinking fluid while consuming diets containing either adequate or low amounts of iron. With the exception of manaanese, none of the trace elements studied (iron, copper, zinc, and manganese) or the hematological indices measured were affected by the type of beverage supplied, even though the polyphenol extract was shown to chelate metals in vitro and all the animals fed the low iron diet were shown to be anemic. There appeared to be an effect of black and green teas on manganese balance in, both the first and last weeks of the study. A lower level of brain managanese was associated with green tea consumption, and a higher level of this element in the kidneys of animals fed black tea. The results demonstrate that both black and green teas and a green tea polyphenol extract do not represent a risk to animals consuming the beverages as their sole fluid intake with respect to iron availability, although the interactions with manganese deserve further study.