Effects of plant growth regulators on Hill activity of submerged aquatic plants during induced senescence

Effects of plant growth regulators on Hill activity during induced senescence of leaves of three submerged aquatic plants Vallisneria spiralis L., Hydrilla verticillata (L.f.) Royle and Potamogeton pectinatus L., and a terrestrial plant Spinacia oleracea L. were studied. Hill activity was reduced by 39.3, 42.7, 45.2 and 245.1 μmol DCIP (2,6-dichloroindophenol) (mg chl)^?1h^?1 in Vallisneria, Hydrilla, Potamogeton and Spinacia, respectively. During induced senescence of isolated mature leaves, Hill activity declined with increasing incubation time in all species. Kinetin (0.23 mM) treatment reduced the loss of Hill activity; while both 0.69 mM ehthrel and 0.075 mM ABA treatments decreased it in each species. The effect of kinetin was greatest in Spinacia, followed by Potamogeton, Hydrilla and Vallisneria, while the effect of either ethrel or ABA or both was greatest in Potamogeton, followed by Spinacia, Vallisneria and Hydrilla. Kinetin pre-treatment for an optimal period (12 h) followed by treatment with either ethrel or ABA partially removed the inhibitory effect of the latter on Hill activity. Pre-treatment of tissues with either ethrel or ABA solution, restricted to 12 h, followed by kinetin treatment markedly reduced the promotive effect of kinetin on the Hill activity of these species.     

Effects of antioxidants on senescence and hill activity in three submerged aquatic plants

The antioxidants L-cysteine, ascorbic acid, reduced glutathione and mercaptoethanol in concentrations of 10⁻³–10⁻⁵ M arrested senescence by increasing chlorophyll and protein contents, and by delaying the decline in Hill activity over the control in leaves of three submerged aquatic plants, Potamogeton pectinatus L., Vallisneria spiralis L. and Hydrilla verticillata (L.f.) Royle. The most effective concentration of all antioxidants in increasing these parameters over control values was 10⁻⁴ M during the induction of senescence in these species. The greatest increase in these parameters was observed with glutathione in Potamogeton, with mercaptoethanol in Vallisneria and with ascorbic acid in Hydrilla. The least increase was observed with cysteine in Potamogeton and Vallisneria and with glutathione in Hydrilla. In general, the four antioxidants increased these parameters most in Vallisneria, followed by Potamogeton and Hydrilla. In conclusion, the decline in chlorophyll and protein contents, and Hill activity during senescence may be delayed in these species by antioxidant treatment.     

Effects of plant growth regulators on three wood-rotting polypores

The results of the effects of plant growth regulators, kinetin, gibberellic acid, 3-indoleacetic acid and ethrel (2-chloroethylphosphonic acid) on three wood-rotting polypores,viz. Polyporus palustris, Daedalea flavida andTrarnetes badia, are given. 3-Indoleacetic acid, kinetin and gibberellic acid increased the dry mass and protein, and decreased free amino acids, while ethrel decreased dry mass and protein, and increased free amino acids inP. palustris. All the treatments decreased dry mass and protein, and increased free amino acids inD. flavida. Kinetin decreased dry mass and protein, and increased free amino acids whereas 3-indoleacetic acid, gibberellic acid and ethrel increased dry mass and protein, and decreased free amino acids inT. badia over the control. The effects were most pronounced in the three species upon treatment with 50 μm kinetin, 50 μm gibberellic acid, 50 μm 3-indoleacetic acid and 25 μm ethrel. Among the treatments, the effects of 3-indoleacetic acid were most marked in enhancing growth, measured by dry mass ofT. badia out of the three species studied.     

Chloroplasts and the biosynthesis and catabolism of abscisic acid

Chloroplast preparations from the mesocarp ofPersea gratissima and from light-grown shoots ofPisum sativum were unable to synthesize abscisic acid (ABA) from mevalonolactone, mevalonic acid, or isopentenyl pyrophosphate. Similar plastid preparations transformed [2-¹⁴C]ABA into acidic products that were chromatographically similar to those generated byP. gratissima mesocarp slices and excised shoots ofP. sativum. Attempts to increase ABA catabolism in chloroplast preparations using sedimentation through Percoll to remove associated proteases also reduced the capacity for ABA catabolism, suggesting that such catabolism arose from contaminating, cytoplasmic enzymes. Both lincomycin and chloramphenicol inhibited the catabolism of ABA by excised shoots ofP. sativum but had little effect on either ABA biosynthesis or ABA catabolism in mesocarp fromP. gratissima. These processes were inhibited markedly by cycloheximide.     

Evaluation of some common aquatic macrophytes cultivated in enriched water as possible source of protein and biogas

The biomass production of three common aquatic macrophytes,viz. Azolla pinnata, Eichhornia crassipes andHydrilla verticillata, was high at the prevailing environmental conditions and by the enriched water of River Ganga. The biomass production ofAzolla andEichhornia was positively correlated with the orthophosphate phosphorus and nitrate-nitrogen concentrations of the enriched water. The biomass ofAzolla andHydrilla was positively correlated with the electrical conductivity of the water. The average yield of crude protein was highest in Azolla (8,520 kg.ha^–1.yr^–1), and somewhat lower inEichhornia (6,520 kg.ha^–1.yr^–1). The annual biogas production was highest inEichhornia (44,381 litres), and somewhat lower inAzolla (17,186 litres).     

Growth and carbon utilization by sprouted propagules of two species of submersed rooted aquatic plants grown in darkness

Hydrilla verticillata (L. f.) Royle tubers from monoecious plants andPotamogeton gramineus L. winter buds were sprouted and allowed to grow in the dark for 120 days. We measured plant length and counted the number of leaves at 2–3 day intervals.Hydrilla grew most rapidly during the first 16–17 days andPotamogeton grew most rapidly during the first 16–25 days. Measurement of propagule carbon content over time indicated that cessation of rapid growth coincided with depletion of tuber carbon by one-half forHydrilla. ForPotamogeton, growth was reduced after 16 to 25 days while the winter bud C half-life was 37 days. Calculations indicated thatHydrilla mobilized 49% andPotamogeton 39% of the initial propagule carbon to support growth. In a second experiment, in which plants were grown in substrate the plants grew taller and produced slightly more leaves per plant.Potamogeton removed from darkness after specified time periods, and allowed to grow for 21 days in a greenhouse recovered from 20–30 days in the dark. Similarly treatedHydrilla plants recovered from up to 80 days in the dark.Potamogeton had mobilized 79% of initial C by the time it was unable to recover from the dark treatment. Combined results for both species indicate that the majority of propagule C was utilized in the first 16 to 30 days following sprouting. In conjunction with an understanding propagule sprouting requirements, this information will be useful in the timing of application for management techniques. The U.S. Government right to retain a non-exclusive, royalty-free licence in and to any copyright is acknowledged. The U.S. Government right to retain a non-exclusive, royalty-free licence in and to any copyright is acknowledged.     

Influence de i’acide abscissique sur le transport d’ions inorganiques chez la pomme de terre (solanum tuberosum cv. Bintje). etude comparée avec quelques autres phytohormones

Using detached leaves of potato plants (Solanum tuberosum cv. Bintje) it was shown that abscisic acid (ABA) induced an oriented transport of ions (⁸⁶Rb,³²P and^3SS) towards the hormone-treated leaflet. In order to understand the hormone effect on cell permeability, pretreatment of discs with hormonal solution was conducted. The pretreatment with ABA stimulated the uptake of K⁺ simultaneously with the decrease of efflux. The effect of ABA on ion uptake is compared with the action of other hormones, benzylaminopurine (BAP), gibberellic acid (GA₃) known to act over a long distance transport, too. Three kinds of specificity are underlined: - hormonal specificity (stimulation by ABA and inhibiton by BAP of K⁺ uptake by foliar tissues); - ionic specificity (ABA increase⁸⁶Rb influx, but inhibits³²P and^3SS influx); - tissue specificity shown by a comparative study between foliar tissues (source) and tuber tissues (sink). The autoradiography of foliar discs demonstrated that a treatment of foliar discs can be used, at least for Rb⁺ (K), to study role of ABA in long-distance transport.      

Effect of nitrogen,phosphorus and potassium deficiency on the uptake and mobilization of ions in Bengal gram (Cicer arietinum)

Nitrogen, phosphorus and potassium deficiency reduced the uptake of³²P-phosphate,³⁵S-sulphate,²⁴Na-,⁴²K-,⁴⁵Ca-,⁵⁴Mn-,⁵⁹Fe- and⁶⁵Zn- byCicer arietinum (Bengal gram) cv B-75. Root length, leaf area and dry weight of the tissues were also reduced. Since in several cases, the total contents of the radio nucleides both on per plant and per unit dry weight basis were curtailed, the decrease in uptake of several ions cannot be entirely due to reduced growth rate. The reduction in³²P-phosphate uptake was more severe with nitrogen deficient plants than that in phosphate deficient ones; potassium deficient plants, however, took up⁴²K- as avidly as the control plants. Simultaneously the uptake of³⁵SO^{4 2}- and other cations was affected particularly by nitrogen deficiency. The distribution of radionucleides between the root and shoot portions was also disturbed in several cases by deficiency conditions. The radionucleides taken up accumulated in the young regions as in the case of pea and other dicotyledonous plants. Mobilization of³²P and³⁵S in the reproductive plants was most markedly affected by nitrogen and potassium-deficiency.     

Cyclodextrin production and genetic characterization of cyclodextrin glucanotranferase of <Emphasis Type="Italic">Paenibacillus graminis</Emphasis>

Paenibacillus graminis strains were described recently as cyclodextrin (CD) producers. Cyclodextrins are produced by cyclodextrin glucanotransferase (CGTase) which has not been characterized in P. graminis. Similar amounts of α- and β-CDs were produced by P. graminis (MC22.13) and P. macerans (LMD24.10^T). Primers were designed to sequence the gene encoding CGTase from P. graminis. A phylogenetic tree was constructed and P. graminis CGTase protein showed to be closer (79.4% protein identity) to P. macerans |P31835|. Hybridization studies suggested that the gene encoding CGTase is located in different positions in the genomes of P. macerans and P. graminis.     

Senescence of rice leaves at the vegetative stage as affected by growth substances

In rice (Oryza saliva L. ev. Java), the first (younger) leaf senesced later than the second (older) leaf as shown by the decline in chlorophyll and protein contents. Kinetin treatment significantly retarded senescence of leaves, while abscisic acid (ABA) treatment promoted it. The second leaf exported more³²P to the newly emerged growing leaf at the early stages than the first leaf, which always showed higher retention of³²P than the second one. Kinetin treatment lengthened the duration of³²P export and also increased the retention capacity of both leaves, while ABA had the opposite effect. The second leaf showed a higher depletion of nitrogen and phosphorus but à lower depletion of potassium than the first leaf. Kinetin treatment retarded the decline in nutrient content (N and P) while ABA treatment hastened it. Neither growth substance had any effect on potassium content. The content(s) of endogenous eytokinin-like substance(s) decreased while ABA-like substance(s) increased in the two leaves with senescence: these changes in the second leaf took place earlier than in the first leaf.     

The influence of large water level fluctuations and hurricanes on periphyton and associated nutrient storage in subtropical Lake Okeechobee,USA

The abundance, community structure and nutrient content of periphyton, and the host plant taxa Chara, Hydrilla, Potamogeton, Vallisneria and Scirpus were studied in Lake Okeechobee, USA. Water levels were generally high during the study period (August 2002–January 2006), but substantial fluctuations occurred. All host plant biomass was seasonally variable but only Vallisneria biomass was spatially variable. All submerged plant beds disappeared after the passage of two hurricanes in September 2004, and a third hurricane passed over the lake in October 2005. Periphyton assemblages were statistically separated most by substrate and then by season. Prior to the hurricanes, annual maxima of periphyton biovolumes and those of summer submerged plant coverage coincided. During all study years, the diatom taxa dominated periphyton total biovolumes. Periphyton biomass was generally highest during the summer or prior to the hurricanes (in the case of epiphytes) and was spatially variable in the case of both Scirpus and Vallisneria. Epiphytic nutrient contents within each host plant group seasonally varied except for nitrogen and carbon in the Vallisneria epiphytes. Epipelic nutrient contents were spatially variable and seasonally variable for carbon. Nutrient contents in epipelon were significantly higher than that in Scirpus epiphytes and were similar but lower among all epiphytic communities. The total annual areal potential epiphytic phosphorus storage extrapolated during this study (2.0 × 10⁻⁴ metric tons ha⁻¹ year⁻¹) was underestimated because storage estimates for epipelon, Chara and Hydrilla-associated epiphytes were omitted. The Chara and Hydrilla-associated epiphytic nutrient storage values were omitted because of limited data, whereas the epipelic data may have not been spatially representative. For periphyton biovolume, host substrate type, water level fluctuation and hurricane impacts on host substrates appear to be more important than seasonal variation in such factors as temperature and nutrients. Epiphytic nutrient storage appears to be influenced most by water level fluctuation and hurricane-related impacts, while the host substrate type appears to be a less important factor than it is for periphyton biovolume. Maximum periphyton biomass and high nutrient storage in shallow subtropical and tropical eutrophic lakes may only occur at consistently lower water levels and during infrequent periods of disturbance, which enhance host substrate colonizable area.     

l- andd-alanine transport in brush border membrane vesicles from lepidopteran midgut: Evidence for two transport systems

Summary In brush border membrane vesicles from the midgut ofPhilosamia cynthia larvae (Lepidoptera) thel- andd-alanine uptake is dependent on a potassium gradient and on transmembrane electrical potential difference. Each isomer inhibits the uptake of the other form: inhibition ofl-alanine uptake byd-alanine is competitive, whereas inhibition ofd-alanine uptake byl-alanine is noncompetitive. Transstimulation experiments as well as the different pattern of specificity to cations suggest the existence of two transport systems. Kinetic parameters for the two transporters have been calculated both when K_out>K_in and K_out=K_in.d-alanine is actively transported also by the whole midgut, but it is not metabolized by the intestinal tissue.     

Isolation and characterization of acetonitrile utilizing bacteria

Summary Bacteria utilizing high concentrations of acetonitrile as the sole carbon source were isolated and identified asChromobacterium sp. andPseudomonas aeruginosa. Maximum growth was attained after 96 h of incubation andP. aeruginosa grew slightly faster thanChromobacterium sp. The strains were able to grow and oxidize acetonitrile at concentrations as high as 600 mM. However, higher concentrations inhibited growth and oxygen uptake. Degradation studies with (¹⁴C)acetonitrile indicated 57% of acetonitrile was degraded byPseudomonas aeruginosa as compared to 43% byChromobacterium. The isolates utilized different nitrile compounds as carbon substrates.     

Chloroplasts and the biosynthesis and catabolism of abscisic acid

Chloroplast preparations from the mesocarp ofPersea gratissima and from light-grown shoots ofPisum sativum were unable to synthesize abscisic acid (ABA) from mevalonolactone, mevalonic acid, or isopentenyl pyrophosphate. Similar plastid preparations transformed [2-¹⁴C]ABA into acidic products that were chromatographically similar to those generated byP. gratissima mesocarp slices and excised shoots ofP. sativum. Attempts to increase ABA catabolism in chloroplast preparations using sedimentation through Percoll to remove associated proteases also reduced the capacity for ABA catabolism, suggesting that such catabolism arose from contaminating, cytoplasmic enzymes. Both lincomycin and chloramphenicol inhibited the catabolism of ABA by excised shoots ofP. sativum but had little effect on either ABA biosynthesis or ABA catabolism in mesocarp fromP. gratissima. These processes were inhibited markedly by cycloheximide.     

The role of root-associatedKlebsiella pneumoniae in the nitrogen nutrition ofPoa pratensis andTriticum aestivum as estimated by the method of15N isotope dilution

Summary The technique of¹⁵N isotope dilution was used to verify that nitrogen was fixed and transferred to the plant byKlebsiella pneumoniae strain Pp in association withPoa pratensis orTriticum aestivum. Surface sterilized, sprouting seeds were inoculated withK. pneumoniae and grown in sand in modified Leonard jars. Potassium nitrate enriched with¹⁵N was used to provide N concentrations ranging from 10–40 mg Nl^–1 nutrient solution. After 10–18 weeks the shoots and roots were analyzed separately for dry matter, N content, total N, and atom %¹⁵N excess. The acetylene reduction technique was used to test for the presence of N₂-fixing organisms on the roots. The data from¹⁵N isotope dilution demonstrated that up to 33.8% of N in the shoots ofP. pratensis and 15.9% in those ofT. aestivum were derived from associative N₂ fixation byK. pneumoniae. In most experiments the dry matter yield, N content, and total N yield of the shoots ofP. pratensis were increased byK. pneumoniae inoculation, whereas inoculation had no significant effect on the dry matter yield, N content or total N of the shoots ofT. aestivum.     

Biological Control ofMonilinia laxaandFusarium oxysporumf. sp.lycopersiciby a Lytic Enzyme-ProducingPenicillium purpurogenum

Biological control experiments were conducted with the lytic enzyme-producing fungusPenicillium purpurogenumagainst the plant pathogensMonilinia laxaandFusarium oxysporumf. sp.lycopersici.Applications ofP. purpurogenumto peach shoots previously inoculated withM. laxareduced lesion length and extent of pathogen colonization of shoots by 90 and 80% (P ≤ 0.05), respectively, comparable to the level of disease control obtained with the fungicide captan. Disease severity in tomato plants inoculated withF. oxysporumf. sp.lycopersiciwas decreased by 30% (P ≤ 0.05) with the biological treatment. The fungusP. purpurogenumproduced β-1,3-glucanase and chitinase activities in liquid culture that were inducible by cell walls and live mycelium ofM. laxabut not ofF. oxysporumf. sp.lycopersici.Crude filtrates or crude enzyme preparations ofP. purpurogenumcultures with lytic enzyme activities produced lysis of hyphae and spores ofM. laxaandF. oxysporumf. sp.lycopersici.These lytic effects were strong inM. laxaand ended in complete dissolution of mycelium. The induction of lytic enzymes byM. laxaand the effects of lytic enzymes on mycelia of the pathogens in relation to the different degrees of biological control obtained are discussed.     

Host choice and fitness correlates for conopid flies parasitising bumblebees

Two parasitoid flies,Physocephala rufipes andSicus ferrugineus (Diptera, Conopidae), and their hosts,Bombus spp., coexist at various locations in northwestern Switzerland. A detailed field study showed that both conopid species use the hostB. pascuorum to a similar degree, while the hostB. terr-luc (a pooled category ofB. terrestris andB. lucorum) is more frequently parasitised than expected byS. ferrugineus. The hostB. lapidarius in turn is exclusively used byP. rufipes. Furthermore, hosts ofB. terr-luc andB. pascuorum parasitised byS. ferrugineus were larger than hosts parasitised byP. rufipes, or than those not parasitised. The findings suggest thatS. ferrugineus selects larger hosts and may displaceP. rufipes. Pupal weight, a predictor of adult body size and parasitoid fecundity, is positively correlated with host size and larger pupae are more likely to emerge, while host species had no effect on the probability of emergence in either conopid species. Host species affected pupal weight inS. ferrugineus, but not inP. rufipes, althoughP. rufipes grew larger in hosts of a given size. Daughters emerged from larger pupae than males, but this did not correlate with larger host sizes. These observations add to the scarce knowledge of dipteran parasitoids.     

Micropropagation ofPyrus andCydonia and their responses to Fe-limiting conditions

Appropriate micropropagation regimes were determined for fourPyrus species (P. amygdaliformis Vill.,P. betulaefolia Bunge,P. calleryana Dene., andP. communis L.) andCydonia oblonga L. Shoot multiplication was optimal at 10 or 20M N⁶-benzyladenine and high light intensity (135E m^–2 s^-1). Root formation of thePyrus species was stimulated by exposure of shoots to high levels (10 or 32M) of-indolebutyric acid (IBA) for 7 days or a dip in 10 mM IBA for 15 s, followed by a passage on auxin-free medium.-Naphthaleneacetic acid was more effective than IBA in stimulating rooting ofC. oblonga. The effects of Fe-limiting conditions in vitro were determined by comparing the responses of shoots and rooted plantlets to medium containing FeEDTA or FeSO₄, with or without bicarbonate. Symptoms of Fe deficiency were genotype-dependent and most severe in the presence of FeSO₄ and bicarbonate. Chlorosis was pronounced inCydonia, absent fromP. amygdaliformis andP. communis, and intermediate inP. betulaefolia andP. calleryana, indicating a good correlation between in vitro and field responses. Similar responses were obtained with rooted and unrooted shoots. These findings suggest that in vitro cultures may be used for studies of Fe-chlorosis as well as screening for tolerant rootstocks.     

Variation in needle-trace diameter in respect of needle morphology in five conifer species

Needle traces have been used for revealing historical changes in needle longevity of Pinus sylvestris L. and Picea abies (L.) H. Karst. In this paper we compared the needle-trace diameter of five conifer species [Abies sibirica Ledeb., Picea abies, Pinus sylvestris, Pseudotsuga menziesii (Mirb.) Franco and Taxus baccata L.] in respect of needle size. In case of P. sylvestris, we studied how needle-trace diameter varied among different growing sites and among different shoots within a site, and related that variation to needle morphology and structure. Pinus sylvestris had the greatest diameter of needle traces (mean±SD =233±30 m) followed by T. baccata (141±19 m) and P. menziesii (121±30 m). The smallest needle-trace diameter was in A. sibirica (85±21 m) and P. abies (80±18 m). Among species, the needle-trace diameter was strongly correlated with needle length (r =0.93, P <0.05). Within P. sylvestris, the needle-trace diameter was significantly affected by location (P <0.001) and varied significantly among shoots within a location (P <0.001). The shoots of P. sylvestris which had greater average diameter of needle traces, tended to have longer (r =0.36, P <0.05), wider (r =0.55, P <0.05) and heavier (r =0.64, P <0.05) needles with greater stomatal density (r =0.55, P <0.05). Although our results do not allow the use of needle-trace diameter to predict properties of needle structure at the present stage, they nevertheless indicate general trends and point to a need for further studies.     

Drought acclimation of two deciduous tree species of different layers in a temperate forest canopy

Water-use strategies of Populus tremula and Tilia cordata, and the role of abscisic acid in these strategies, were analysed. P. tremula dominated in the overstorey and T. cordata in the lower layer of the tree canopy of the temperate deciduous forest canopy. Shoot water potential (), bulk-leaf abscisic acid concentration ([ABA]_leaf), abscisic acid concentration in xylem sap ([ABA]_xyl), and rate of stomatal closure following the supply of exogenous ABA (v) decreased acropetally through the whole tree canopy, and foliar water content per area (w), concentration of the leaf osmoticum (c), maximum leaf-specific hydraulic conductance of shoot (L), stomatal conductance (g_s), and the threshold dose per leaf area of the exogenous ABA (d_a) required to reduce stomatal conductance increased acropetally through the tree canopy (from the base of the foliage of T. cordata to the top of the foliage of P. tremula) in non-stressed trees. The threshold dose per leaf dry mass of the exogenous ABA (d_w) required to reduce stomatal conductance, was similar through the tree canopy. After a drought period (3 weeks), the , w, L, g_s, d_a and d_w had decreased, and c and v had increased in both species. Yet, the effect of the drought period was more pronounced on L, g_s, d_a, d_w and v in T. cordata, and on , w and c in P. tremula. It was concluded that the water use of the species of the lower canopy layer—T. cordata, is more conservative than that of the species of the overstorey, P. tremula. [ABA]_leaf had not been significantly changed in these trees, and [ABA]_xyl had increased during the drought period only in P. tremula. The relations between [ABA]_leaf, [ABA]_xyl and the stomatal conductance, the osmotic adjustment and the shoot hydraulic conductance are also discussed.