In zweijährigen Erhebungen zur Entomofauna an Miscanthus sinensis, Panicwn virgatum und Andropogon gerardii auf Flächen in Grcßbeeren und Güterfelde konnten erste Ergebnisse erzielt werden. Am Standort Güterfelde erfolgten gleichfalls mehrjährige Prüfungen der herbiziden Wirkung bei diesen C4‐Pflanzen. Die Besiedlung der Arthropoden mit 0,5 und 1,4 Individuen/Halm bzw. Horstpflanze erweist sich als sehr gering. Die Dominanz der Schad‐ und Nutzorganismen war im allgenmeinen ausgeglichen. Nur auf den Flächen mit P. virgatum und A. gerardii 1995 in Güterfelde lag der Schädlingsanteil durch die Blasenfüße (Thysanoptera) bei>90%, bedingt auch durch die trockene und warme Witterung im Juli/August. Das Schädlingsspektrum umfaßte Arten von Getreide u.a. Gramineen. Im gleichen Jahr 1995 verursachte die Gemeine Spinnmilbe (Tetranychus urticae) auf der Miscanthusfläche in Großbeeren bemerkenswerte Saugschäden. Das Nützlingsauftreten wurde von euryöken Arten bestimmt und war auf allen untersuchten Flächen gering. Die Untersuchungen zur Unkrautbekämpfung im 1. bzw. 2. Standjahr zeigen, daß Präparate, die erfolgreich bei Mais und teilweise Getreide angewandt werden, auch auf Miscanthusflächen sowie bei Panicum und Andropogon vorrangig in der Nachpflanzanwendung zum Einsatz kommen können. Bedeutung erlangt auch die Anwendung der mechanischen Pflege. Es besteht ein direkter Zusammenhang zwischen der Effektivität der Unkrautbekämpfung im Anpflanzjahr und der Pflanzenentwicklung im Anpflanzjahr und den folgenden Etablierungsjahren. Bei unzureichender Unkrautbeseitigung im 1. Standjahr muß auch im 1. Folgejahr eine Unkrautbekämpfung erfolgen. 相似文献
Natural abundance of 15N ( 15N) of leaves harvested from tropical plants in Brazil and Thailand was analyzed. The 15N values of non-N2-fixing trees in Brazil were +4.5±1.9, which is lower than those of soil nitrogen (+8.0±2.2). In contrast, mimosa and kudzu had very low 15N values (–1.4+0.5). The 15N values of Panicum maximum and leguminous trees, except Leucaena leucocephala, were similar to those of non-N2-fixing trees, suggesting that the contribution of fixed N in these plants is negligible. The 15N values of non-N2-fixing trees in Thailand were +4.9±2.0. Leucaena leucocephala, Sesbania grandiflora, Casuarina spp. and Cycas spp. had low 15N values, close to the value of atmospheric N2 (0), pointing to a major contribution of N2 fixation in these plants. Cassia spp. and Tamarindus indica had high 15N values, which confirms that these species are non-nodulating legumes. The 15N values of Acacia spp. and Gliricidia sepium and other potentially nodulating tree legumes were, on average, slightly lower than those of non-N2-fixing trees, indicating a small contribution of N2 fixation in these legumes. 相似文献
Panicum milioides, a naturally occurring species with C4-like Kranz leaf anatomy, is intermediate between C3 and C4 plants with respect to photorespiration and the associated oxygen inhibition of photosynthesis. This paper presents direct evidence for a limited degree of C4 photosynthesis in this C3-C4 intermediate species based on:
1. (a) the appearance of 24% of the total 14C fixed following 4 s photosynthesis in 14CO2-air by excised leaves in malate and aspartate and the complete transfer of label from the C4 acids to Calvin cycle intermediates within a 15 s chase in 12CO2-air;
2. (b) pyruvate- or alanine-enhanced light-dependent CO2 fixation and pyruvate stimulation of oxaloacetate- or 3-phosphoglycerate-dependent O2 evolution by illuminated mesophyll protoplasts, but not bundle sheath strands; and
3. (c) NAD-malic enzyme-dependent decarboxylation of C4 acids at the C-4 carboxyl position, C4 acid-dependent O2 evolution, and 14CO2 donation from [4-14C]C4 acids to Calvin cycle intermediates during photosynthesis by bundle sheath strands, but not mesophyll protoplasts.
However, P. milioides differs from C4 plants in that the activity of the C4 cycle enzymes is only 15 to 30% of a C4Panicum species and the Calvin cycle and phosphoenolpyruvate carboxylase are present in both cell types. From these and related studies (Rathnam, C.K.M. and Chollet, R. (1979) Arch. Biochem. Biophys. 193, 346–354; (1978) Biochem. Biophys. Res. Commun. 85, 801–808) we conclude that reduced photorespiration in P. milioides is due to a limited degree of NAD-malic enzyme-type C4 photosynthesis permitting an increase in pCO2 at the site of bundle sheath, but not mesophyll, ribulosebisphosphate carboxylase-oxygenase. 相似文献
We have used Western blue-visualized in situ-hybridization (ISH) to monitor the expression of apomixis-specific gene-1 (ASG-1, GenBank accession number AB000809) during gametogenesis in obligate-sexual and facultative-apomictic (aposporic) genotypes of guinea grass (Panicum maximum). The in situ-analysis revealed that ASG-1 is not expressed in the ovule during early floral development in both, the facultative apomicts (A1 stage) and the obligate sexuals (S1 stage). With the appearance of the aposporous initial cell(s) in the ovule of the apomictic type (A2-1 stage), ASG-1 expression is strong and specific to this apomixis-specific cell. ASG-1 expression continued through different stages of aposporous embryo sac development (A2-2 stage), indicating that the gene may play a role in this developmental process. Regular embryo sacs in sexual types did not show hybridization signals (S2 stage). However, strong ASG-1 expression was detected in immature pollen grains and young embryos in both reproductive types, suggesting that ASG-1 may be an allele derived from the obligate-sexual wild type. Expression in pollen grains faded with maturation. In a heterologous system, using Paspalum notatum, a facultative-aposporic tropical grass (bahia grass), identical results were obtained. The results are discussed in view of the fact, that ASG-1 shows some homology to genes known to be seed- or embryo-specific or involved in processes related to cell growth. 相似文献
The potential ecological impacts of switchgrass (Panicum virgatum L.), as a biofuel feedstock, have been assessed under different environmental conditions. However, limited information is available in understanding the integrated analysis of nitrogen (N) dynamics including soil nitrate (), nitrous oxide (N2O) emissions, and leaching under switchgrass land management. The specific objective was to explore N dynamics for 2009 through 2015 in switchgrass seeded to a marginally yielding cropland based on treatments of N fertilization rate (N rate; low, 0; medium, 56; high, 112 kg N ha?1) and landscape position (shoulder, backslope, and footslope). Our findings indicated that N rate impacted soil (0–5 cm depth) and surface N2O fluxes but did not impact leaching during the observed years. Medium N (56 kg N ha?1) was the optimal rate for increasing biomass yield with reduced environmental problems. Landscape position impacted the N dynamics. At the footslope position, soil , soil leaching, and N2O fluxes were higher than the other landscape positions. Soil N2O fluxes and leaching had downward trends over the observed years. Growing switchgrass on marginally yielding croplands can store soil N, reduce N losses via leaching, and mitigate N2O emissions from soils to the atmosphere over the years. Switchgrass seeded on marginally yielding croplands can be beneficial in reducing N losses and can be grown as a sustainable bioenergy crop on these marginal lands. 相似文献
We report the ATP-mediated activation of sucrose-phosphate synthase in bundle sheath cells prepared from C4 species. Sucrose synthesis was followed by measuring the incorporation of [14C]fructose 6-phosphate into sucrose in bundle sheath cells also provided with uridine 5′-diphosphoglucose (UDPGlc). Studies
with Panicum miliaceum L. cells showed that activation was largely due to an increase in the affinity for UDPGlc and was therefore only evident
at limiting UDPGlc concentrations. The apparent Km UDPGlc for sucrose synthesis by cells pretreated and assayed with ATP was about 0.7 mM compared with 7–8 mM for control cells
without ATP. The γ-thio derivative of ATP had a similar effect to ATP. The effect was also evident when ATP was rapidly removed
from cells prior to assay. Sucrose-phosphate synthase activity in extracts from cells pretreated with or without ATP showed
similar differences in Km UDPGlc. These observations support the view that ATP is inducing a covalent modification of the enzyme. However, several
protein kinase inhibitors did not prevent activation. Changes of more than threefold were observed for the Km UDPGlc with sucrose-phosphate synthase extracted from bundle sheath cells rapidly isolated from attached leaves that were
subjected to dark/light treatments. The possible relationship between these changes and those induced by ATP with isolated
cells is discussed.
Received: 22 October 1996 / Accepted: 7 January 1997 相似文献
The objective of this study was to determine the types and concentrations of auxins and cytokinins that would result in effective culture initiation and plant regeneration of switchgrass (Panicum virgatum L.). Whole caryopses and young seedling explants were cultured on MS medium containing different concentrations of picloram or 2,4-dichlorophenoxyacetic acid (2,4-d) in combination with benzyladenine. Best results from mature caryopses were obtained with 11.3–45.0 M 2,4-d in combination with 15.0 or 45.0 M benzyladenine (BA). More than 300 plants were obtained per embryogenic callus from some treatments after the second transfer to regeneration medium (90 days after initiation of the cultures). Regeneration was obtained from young seedling explants with both auxins. However, picloram was more effective over a wider range of BA concentrations than 2,4-d. Protocols developed during this study were used to regenerate hundreds of plants which could easily be established in the field. 相似文献