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41.
The promoting effect of light and alternating temperatures on the germination of seeds of three contrasting populations of Dactylis glomerata L. was studied. Irradiation treatments using broad band low irradiance light sources resulted in red/far-red reversible effects, demonstrating the involvement of phytochrome in germination control. Reduction of germination by far-red below the level of a dark control indicated the presence of high pre-existing levels of the active form of phytochrome (Pfr ) in some individuals. The capacity for dark germination at 21/11°C (12 h/12 h) was shown to be dependent on Pfr . Although some individuals were capable of germination at constant temperatures following red irradiation, in most seeds germination was dependent on the presence of Pfr and alternating temperatures. Some individuals responded to a single red irradiation, although a large proportion of seeds required high levels of Pfr to be maintained for long periods. Previously published dose response curves for alternating temperatures and a measured dark reversion time of 48 h for Pfr established by a single 60 min red irradiation, provided firm evidence of a direct correlation between the requirements for repeated irradiation and number of alternating temperature cycles. 相似文献
42.
Takashi Iwayama 《Cell and tissue research》1970,110(4):487-495
Summary Taste buds of rabbit foliate papillae were observed in control, after denervation and during reinnervation by the glossopharyngeal nerve. In control, taste bud cells could be divided into three groups according to their shapes and staining characteristics. Most of the cells were identified as either dark (corresponding to gustatory) or light (corresponding to supporting) cells. However, some cells were encountered which could not readily be placed in either group; they have been termed intermediate cells. Nine to twelve hours after axotomy, wandering cells were observed in many of the taste buds. Thereafter taste buds gradually decreased in size and disappeared, for the most part, by the 14th postoperative day. It was found that dark cells disappeared first, then at a later stage the light cells also disappeared. During reinnervation, dark cells were first to appear about 40 days after the operation and light cells were not seen till about 9 days later.From the observations, it is concluded that the dark cells of the taste bud differentiate from epithelial cells under the influence of nerves and mature into light cells through intermediate cells. 相似文献
43.
Accumulation of chlorophyll and protochlorophyllide (PChlide) was followed during beterotrophic growth of the pigment mutant C-2A' of Scenedesmus obliquus L. in the darkness at 30 and 20°C. At 30°C the cells remained yellow with accumulation of protochlorophyllide, whereas they became green at 20°C with only traces of protochlorophyllide. The capacity of mutant cells to reduce PChlide to chlorophyllide (Chlide) in the dark with or without addition of 5-aminolevulinic acid as measured in isolated membranes, was high in cells grown at 20°C but negligible at 30°C. The high capacity to reduce PChlide created in cells growing at 20°C was only slightly diminished by exposure of cells to 38°C for 3 h. Mechanisms of temperature-sensitive chlorosis in algae and higher plants are discussed in relation to the results with pigment mutant C-2A' of Scenedesmus obliquus . It is assumed that either an activator of NADPH protochlorophyllide oxidoreductase (EC 1.6.99.1) or a different enzyme system can be activated by lower temperature as by light. 相似文献
44.
Various factors affect the CO2 compensation point of detached leaves of Lolium perenne L. These include oxygen concentration, temperature, leaf age, and season (spring and summer). Analysis of the results using the model of G.D. Farquhar, S. von Caemmerer and J.A. Berry (1980) Planta 149, 78–90, indicates that some of the CO2 evolved by leaves in the light is derived from sources other than photorespiration. It is suggested that the operation of the tricarboxylic acid in the light can account for most of this CO2.Azcón-Bieto—experimental work was done in Barcelona, the further analyses white at the A.N.U. 相似文献
45.
46.
A mass spectrometric 16O2/18O2-isotope technique was used to analyse the rates of gross O2 evolution, net O2 evolution and gross O2 uptake in relation to photon fluence rate by Dunaliella tertiolecta adapted to 0.5, 1.0, 1.5, 2.0 and 2.5 M NaCl at 25°C and pH 7.0.At concentrations of dissolved inorganic carbon saturating for photosynthesis (200 M) gross O2 evolution and net O2 evolution increased with increasing salinity as well as with photon fluence rate. Light compensation was also enhanced with increased salinities. Light saturation of net O2 evolution was reached at about 1000 mol m-2s-1 for all salt concentrations tested. Gross O2 uptake in the light was increased in relation to the NaCl concentration but it was decreased with increasing photon fluence rate for almost all salinities, although an enhanced flow of light generated electrons was simultaneously observed. In addition, a comparison between gross O2 uptake at 1000 mol photons m-2s-1, dark respiration before illumination and immediately after darkening of each experiment showed that gross O2 uptake in the light paralleled but was lower than mitochondrial O2 consumption in the dark.From these results it is suggested that O2 uptake by Dunaliella tertiolecta in the light is mainly influenced by mitochondrial O2 uptake. Therefore, it appears that the light dependent inhibition of gross O2 uptake is caused by a reduction in mitochondrial O2 consumption by light.Abbreviations DCMU
3-(3, 4-dichlorophenyl)-1, 1-dimethylurea
- DHAP
dihydroxy-acetonephosphate
- DIC
dissolved inorganic carbon
- DRa
rate of dark respiration immediately after illumination
- DRb
rate of dark respiration before illumination
- E0
rate of gross oxygen evolution in the light
- NET
rate of net oxygen evolution in the light
- PFR
photon fluence rate
- RubP
rubulose-1,5-bisphosphate
- SHAM
salicyl hydroxamic acid
- U0
rate of gross oxygen uptake in the light 相似文献
47.
Summary In this study, we determined whether relationships existed between dark respiration and genotype at five enzyme polymorphisms in perennial ryegrass, Lolium perenne L. Positive correlations were found between Q
10 of dark respiration and genotype at the phosphoglucomutase (PGM) and 6-phosphogluconate dehydrogenase (6PGD) loci. Plants doubly homozygous for the common allele at these loci were found to have Q
10 values 20% higher than those for double heterozygotes. In plants that were heat stressed for five consecutive days, Q
10 was found to be negatively correlated with apparent vigor after stressing. Individuals homozygous for PGM and 6PGD (with higher Q
10 values) exhibited more apparent damage following the stress than heterozygous individuals. Both PGM and 6PGD occupy positions in metabolism with regulatory potential. Although caution must be used in assigning causal relationships, the results suggest that specific forms of these enzymes are directly related to, or are correlated with, the determinants of respiratory efficiency in L. perenne. 相似文献
48.
《Fungal Ecology》2022
Plants host multiple symbionts that interact with each other affecting plant performance and regulating their establishment. Here, we analyzed how the association with Epichloë endophytes affects belowground colonization by Dark Septate Endophytes (DSE) and arbuscular mycorrhizal fungi (AMF) in the grass Bromus auleticus. Epichloë-symbiotic (E+) and Epichloë-non symbiotic (E−) plants were sampled from a long-term experimental plot and colonization structures were analyzed in the roots. We also examined the influence of Epichloë exudates on the in vitro growth of DSE Microdochium bolleyi isolated from roots. Epichloë symbiosis increased AMF colonization, although differences were not significant. Despite the lack of differences in total DSE colonization, in concordance with in vitro findings, a higher significant abundance of microsclerotia was observed in E+ plants. A negative correlation between total mycorrhizal and DSE was found. Our findings show a more uniform root colonization pattern in E+ plants, suggesting a root symbiosis modulating role. 相似文献
49.
During an extended search in Western Canada for fungal root endophytes useful as biocontrol agents against soil-borne pathogens,
we isolated Heteroconium chaetospira, as well as Phialocephala fortinii or similar taxa, from seven samples of forest soil using herbaceous seedlings of four different species (i.e., barley, Chinese
cabbage, eggplant, and melon) as bait plants. Our results support a previous observation that eggplant is a particularly effective
species for baiting H. chaetospira from soil and confirm the ability of this fungus to grow as an endophyte in the roots of axenically reared host plants. Cultural
characters show that this species is similar to P. fortinii and other melanized fungi in the dark septate endophyte (DSE) group (e.g., Leptodontidium orchidicola, P. sphaeroides, and Cadophora finlandica) in that it produces darkly pigmented colonies on agar media. Heteroconium chaetospira differs from P. fortinii and other melanized members of the Leotiomycetes in the DSE group in that its conidia are fusiform and develop in blastic
acropetal chains. Heteroconium chaetospira is phylogenetically distant from most DSE taxa because DNA sequences for the nuclear small subunit (SSU) ribosomal RNA gene
(rDNA) indicate that the taxon is affiliated with the Herpotrichiellaceae of the Chaetothyriales rather than with the Leotiomycetes. 相似文献
50.
Lulwoana sp., a dark septate endophyte in roots of Posidonia oceanica (L.) Delile seagrass 下载免费PDF全文
L. Torta S. Lo Piccolo G. Piazza S. Burruano P. Colombo D. Ottonello R. Perrone G. Di Maida M. Pirrotta A. Tomasello S. Calvo 《Plant biology (Stuttgart, Germany)》2015,17(2):505-511
Posidonia oceanica is the most common, widespread and important monocotyledon seagrass in the Mediterranean Basin, and hosts a large biodiversity of species, including microorganisms with key roles in the marine environment. In this study, we ascertain the presence of a fungal endophyte in the roots of P. oceanica growing on different substrata (rock, sand and matte) in two Sicilian marine meadows. Staining techniques on root fragments and sections, in combination with microscope observations, were used to visualise the fungal presence and determine the percentage of fungal colonisation (FC) in this tissue. In root fragments, statistical analysis of the FC showed a higher mean in roots anchored on rock than on matte and sand. In root sections, an inter‐ and intracellular septate mycelium, producing intracellular microsclerotia, was detected from the rhizodermis to the vascular cylinder. Using isolation techniques, we obtained, from both sampling sites, sterile, slow‐growing fungal colonies, dark in colour, with septate mycelium, belonging to the dark septate endophytes (DSEs). DNA sequencing of the internal transcribed spacer (ITS) region identified these colonies as Lulwoana sp. To our knowledge, this is the first report of Lulwoana sp. as DSE in roots of P. oceanica. Moreover, the highest fungal colonisation, detected in P. oceanica roots growing on rock, suggests that the presence of the DSE may help the host in several ways, particularly in capturing mineral nutrients through lytic activity. 相似文献