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141.
Root removal enhances flowering in the short day plant Chenopodium rubrum. The extent of this effect depends on the de-rooting time with respect to photoperiodic induction. The largest promotive effect
is observed when de-rooting coincides with the start of the inductive treatment or, to a lesser extent, when performed before
it. De-rooting 24 h after induction has no effect on flowering. The flower-inducing action of de-rooting 24 h before the start
of induction is increased by benzylaminopurine (BAP), whether applied simultaneously with de-rooting or 24 h later. At the
beginning of darkness, BAP inhibits flowering slightly when applied simultaneously with de-rooting but inhibits it strongly
when applied 24 h later. Flowering in plants de-rooted 24 h after induction is inhibited strongly by BAP. Root removal at
the beginning of inductive darkness does not change the level of endogenous cytokinins in induced shoot explants, but under
continuous light the level of cytokinins in shoot explants decreases during the same period compared with the level in the
shoots of intact plants. BAP does not affect the level of endogenous cytokinins in light but causes an apparent increase in
induced segments. Thus, two phases of the de-rooting effect and cytokinin treatment may be distinguished: one in which flowering
is enhanced by both treatments and which is linked directly to photoperiodic flower induction, and the other in which both
treatments are inhibitory to flowering and which is related to morphogenetic events following induction. The time courses
of the effectiveness of de-rooting and BAP treatment differ slightly, suggesting that the effect of de-rooting cannot be attributed
solely to cytokinin deprivation.
Received February 27, 1998; accepted March 3, 1998 相似文献
142.
《Bioscience, biotechnology, and biochemistry》2013,77(4):884-887
The hydrolysis of the bacterial spore peptidoglycan (cortex) is a crucial event in spore germination. It has been suggested that SleC and SleM, which are conserved among clostridia, are to be considered putative cortex-lytic enzymes in Clostridium perfringens. However, little is known about the details of the hydrolytic process by these enzymes during germination, except that SleM functions as a muramidase. Muropeptides derived from SleC-digested decoated spores of a Bacillus subtilis mutant that lacks the enzymes, SleB, YaaH and CwlJ, related to cortex hydrolysis were identified by amino acid analysis and mass spectrometry. The results suggest that SleC is most likely a bifunctional enzyme possessing lytic transglycosylase activity and N-acetylmuramoyl-L-alanine amidase activity confined to cross-linked tetrapeptide-tetrapeptide moieties of the cortex structure. Furthermore, it appears that during germination of Clostridium perfringens spores, SleC causes merely small and local changes in the cortex structure, which are necessary before SleM can function. 相似文献
143.
Background and Aims
In mature quinoa (Chenopodium quinoa) seeds, the lasting endosperm forms a micropylar cone covering the radicle. The suspensor cells lie within the centre of the cone. During the final stage of seed development, the cells of the lasting endosperm accumulate protein and lipids while the rest are crushed and disintegrated. Both the suspensor and endosperm die progressively from the innermost layers surrounding the embryo and extending towards the nucellar tissue. Ricinosomes are endoplasmic reticulum-derived organelles that accumulate both the pro-form and the mature form of cysteine endopeptidase (Cys-EP), first identified in castor bean (Ricinus communis) endosperm during germination. This study sought to identify associations between the presence of ricinosomes and programmed cell death (PCD) hallmarks in suspensor and endosperm cells predestined to die during quinoa seed development.Methods
A structural study using light microscopy and transmission electron microscopy was performed. To detect the presence of Cys-EP, both western blot and in situ immunolocalization assays were carried out using anti-R. communis Cys-EP antibody. A TUNEL assay was used to determine DNA fragmentation.Results and Conclusions
Except for the one or two cell layers that constitute the lasting endosperm in the mature seed, ricinosomes were found in suspensor and endosperm cells. These cells were also the site of morphological abnormalities, including misshapen and fragmented nuclei, vesiculation of the cytosol, vacuole collapse and cell wall disorganization. It is proposed that, in suspensor and endosperm cells, the early detection of Cys-EP in ricinosomes predicts the occurrence of PCD during late seed development. 相似文献144.
《Journal of Plant Interactions》2013,8(1):412-417
Cell suspension cultures of Linum album Kotschy ex Boiss. have been reported to produce anticancer podophyllotoxin and its related lignans. In the present study, we investigated the effect of culture filtrate of Fusarium graminearumon growth, and lignan and phenolic compounds in L. album cell culture. After 7 days of pre-culture, the cells were treated with 1% (v/v) of the culture filtrate. Cell growth was reduced, while phodophyllotoxin and lariciresinol production was stimulated reaching a maximum 0.0187 mg/g fresh weight (FW) and 0.0136 mg/g FW 5 days after the treatment, respectively. Also, our results provide evidence that the culture filtrate of F. graminearum can be effective on phenylalanine ammonia-lyase activity and phenolic compounds. 相似文献
145.
Leonor Álvarez-Cansino María Zunzunegui Mari Cruz Díaz Barradas Otilia Correia Mari Paz Esquivias 《Population Ecology》2013,55(1):135-146
The effects of climate (precipitation and temperature) on sexual dimorphism and population structure were analysed along a broad-scale environmental gradient covering the distributional range of the endemic dioecious species Corema album, along the west coast of the Iberian Peninsula. We aimed to assess distribution constraints and sex-related differences in demography and size associated with higher reproductive investment in females. Nine populations were chosen from across the geographic range of C. album and ten 10 × 10 m plots were established (10 m apart) along a 200-m transect. All male, female and non-reproductive shrubs were quantified within each plot and plant size, photosynthetic layer, height, sex ratio, population density and structure, and spatial segregation of sexes, under environmental conditions ranging from temperate to Mediterranean climate, were recorded and analysed. Increased aridity was related to lower population density and less structured populations, indicating an effect of higher temperature and lower precipitation on regeneration. Sexual dimorphism was influenced by climate, with size differences between sexes varying with aridity. However, demographic differences between sexes reflected in sex ratio deviations or the occurrence of spatial segregation were unrelated to any climatic variable, suggesting the existence of compensatory mechanisms that may counterbalance the higher reproductive effort of female plants. The results show the vulnerability of this endemic species to the increase in aridity expected in the southernmost limit of the biogeographical area due to global climate change, and demonstrate the importance of broad scale studies in the assessment of sexual dimorphism. 相似文献
146.
为明确昆诺阿藜链格孢叶斑病病原,在山西省昆诺阿藜种植区采集典型症状的标本分离病原菌,选择代表性菌株LGB-b和LGB-h对其形态学、分子生物学、致病性及生物学特性进行了研究。综合形态学和多基因系统发育(Alt a 1、endoPG 和OPA10-2)分析,确定昆诺阿藜链格孢叶斑病病原为Alternaria alternata。致病性测定发现接种6 d后病斑呈灰绿至黄绿色,表面具有灰棕至灰褐色霉层,周围具黄绿色晕圈,与田间症状基本一致。菌株LGB-b和LGB-h均可侵染昆诺阿藜、藜和台湾藜。菌株LGB-b菌丝生长的最适培养基为V8 蔬菜汁琼脂培养基(V8)、温度为25-30 ℃、水活度≥0.98、pH为6-7;分生孢子萌发的最适水活度≥0.98、pH为6-7。菌株LGB-h菌丝生长的最适培养基为马铃薯胡萝卜琼脂培养基(PCA)、温度为20-25 ℃、水活度≥0.98、pH为6-7;分生孢子萌发的最适水活度≥0.98、pH为7-8。 相似文献
147.
干旱胁迫下藜的光合特性研究 总被引:3,自引:1,他引:2
通过人工控制水分模拟干旱来研究生长期的藜对干旱胁迫的生理生化反应,以期望为干旱农业的高效生产提供理论依据。以盆栽的藜为材料,用称重控制浇水的方法,研究了干旱胁迫对藜叶片的光合特性。结果表明:干旱胁迫下藜的光合日变化呈双峰型,有“午休”现象(13:00)且受气孔限制;最大净光合速率出现在上午8:00。与正常条件下生长的藜相比,干旱胁迫下藜的光饱和点(LSP)、最大净光合速率(Pn)、表观量子效率(AQY)、二氧化碳饱和点(CSP)和羧化效率(CE)均降低,分别为1 200 μmolphoton·m-2·s-1、8.01 μmol CO2·m-2·s-1、0.016 1 μmol CO2·mol-1 photons、1 200 μmol CO2·mol-1、0.017 6 μmol CO2·m-2·s-1;光补偿点(LCP)、二氧化碳补偿点(CCP)升高,分别达到44.88 μmol photon·m-2·s-1、和46 μmol CO2·mol-1,干旱使藜的光合能力下降。干旱胁迫下藜的光合能力虽有所下降,但与其它C3植物相比仍具有较强的CO2同化能力。藜是一种耐旱力较强的植物。 相似文献
148.
The effects of an excessive supply of carbohydrates on the photosynthetic apparatus of photoautotrophic suspension cultured cells of Chenopodium rubrum were analysed. Glucose feeding resulted in a massive intracellular accumulation of carbohydrates (glucose, fructose, sucrose and starch) and a delayed but pronounced reduction of the chlorophyll content. Maximum photosynthetic efficiency (determined as relative photon yield of oxygen evolution or calculated from fluorescence parameters) was only slightly affected by this treatment. The maximum values of photosynthetic oxygen evolution and of ribulose-1,5-bisphosphate carboxylase-oxygenase activity also did not change significantly when expressed on a chlorophyll basis, thus indicating that membrane and stroma components were reduced to the same extent. Growth analysis demonstrated that even with an excessive supply of carbohydrates the contribution of photosynthesis to growth was still significant (about 35% of total DW production). The results support the hypothesis that accumulation of carbohydrates leads to a coordinated reduction of the photosynthetic machinery. Comparable changes possibly occur during source/sink transitions in green plant tissues. 相似文献
149.
The effects of Photosystem II inhibiting herbicides, 3-(3,4-dichlorophenyl)-1,1-dimethylurea (diuron), atrazine and two novel
2-benzylamino-1,3,5-triazine compounds, on photosynthetic oxygen evolution and chlorophyll a fluorescence induction were measured in thylakoids isolated from Chenopodium album (wild type and atrazine-resistant plants) and cyanobacterial intact cells. The resistant plants have a mutation of serine
for glycine at position 264 of the D1 protein. Diuron and two members of a novel class of 2-benzylamino-1,3,5-triazine compounds
were almost as active in wild-type as in atrazine-resistant thylakoids, indicating that the benzylamino substitution in the
novel triazines may be important for the lack of resistance in these atrazine-resistant plants. The inhibition by the herbicides
of oxygen evolution in the cyanobacteria was somewhat lower than in the thylakoids of Chenopodium album wild type, probably caused by a slower uptake in the intact cells. The so-called OJIP fluorescence induction curve was measured
during a one second light pulse in the absence and in the presence of high concentrations of the four herbicides. In the presence
of a herbicide we observed an increase of the initial fluorescence at the origin (Fo′), a higher J level, and a decreased
steady state at its P level (Fp). The increase to Fo′ and the decreased leveling Fp are discussed. After dark adaptation about
25% of the reaction centers are in the S0 state of the oxygen evolving complex with an electron on the secondary electron accepting quinone, QB. The addition of a herbicide causes a transfer of the electron on QB to the primary quinone acceptor, QA, and displacement of QB by the herbicide; the reduced QA leads to a higher Fo′. The decrease of Fp in the presence of the herbicides is suggested to be caused by inhibition of the
photo-electrochemical stimulation of the fluorescence yield.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
150.
Photoinhibition has been often evaluated with leaf discs floated on water or placed on wet papers to prevent desiccation.
Under these conditions, there is a possibility that CO2 diffusion is blocked by water, which may lead to reduction in photosynthetic CO2 assimilation. Using Chenopodium album L. grown at two irradiances, photosynthesis, quantum yield of Photosystem II (ΔF/F
m′), non-photochemical quenching (qN), and photoinhibition were compared between detached leaves and leaf discs. In low-light-grown plants, photoinhibition was
greater in leaf discs than in detached leaves, while in high-light-grown plants, there was little difference. Leaf discs showed
lower rates of photosynthesis and ΔF/F
m′, and higher qN. The ΔF/F
m′ in leaf discs increased when leaf discs were exposed to high concentration of CO2, suggesting that CO2 diffusion to chloroplasts was limited in leaf discs floated on water.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献